Vibration in Neutral Need Advice

[RV61]

This past weekend after splashing down a couple weeks ago went motoring out to the lake and found that in mid range of RPMs I had a much loud rattleing vibration noise. Cranked up the motor higher no rattling same in idle. Back at the dock I decided to look around while the engine was in nuetral thought something may be loose or something in the lockers rattling. Took everything out still loud rattling vibration in mid range RPM. Could not find anthing astray. This vibration rattle is loud like someone slapping or hammering the hull with metal. Searched our site and came up with motor mounts could be this issue as I believe they are original. When inspecting them what does one need to look for to tell if they are servicable or need replaced??  I put in new SS shaft, Cutlass bearing and coupler two years ago and had aligned and ruled all that out becuase the noise is there when in nuetral. I will make sure the mounts  are tight next week when I go. Any advise on inspecting, adjusting etc. on the motor mounts would be greatly appreciated by this mechanically challanged but yet learning sailor. I will also make sure the heat exhager is not banging against any glass Anything else to look for or tighted down to eliminate this hidious noise??
Thanks agian     
   

[Terry Forshier]

I was told last year by the boat yard foreman where I go that if the motor vibrates at strart up and low or idle speed then you need new motor mounts. You should be able to see this if you start the motor and watch . As the motor reves up it will settle down and you will get less vibration. Mounts on my old YANMAR were adjustable by thightening the nuts on them One above and one below the lip. ( I just bought my C34 and have not checked this out on the Universal.) hope this helps. Terry

[David Sanner]

Mid-Range of RPMs?  I'm assuming you have a M25(__) which has rough/unbalanced
motion when you are running somewhere between 1600 & 1900 RPMs.

It could be that your engine is not running as well as it should which is exaggerating
the balance problem (partially plugged injector, dirty fuel/filter, stuck ring, etc...)

And/Or it could be a loose motor mounts but would think you would have the same problem at idle.
Check/tighten them either way.  If you have the K50 or K75 mount they will knock
hard if they bottom out.  They have a semi-rectangular gold cap that covers a rubber
mount with a black base. The original ones on my boat were all silver except a round rubber
bushing between the mounting stud and the base.

Is the motor noticeably moving/shaking at one RPM or another?  My motor noticeably moves
at idle and around 1750 rpm though the higher RPM is harder to see.  You can see/feel it
by looking/holding the engine or around the hump hose between the exhaust pipe and the muffler.

Sounds like either something is hitting something or you've got a loose motor mount.
Also check the screws on your muffler, they could be loose and the muffler could
be hopping around a bit.  And maybe check your alignment if all else fails... if a mount
is broken or out of adjustment it might show up there as well. 

As far as checking the mounts themselves take a look when you tighten them and make
sure the metal or rubber is not cracked.  If the rubber in the mount is broken you might
be able to see this when the motor is running... maybe.

Good Luck.

[Ron Hill]

Rick : Looking at you hull # I assume that you have an M25 (21hp) engine. 
Have your engine mounts or your injectors EVER been changed??  If they haven't I'd recommend doing both.  Then align the engine/shaft and you should be in good shape. 
I'm the guy that wrote the first article on changing engine mounts.  Selected the Vetus K50 which is a nice mount.  Then changed the rear mounts to the K75 which seem to work perfectly.  Still waiting for all of those other engine mount articles by other manufactures that I've have never seen surface!!  I selected Vetus as the mounting holes were the same, engine/xmission weight & torque was OK and the mount was "vertically" compatible. 
Try them you'll like them.   Ron

[Earl Miller]

I had a similar loud banging noise .... it turned out to be a loose zinc on the propeller shaft.  It had settled against the strut and was hitting the cutlass bearing housing.  May be worth checking.

[RV61]

Yes it is the Universal M-25. I have had the boat only the past three years and based on the lack of maintenance and condition when purchased I need to assume that the mounts and injectors are original. I will have a chance to inspect engine movement at different RPMs this weekend. Will check each of the mounts for tightness and rubber also the make sure muffler is secure and not bumping something. What is the proper torque on the mounts?? I changed all the fuel filter approx 10 hours previous and drained a little fuel from the separator this  weekend and appeared to clean amber pink. No noticeable black or white exhaust as I looked as part my spring checklist. How does one check an injector? just crack it open until some fuel come out and if the motor settles down you know there is an issue? If partially clogged is that something this mechanically  challenged sailor can clean or should I spend the $$ and replace all three?? Thanks again for all the support it sure has been challenging but yet rewarding putting this fine boat back together again.       
Rick

[Ken Juul]

On the advice of a marine diesel mech, verified by the help desk at Chevron,  I cleaned the engine side fuel system/injectors with a bottle of "Techron" poured in a gallon of fuel.   Rigged a temp line from the electric fuel pump to the gallon container and ran the engine at 1500 in neutral until most of the fuel was gone.  I was careful not to run out of fuel to avoid getting excess air into the system.  Smoke changed colors a couple of times during the cleaning so it was doing something.  Engine seems to run smoother and smokes less under load since the cleaning.

[SteveLyle]

Rick,

I assume from your note that the mid-range vibration is new - not something you've noticed before.

I expect that Ron was trying to cover the most likely causes of engine vibration, which are typically alignment, mounts, and injectors.  Ron's more qualified than I, but I would expect that injector-based vibration would be across the rpm range, not in a band.  New or rebuilt injectors, or new mounts, might be a good thing to do, but it doesn't sound like the root of your problem.

Mounts don't actually stop engine virbration at all, they just pass less of the vibration to the hull, so the engine sounds quieter.  In fact, the Vetus mounts let the engine move around more than the stock mounts, so if there is something inherently wrong with the engine (e.g., a bad injector or two), you'll notice it more with new mounts, in terms of engine movement, than you would have with the old mounts.

When you run at the mid-range in neutral at the dock, what does it look like the engine is doing - hopping around, or sitting still?  It should be sitting still.  If it is, it's likely that the source of the vibration isn't new at all, what's new is the effect - i.e., something else is loose/banging around that has a natural frequency in the mid-range RPM of the engine.  I'd focus on figuring out what that is (i.e., what's banging), fix it, then assess mounts/injectors/alignment.

Steve

[RV61]

Thanks for all the replies. I found the source of the banging and cause of some of the vibration. Two of the motor mounts were they bolt to the stringers were a little loose. Tightend them down and the banging was reduced to a very narrow range in RPM both in gear and out of gear. The source of the banging is come from the collar around the bellow of the PYI PSS dripless system and the slight vibration from the shaft. When out of gear I went back a slightly pulled up on the shaft and noise went away and same with slightly moving the bellow collar no banging. know I need to figure out how to have this stay aligned.
The engine probably needs to be aligned again anyway so hopefully that will rid of the problem.

[Gary Ambrose]

Rick, another place to check as we had a similar banging problem is the link between shaft and transmission.  We thought thought the noise was loose mounts and alignment.  We have a transmission saver between the shaft and transmission so the problem was hidden.  After disconnecting the shaft from the saver we found that two of four bolts on the transmission flange side were broken.  It is a clover leaf pattern and two were broken on the same side allowing the shaft to turn out of line.  The bad news is that the flange on the transmission does not come off but is turned as a part of the transmission shaft.  That meant a new transmission.  The good news is that the new flange is much heavier and will take more stress.  Ours is an 86 so I imagine newer boats have the more rugged transmission flange.

[Gary Ambrose]

As an add on to the previous post.  Your problem in neutral would not indicate what I am describing since the shaft would be disengaged.  This may help others, however. with vibration at start up an specific RPM's underway.

[Ken Heyman]

Gary & all,

re: "-----Rick, another place to check as we had a similar banging problem is the link between shaft and transmission-----"

I have a chronic "rattle" at low RPM (maybe up to 1100) and then it goes away when the throttle is advanced. Turning the rudder sharply at low RPM while underway seems to exacerbate the problem. I have learned to live with it as it has stood the test of time but I know it is not right. Are we talking about a rattle or banging. I may check the bolts referred to although I'm convinced that my problem may be the shaft slapping against the hull at it's exit due to an alignment issue.

Thanks,

Ken

[Gary]

Ken,

The rapping sound at low rpm suggests the shaft making contact with the shaft log, that is, the fiberglass tube where the shaft passes through the hull.  It could be that the motor mounts could have shifted a bit.  However, the symptom you describe is what we had with the broken transmission flange.  Two ears on the same side sheared.  It took removing the bolts to find this out.  I think you could loosen the bolts without taking them all the way out to discover if any part of the transmission flange has broken.  The great thing about this board is the shared information.  The bad thing is that we all get very anxious about these problems, especially at the start of a new season or large expense.  I wish you the best and would like to hear how it turns out for you.

Good luck!

Gary

PS:  I have had some login problems so my user name etc may appear as a new register.

[Ron Hill]

Guys : Unless you've(or previous owner) taken extraordinary measures I'll guess that your port forward engine mount is SHOT because of oil on it from changing the oil filter!!  I wrote a Mainsheet article on protecting that mount when you change the filter.
Your starboard fwd mount could also be soft from a leak of oil from the raw water pump. (one lip seal keeps the oil in the engine and the other keeps the water in the pump).
Any coolant (Preston 50% mix) that may have leaked on the rear mounts may also have softened those mounts.

After 10 years of little engine operation and idling you can count on the injectors being carboned up!!!

Bottom line is that you need to change some of the items on your engine, especially consider the hoses that are painted the same color as the 15 year old+ engine!!!!!!!!!!!!! 

Treat your engine to some new mounts and new/rebuilt injectors.  After all you're a YACHT owner and can afford it!!   

[RV61]

 
Guys,
Problem solved banging noise gone I had the boat deisel  mechanic out and he made slight aliagnment adjustment. Banging gone. Needed to lift up slightly. It is now within tollerance . It was worth it to be there to learn how to aliagn for next time.
The injectors are ok and the mounts are ok for now however per Ron's  post and the mechanics discusssion to quiet it down even more I could replace mounts and  injectors. I am going to add that to the list and do the fuel tank clean or replace prior to the new injectors.

I did replace ALL of the hoses over the past couple years but camaccross the engine water intake hose was chaffing on the glass aft  of the engine and almost cut thru the hose as one of the plastic ties came loose.
I fixed that as well as put 4 layers of duct tape on the edge of the glass until i find a more suitable replacement to finnish that edge in case something ends up there again. Lesson learned here is inspect hoses anytime you look in the compartment and carry spare hose just in case.

Thanks again for all the replies and support!!
Rick Vierow