FAQ: Engine Mounts

How do I CHANGE ENGINE MOUNTS?

Changing Engine Mounts
(For pictures of Ron's lifting of the engine, see At C34 Projects: Changing Engine Mounts page)
Ron Hills Wrote: 
CHANGING ENGINE MOUNTS is an easy task to do. I did it by myself in about 4 hours. With two people, you can easily cut that time in half. I had already removed the bronze drive shaft and was changing it with a stainless shaft so that piece was already disconnected from the engine. At the same time, I was in the process of replacing the Aqua Lift muffler so the exhaust riser going into the single hump hose was also disconnected. With those two items disconnected, I figured there wasn't a better time to tackle the engine mounts. ALL other hoses and wires remained connected.

I removed all four top engine mount nuts and made a template gage of the distance between the bottom of each engine mount bracket and the engine bed. This allowed me to install the new mounts and have them adjusted so they'd be in the ballpark for later checking shaft alignment.

I rigged a 4:1 block and tackle to the aft bail on the boom. The engine and transmission (M25XPA) weighs 309 lbs. Even though I was only lifting half that weight, I wanted to insure I wouldn't put a bow in the boom. I took the main halyard and secured it taught around the boom just aft of the "lifting" bale. The end of the block and tackle was led through the starboard genoa block to the primary winch. To keep the boom centered, I ran another line from the boom to the port side primary winch.

I decided not to use the two lifting eyes on the engine as they are off set and I wanted the engine to rotate straight up, not cocked to one side. I made a lifting bridle (7/16" Dacron) around the forward part of the engine. As the engine lifted up it rotated back on the rear mounts, holding it in place. When it was raised high enough, it was an easy matter to remove the old mounts and slip the new ones in place. There was sufficient room for the exhaust riser (still attached to the engine) to rotate freely. After lowering the engine, I moved the bridle to the
rear of the engine. I lifted it again with the new front mounts keeping the engine in place while I changed the rear mounts. Both times I threaded the top nuts a few turns (on the "keeper mounts") as a just in case.

The hardest part of doing this by yourself is going from the cockpit to the inside without steps or an engine to step on. Would you believe that I swung down on the spinnaker halyard like Tarzan and got back up by a hand over hand climb!?! It's much easier to climb in/out of the V-berth hatch. That's why it's helpful to have a second person below telling the one in the cockpit on the winch, what's happening.

I used Vetus K50 mounts, which are similar to the new style Universal mounts. (The same mounts will work on the M25 Universal.)

1. Make sure the new mount is rated for the engine weight (with transmission) and horsepower.

2. Measure the vertical distance between the engine mount brackets and bed insuring there is sufficient room to accommodate the minimum height of the new mounts you select.

3. The most difficult engine lag bolt to remove was the forward bolt on the port rear mount. I purchased a 9/16" box/open end wrench and cut it in half so I had a "stubby" wrench to work with.

4. Check the length of the lag bolts needed to secure the new mounts. Mine needed bolts 1/2" shorter than the original.

5. If some of the old lag bolt holes are too large, you can use a longer bolt or paint the holes with glass or fast drying epoxy. DON'T fill the hole, as you won't be able to drill it out!

6. Use pieces of leather or chafe guard to protect your lifting bridle.

7. Place your bridle on the EDGES of where the oil pan joins the engine and make sure you are not pinching any wires or hoses.

8. Insure that the mounts you purchase have mounting holes that match (length fore and aft) the existing holes.

9. Look at your existing mounts and note where in the elongated slot the bolt is mounted. I had to do a little "rat tail file" work to elongate that hole in a couple of my mounts.
Although I replaced my mounts while the boat was on the hard for winter storage, there is no reason you couldn't do it in the water. Just remove the four bolts holding the flanges together and slide the drive shaft aft a couple of inches. Removing the riser to muffler inlet hose is tougher if you don't have a hump hose, but still doable. Maybe this is a good time to install and treat your engine to a single hump hose. I found that both of my old portside mounts were absolutely shot (both were oil soaked)!
I can't say enough about the new mounts. It's like I'm on a different boat!! There is no RPM that is smoother than another (above low idle). The buzz in your feet behind the wheel from a long motor and the vibration in the galley floor are GONE. The loudest noise now is the "sploosh, sploosh" of the exhaust water. I received the best compliment ever from another C34 Fleet 12 member. He was getting ready to untie my starboard lines when he asked, "Aren't you going to start your engine?" It was already running at 1200 RPM!!
Since I wrote this article I've had two more incidents where marina personnel have asked the same question, and the engine is already running!!
Ron APACHE #788, ronphylhill@juno.com

Re: Changing Engine Mounts
I used a 4X4 across the companionway and a chain hoist to lift the engine, other than that I used the same procedure. One other thing, if you don't already have a hose attached to the drain plug for pumping out oil, this is
an excellent time to install one.
Cap'n Stan, SPMcHenry@worldnet.att.net

Re: Changing Engine Mounts
Have a few comments: I tried the 3" spreader jaws first. The deck Liner under a C34 is curved and after trying 1"& 2" lumber combinations and having the engine SLIP off the jaws 3 or 4 times I discarded that method. Wasn't too sure how strong the liner is anyway. It may work on a C30, but wouldn't recommend it for a C34.
I thought of using a 4X4, but discarded that way of lifting, as I used what I had on the boat (a chain hoist will work) and was worried about screwing up the teak on the top side with a 4x4 sitting on two other pieces of 4x4s(to stand off from to teak strips). A few thoughts.
Ron APACHE #788, ronphylhill@juno.com

Re: Changing Engine Mounts
Michael,
Allow me to jump in here on this topic. I have used NorShipCo out of Norfolk, Virginia for the Universal brand of mounts as found on the M-25/M-25XP diesel engines installed in the Catalina 30. They are factory engine mounts, pricey, but exactly what is required.
On several occasions I have replaced these mounts using a hydraulic jack to raise the engine. This particular jack is found used in automotive body shops and has various attachment devices. The device I use is a 3" spreader jaw.
It is necessary to remove a good portion of the shelving directly above the rear of the engine for clearance. For course you will disconnect the prop shaft.
Carefully measure and record the height of each engine-mounting bracket from the engine-mounting rail. This dimension is later used to rough in the engine alignment.
I place a "6 by" piece of wood on the bilge floor under the front of the engine and continue stacking wood blocks until the spreader jaws barely slip between the last piece of wood and the oil pan. Loosen and remove the front engine mount locking nuts. Remove the four lag bolts securing the front engine mounts from the rails. Loosen and remove the rear engine mount locking nuts. For stability when raising the engine, DO NOT remove the four lag bolts securing the rear engine mounts from the rails. After that, it's a simple matter to raise the engine and replace the front mounts. Bolt the front mounts to the rails, lower the engine, and do not replace the locking nuts.
Repeat the entire process for the rear mounts.
Liberally application a silicon sealer to the engine mount lag bolts to prevent water from penetrating into the wooden rails.
Align the engine.
Connect the prop shaft coupling.
Done. Takes two hours.
Hope this helps,
Joe

Re: Changing Engine Mounts, Engine Vibrations
The engine in our C34 vibrated very much - it would rattle the wood around the companionway and the galley floor. I ordered the Vetus 50 motor mounts and I installed the mounts yesterday. I rented a 1 ton chain hoist and attached it to a 4 x 4 post across the top of the companionway. The two lift points on the engine are not exactly in the right position to lift the engine up straight but it did the job. I had to use a 2 x 4 as a prybar to get the port forward leg high enough to change. That part of the job took about an hour.
Aligning the engine and checking it out took a little longer. I still have excess vibration at idle. The engine just runs very rough at idle (about 850-900 RPMs). At 1200 RPM the engine smoothes out and there is kind of hammering sound in the hull. At 1400 RPM and above it is smooth and quite.
I did not take the boat out but I did put the boat in forward and reverse and ran the engine up to about 2000 RPM at one point. It was very smooth in forward and reverse except at low RPMs. I am generally pleased with the new motor mounts. I wish I could get the engine to run smooth at idle. Does anyone have a possible fix to a rough running engine at idle.
Joe Turner , C34 # 1039, joet01@bellsouth.net

Re: Changing Engine Mounts
Jim : When you get your Vetus catalog it will have the "K50" mounts listed and will also have flexible couplings listed. In their last catalog I didn't see my UNIFL12 flexible coupling listed. You may have to talk with them about a replacement if it's no longer in stock. Make sure to check if their product is metric and if you need to machine a flange like I had to, to accommodate a 1" shaft. Their stuff is made in Holland and everything is metric - to include the threads and nuts on the engine mounts. The ONLY place to purchase a 1 5/8" single hump hose is from Catalina parts. Watch the sales and you can find a new head for approx. $95. Happy Holidays.
Ron

Chris: Let me answer your questions:
1. Price was only a small part of the selection. Vetus could talk performance data on their mounts and if I had a problem I could back to the guy that made the mounts and get some satisfaction. Don't believe I could have gotten much info out of the "engine" manufacturer when asking a mount question. I have a Vetus Flexible coupling and was very pleased with that product. They also make a number of different mounts so - ONE doesn't fit all.
2. Yes
3. For and aft are exactly the same as the old mount holes. The filing was from side to side, because Catalina screwed up when they originally installed the engine. They managed to get some of the lag bolts all the way over to one side of the old mounts' elongated slot rather than in the center!!! Easier to make the slots longer than to fill and drill more holes in the bed.
Any more questions let me know. Ron

Re: Changing Engine Mounts
Hi Ron, my name is Chris and I am a fellow Catalina 34 owner. I've read a number of your articles and it seems you know more about the 34 than Catalina themselves. I'll get to the point.
I read your article recently regarding engine mount replacement, and will be doing mine in a few weeks while the shaft and riser are off. It's a 1986, hull # 218 (DIONYSUS). My questions are:

1) Why did you choose the Vetus K-50 mount instead of the universal mount? Any reason other than price?

2) Are the mounting holes for the feet of the mounts oblong for side to side adjustment of the engine? In the catalog they appear round, and you did mention something about "rat-tail filing".

3) Was the filing for side-side engine alignment or forward-aft fit of the mount feet?  

Any help on this matter is appreciated. Sincerely,
Chris Peteros, #218-Dionysus, Newport, RI ~~~~~~~_/) ~~~~~~~

Re: Changing Engine Mounts
Vetus offers a mount called "MITSTEVN" and claim that the difference in vibration is "truly staggering." It's good for engines up to 35HP. Anyone have experience with it? Also the PYI Flex coupling claims to handle up to .010 runout. My mind isn't able to calculate how that compares to the 2 deg. that VETUS handles. The VETUS looks nice on the APACHE and I know you swear by it Ron but I'm wondering if anyone has the PYI in operation. I looked at the PYI at the Miami Boat Show and although it looks simple, I didn't see much flex built into it, (I met Joe & Pat Turner also, bought some packing and had a nice chat). I would think that with less vibration being transmitted to the boat via better isolation mounts, more stress is being put on the drivetrain. Has the solid coupling ever failed due to fatigue? Does the cutlass bearing ware more or less?
Anyhow, I'm changing the mounts and I'm leaning to the MITSTEVN because of the "simply staggering" remark, I'm reluctant to be the first one though.
Ron Kash, Rondevou # 315, RK15460@aol.com

Re: Changing Engine Mounts
You must consider the trade-off between flexibility and movement. Don't use bearings that are too soft. Soft bearings allow the engine to move without applying, as much force to the engine beds, and therefore the hull, but the cost is movement. Less force to the hull means less vibration; hence less noise. But unduly soft bearings would allow too much up and down movement at the shaft causing the shaft to hit the shaft tube, regardless of the coupling flexibility. Remember that the shaft clearance in the tube is only about 1/8 inch even if you've properly centered the shaft. Undue flexibility in the fore-aft direction will also cause another problem; propeller thrust is passed through the transmission into the engine and to the hull via the engine mounts. At full power that thrust is maybe 600 to 700 lbf. If the bearings can deflect foreword too much the whole engine, shaft and propeller will move forward. If you look at the shaft at the cutlass bearing you might already see some signs of movement. Further if the bearings are too soft vertically the engine can pitch up at the back and down at the front due to the propeller thrust causing rotation and lifting at the coupling.
So, don't get carried away with installation of soft mounts.
My thrust calculation is approximate, based on ((2/3) x 20 [hp] x 550 [ft-lbf/s]) / (7 [nm/hr] x 6076 [ft/nm] x (1/3600) [hr/s]) = 620 lbf, where 2/3 is an assumed efficiency of power conversion to thrust. My apologies to engineers who have better knowledge of efficiency and to non-engineers for complicating matters with calculations.
Probably the best installation would be to carry the propeller thrust to the hull at a bearing on the shaft with a double universal joint between the thrust bearing and the engine and then use very soft engine mounts. The engine mounts would then only have to prevent the engine moving too much as the boat pitched when sailing. And that system is on the market; they advertise in most sailing magazines. However, we don't have the space to install that type of system. If we could we'd have as quiet an installation as one gets with an onboard genet. In case you weren't aware, many genets are actually based on the same Kobota engine that's used for the 25XP.
I've recently added the R&D bearings (part 800-033) and had previously installed their flexible coupling; both sold by PYI in USA and Canada. I'm very pleased with the result. Now I'm into adding sound absorption material behind the engine and in the head cupboard.
I actually went to R&D's factory north of London to get the mounts. The owner recommended those mounts as opposed to others he makes based on experience and testing. He reported experimenting with the Kobota engine that forms the core of the Universal 25XP to improve its vibration characteristics, finding it could be improved significantly by adding a much heavier flywheel. Unfortunately, that's not a practical proposition for us and the extra weight could overload the crankshaft or its aft bearing, thereby reducing their life expectancy.
From a practical perceptive, you'll find your choice mounts are limited by the space on the engine bed and the clearance between the bed and the engine. On my 1988 C34 with a 25XP it's hard to fit other than a mount with 4-inch bolt-hole centers because there simply isn't enough space on the bed to install a 5-inch mount. And the vertical clearance of, I think, about 2.75" precluded many taller mounts.
Charles Holder, C34 #617, holder@telus.net

Re: Changing Engine Mounts
Ron Kash : Don't be reluctant to be the first, I've been cutting the trail for 12 years and would gladly have someone else take over especially another RON. The Vetus Mitsteun engine mounts really sound great, I hope you can get them under your engine. As you observed the PYI coupling isn't very flexible. You get what you pay for and if you keep your engine within .003" the cheaper PYI will work well. I like the Vetus as I can forget about shaft alignment. I think cutless bearing wear is a combination between engine hours, impurities in the water and shaft alignment. Have never heard of a solid coupling failing.
Ron Hill APACHE #788 ronphylhill@erols.com

A typical boat maintenance weekend I fear:

Task: install new Vetus motor mounts. The vibrations at certain RPMs finally got to me. M35A in a '91 C34. Ron Hills notes on the C34 web site are very good on this by the way.

Changed out the front mounts with no problem. Rear mounts: the old boom vang I tried to use to hoist the engine. Just didn’t have enough purchase (bad planning on my part). The $15 come-a-long sitting in the garage will remedy that next time.

Noticed some black exhaust smoke on the insulation where the exhaust pipe screws into the exhaust manifold. The exhaust pipe is loose enough that I could move it by hand. Will have to disassemble and see if it just needs tightening or if the threads are burned up. Anyone have any experience in this area? Any recommendations? It seems from reading the list the exhaust pipes are SS after certain years? A good time to install the hump hose I assume.

The starboard rear mount looks relatively easy. The port one ?? Not sure I am enough of a contortionist at my age to change that one. Re-aligned the shaft. More background: the last couple of times out the engine idle was a little rough and when in gear would drop down to 5-600 rpm but still ran OK.

The problem: after getting everything back together and starting the engine, when he rpms drop below 1000, the engine shakes really bad and seems to surge intermittently. At 1000 and above it smoothes right out. The shake is there with the transmission in neutral. Just gets worse when in gear. With the transmission in gear, the engine is silky smooth above 1000 rpm all the way to 2600 rpm, all the bad vibrations in certain rpm ranges are gone and this with only the front 2 mounts changed.

I can't figure out how changing the front mounts could have caused the engine to shake like it does at low rpms. If it did, anyone have any recommendations on the fix? Could having the new mounts in front, the old in the rear be the problem?

Also, the engine manual doesn't list an idle speed rpm. It idles normally at about 800. Is this about normal for the M35A? The manual says to not mess with the throttle linkage stops under penalty of death. Anyone know how to adjust the idle without moving the idle stop set screw? Although 1000 rpm is a bit fast I think.

Hope this makes sense, as I am a bit confused about the whole situation at the moment. Any suggestions appreciated.

Also, has anyone considered cutting out an access "door" in the rear birth so you can align the shaft, access the heat exchanger, etc. if your not a 13 year old gymnast? It is my understanding the Mark IIs has one?

Jack Mansfield, C34 # 1169 High Cotton II, Port Arkansas, TX, randy@iycharter.com

WOW! I had the same results with the vibration at slow speed after changing my mount last week. Here is a note I sent to Ron Hill and his reply. Hope it helps.

Capt Al, alwsail@aol.com "Kindred Spirit" #55

Ron

I did my engine mount switch over the weekend and then motored 9 hrs total the next three days. Yes, it is quieter but when I stopped after the first day the low idle would shake the engine where I thought it was going to rattle out of the boat. Sped it up to 900 rpm, where it should be anyway and it goes away. So I went below on a fellow C30’s boat and tried shaking his engine and it would NOT MOVE at all. Went back to mine with the new mounts and I can shake it all over the place! If it shacks side to side will it not shack front to rear? It does show how it keeps the vibration reaching the boat but they seem very soft to me! It is much quieter when running and I have tried twice to align the shaft with some success, but it seems hard as the feet need to be preloaded and as I adjust one it throws off another. I do have to remove one (someday) and make the slots wide for more sideways movement. All in all I like them but being able to shake the engine by hand bothers me a little.

Any comments? I will send to the list, C30 and Catalina...I don't have time for the C34 board.

Thanks for any comments

Capt Al, alwsail@aol.com "Kindred Spirit" #55

RONS REPLY:

Al : Let me see if I can adequately answer you questions on the Vetus K50 mounts. Vibration . I learned in a Diesel Mechanics Course that a diesel engine inherently vibrates side to side. I placed an indelible mark on the drive shaft just forward of the packing gland nut and I haven't seen the mark move or signs of rubbing out. At haul out I saw no shinny spots on either side of the drive shaft at the cutlass bearing. So I don't think the shaft is moving any distance fore and aft - to speak of. When I asked what RPM the diesel should idle at the answer was, "just above where it doesn't shake your teeth out!" The course also demonstrated that at a higher rpm than idle, an engine (less the gyroscopic precession from the "spinning of the flywheel") would sit in one place while running! If you think about it, everything inside an engine is highly machined & must be well balanced or the seals would go and it would self-destruct from the inside. I've found that my high output alternator will not really start putting out amps until you hit 1300 -1500 rpm. Also, when it's putting out 60+amps the side load is about 3hp drag down, so you need to keep the rpm above a low idle. My engine shakes at 800rpm, but I don't idle the engine much below 1200 anyway, because at low idle is where the engine also loads up and carbon accumulates in the top of the cylinders. Going into a slip I'll go into lower idle (9-1000), but the shifter will be in neutral and not for too long. Shifting at a low rpm is hard on the engine (Especially with boat moving forward when going into reverse) and shifting at 1500rpm & up is hard on the transmission.

Alignment. I was able to get mine within .001" and did recheck it a couple of times. I did not run the engine in-between, because I didn't think of doing it. I just wanted to make sure it was correct before I took off the hard coupling and reinstalled my flexible coupling. That was a little bit of a pain to do.

Have to admit I've never tried to shake my engine. I did ask Vetus what the life of the mounts were and the reply was, "if the engine is properly aligned, the mounts will last the life of the engine." The problem with our Universal engines is the location of the oil filter above the FWD port mount and the Oberdorfer/Sherwood weep hole just above the FWD starboard mount. If you happen to have an oil leak in the engine side of the raw water pump or spill some oil changing filters, that oil will KILL the rubber in any mount.

Think I may go the boat tomorrow and I'll try to shake my engine. Since installing the new K50's I think I've put on 4-500 hrs (1-1/2 seasons). Having motored a total of 3500hrs +, you couldn't give me the old style mounts back for free - Installed!!

Hope I've made some sense. Let me know if I've cleared things up.

Ron Hill

Jack

I was able to reach the front mounting bolts of the REAR mounts from the front of the engine. Then I crawled into that hole in the aft cabin and removed the back bolt and the foot from the engine. Just a comment to help if you want. I found that if I put the metal cover part of the new foot in a vice that I could undo the lock nut that holds the foot threaded shaft and remove the shaft. I now had a foot with no threaded post. Now you can put the foot base on first and pass the threaded post down thru the engine and screw it in with the appropriate nuts and washers and never have to lift the engine. So you ask how did I get the

old ones out without raising the engine? I used my saw zal with a metal cutting blade and cut the shaft right above the old foot base. Before I started I measured the height of each corner of the engine. Then I started with the front right and cut out the old and put in the new, adjusted its height and then moved on to the next. I only worked up a sweat on one of the rear feet because of working on my head. Sorry if this sounds too easy for those who have do it the other way but the new feet DO come apart. Be very careful when tightening that lock nut on the shaft to base as it will turn the metal cover. Make sure everything is straight before tightening the adjusting nuts to the engine.

All make sense?

Capt Al

Al : Good for you. I hadn't thought of doing it that way - guess I was fixated with raising the engine. The only real important item is to measure the height of each engine bracket, so you could get the nearly correct adjustment height for each new mount. That makes it easier on engine alignment. In fact you wouldn't need to uncouple the drive shaft from the transmission doing it your way! Good show!!

Ron

Capt. Al

Thanks for the response. Apparently this not an uncommon event when changing to softer mounts. Will change out the rear mounts next trip down and see what that does. May just have to idle at 1000 with the new mounts. Having the engine run so smoothly otherwise will be a good tradeoff.

As Ron said, will just have to spend more time in neutral when docking to Keep boat speed down. I didn't have any problems aligning the shaft (other than it's a b&%# to access the coupling). Perhaps the heavier weight of the M35 makes a difference there??

Jack Mansfield, C34 # 1169, Port Aransas, TX

Capt Al,

Just a quick question about why the higher idle. Most of the Yanmar/Universal engine books recommend 8-900 idle to minimize the noise and more importantly the additional wear on the transmission shifting gears. I'm bringing this up to be controversial, but just wondered why the higher idle rpm. I haven't followed this thread, but it seems some are going to different engine mounts than the standard recommended by either the engine manufacturer or Catalina. One of the emails mentioned a 'soft' mount. I have never heard of these! Now I am really curious.

Have a great day.

Randy

Randy

Yes the new Vetus mounts are SOFT. That is the word we gave them, not Vetus! Softer than I would like. But as Ron Hill said and I agree, "you couldn't give me the old style mounts back for free - Installed!!"

With the new mounts, I can put my hand on top of the engine and can shake it back and forth. I tried this before I changed them and the engine would NOT move.

SO WHY THE HIGHER IDLE???? Because the engine shakes at 7-800rpm with the new mounts. The shifting seems fine at 950 RPM; I do not worry about that. Also you have to be able to hear the engine and at 700 rpm and with the new mounts it’s "quite"......if it does not shake. THE ENGINE IS MUCH QUIETER AT ALL SPEEDS WITH THE NEW MOUNTS!

Capt Al

Randy:

For a bit more background, C34s seem to have an inherent design problem with engine vibrations at certain rpm ranges. In particular all the woodwork around the engine compartment, cockpit locker doors, etc really set up a loud, irritating harmonic vibration. You just dont run in certain RPM ranges (1500-1700 rpms were the worst on my '91). The factory engine mounts are very hard, almost no give. The Vetus are "softer" and absorb the vibrations rather than transferrring them to the stringers. The downside seems to be having to run at a higher idle speed. As Al said, the engine is MUCH quiter at all speeds above 1000 rpm, a very good trade off as far as I am concerned.
Perhaps they have changed things on the Mark IIs ??
Jack Mansfield, C34 # 1169, Port Aransas, TX

Important: The opinions expressed here are those of the individual contributors to this page, and not those of the Catalina 34 International Association or Catalina Yachts, Inc. Additionally, this material has not been reviewed by Catalina Yachts, Inc. for technical accuracy. This page's maintainer cannot guarantee the accuracy of this information or the desirability of suggested modifications or upgrades. Please obtain assistance from a competent marine mechanic or boatyard prior to making any significant modifications to your vessel.