Background: Engine was working when I brought her to this marina in Fall 2022. Good stream coming out exhaust.
Yesterday I changed out the impeller...old one looked good with no pieces missing, supple.
I cleaned the cover plate and removed the old gasket residue, placed on flat surface and lightly sanded with 220grit...same with impeller housing face.
Replaced with new impeller and new gasket.
Opened the sea cock and started the engine...just a trickle of water coming out exhaust...temp never got over 145 after 10min.
Re-checked impeller: some water came out when I removed the face and gasket...back in with impeller and gasket.
Started engine...same issue.
Tried to check sea strainer but I don't have a wrench to fit that clear plastic housing but there was water in the strainer.
Removed hose going to HX...no water coming out.
I've reviewed every article I can find so now my mind is going in six directions.
Where do I go from here?
Also the exhaust blue hump hose seems to be bulged out (ballooned.)
Simple things first- you verified the raw water seacock is fully opened?
Until I can get the sea strainer off I can't say for certain, but there is water in the strainer, and the strainer looks clear. Should I remove the hose and then open the strainer slightly to see?
In your post asking about a wrench, the photo shows the seacock is closed. Did you turn the handle 90 degrees to the open position?
I did, but I closed it when I was trying to remove the strainer.
I always put some dish soap on the impellor when I install it. This gives the pump some lubrocity until the water makes it there and gives me a visual signal that the water has made a complete circuit when soap bubbles appear at the exhaust flow.
Dishsoap was a great idea. I ran to make sure water getting to impeller, then out of impeller. After about thirty seconds, soap bubbles began appearing out exhaust along with good stream of water. Don't know exactly what happened, but maybe pulling the plug helped prime the pump, or there was some debris in the way...or it was the old lady down the dock who was throwing chicken bones and chanting for me.
Anyway...if the answer ain't on this site, it's an unsolvable conundrum. Thanks for everyone's help.
Quote from: Porchhound on August 11, 2023, 10:55:51 AM
Dishsoap was a great idea. I ran to make sure water getting to impeller, then out of impeller. After about thirty seconds, soap bubbles began appearing out exhaust along with good stream of water. Don't know exactly what happened, but maybe pulling the plug helped prime the pump, or there was some debris in the way...or it was the old lady down the dock who was throwing chicken bones and chanting for me.
Anyway...if the answer ain't on this site, it's an unsolvable conundrum. Thanks for everyone's help.
The plug is theoretically in case one needs to prime it. You may have had an airlock and a dry impeller having enough air leakage to not create the vacuum needed to self-prime. Is the pump below the waterline on the 34? On my engine I can crack the pump cover to verify the pump is getting water.
Remember also it's not always all about the strainer - the thru hull can get weeded-up as well.
Remember also, righty-tighty/lefty-loosey (looking of course at the END of the strainer.
You mentioned looking for a diagram? of the cooling? What precisely were you referring to and I can probably point you to it.
Careful Dave - If the answer isn't on the forum - well, we just make one up. :rolling :lol: :shock:
The pump is below the water line. I'm going to have someone dive on the boat for zincs and cleaning. I'll have them inspect the thru hulls while I'm at it. It sat here for nine months. I did double check my righty-tighty maneuver...just in case!
I remember seeing a raw and fresh water cooling chart where corrections had been made on the one in the manual.
Regarding made-up solutions, I'll happily take a tall tale when facts are beyond reach.
Strainer - good idea.
Take off the hose from the thru hull/strainer to the rw pump at the pump, use a dinghy foot pump to BLOW BACK through the hose, will clear out the thru hull (usually); diver should, too. :D Depending on your strainer arrangement you could also do this under the head sink.
After that, SUCK on the hose to get water through it, it's the best way to prove it, because yes even though the pump is below the waterline the tight fit of the pump faceplate does not allow water to flow, even "downhill"; it's a reality, and the HX is uphill, too.
Quote from: Porchhound on August 11, 2023, 11:33:55 AM
I remember seeing a raw and fresh water cooling chart where corrections had been made on the one in the manual.
Dave
I had placed my corrected page in the m-25, et al, 1989 Owners Manual on the wiki site "manuals" page. Unfortunately you have to get to the manuals page via a convoluted path because the link on the main Wiki page is broken and until "someone" will fix it, it remains that way.
Simple fix, but I can't get it fixed for several years.
Thanks...I'll go find it. I knew I saw it somewhere!
Porch : Go to an auto parts store and get your self a strap wrench. You are going to need it to get that strainer apart to eventually clean it out. Be careful because there is a SQUARE "O" ring gasket between the screw-on bowl and the strainer body that attached to the thru hull.!! Then only hand tighten that strainer bowl!!!
The raw water system is simple. The raw water come into the thru hull with the strainer, then it goes around the back of the sink head, then in the top back of the engine to the inlet on your raw water pump (starboard side). Then the water is pumped to the heat exchanger, then out of the HX to a Anti Syphon valve mounted on the top port side of the engine (look for it thru the head sink door). Then it goes from the AS Valve to the nipple on the exhaust riser (mixing with the exhaust gases) into the aqua lift muffler. Then out the muffler to the exhaust mounted in the port side stern (underneath). :shock:
A few thoughts .
Strap wrench worked, very little debris in the filter. I'm thinking I didn't get a prime after I replaced the impeller. Hope that doesn't mean the pump is getting weak, but it runs fine now.
Did you read reply #9? Pumps don't "get weak."
I read it but didn't make that connection. Thanks.
Quote from: Porchhound on August 13, 2023, 07:41:27 AM
I'm thinking I didn't get a prime after I replaced the impeller. Hope that doesn't mean the pump is getting weak, but it runs fine now.
Dave, "weak" - comes down to the impeller not sealing well because either (1) it's worn, (2) the pump body is worn, or (3) a dry impeller.
The pump is self-priming to a point but as I said before even if below the waterline there can be an airlock. What I didn't say in my post is that lubing the impeller does more than keep it from burning up. The lube seals the air leaking past a dry impeller so that it can draw a vacuum. I installed a 2-inch pump that drew only 7 inches of vacuum (8 feet of water.) After the seals were whetted it consistently draws 25 inches vacuum (28 feet of water.) The same thing happens with your little 1/2" pump.
It also might not pump well if the impeller is intact yet worn. It can be supple and the fins make contact with the cam but (depending on how many hours) the impeller faces can be worn and seal poorly. A worn DRY impeller has that much more difficulty drawing a vacuum. I always recommend a new impeller well before it appears necessary -- it's cheap insurance in the big picture of boat costs.
The pump body or cover plate can also be worn (the bronze body is harder than the brass cover but both can wear.) The depth of the pump water cavity is critical -- too much wear and it doesn't matter how good the o-ring or gasket is or how flat the cover is. Wear in the body is like using too thick a gasket or o-ring. The impeller doesn't seal like a new pump.
Use genuine impellers. There was a report by a member who bought an Amazon knockoff and it did not prime -- probably the thickness of the impeller was "off" a bit and sealed poorly against the pump body.
Quote from: Porchhound on August 15, 2023, 10:10:49 AM
I used the stay cool pump kit that was onboard my C34 M25 engine (Oberdorfer pump).
I'm still having problems with my raw water system moving water out the exhaust although it did work again for awhile, one time. Once I shut the engine down and removed the strainer for inspection and cleaning it wouldn't pump water to the impeller the next time I started it.
I have made certain my thru hull, strainer, and inlet hose to pump were clear (yes, Stu I got a mouthful of tasty marina water!) I lubed the impeller and squirted dawn dish soap into the plug hole, but no bueno. I also blew through the hose to the HX and had some resistance, but no blockage. I got a great list of things that may be the problem from KW, but some of those pump and impeller housing issues are difficult to check out without replacing the pump and housing.
The photo is a before I cleaned up the housing cover. I lightly sanded the cover on a flat surface (220 grit) and then used sandpaper to remove the old gasket from the impeller housing frame.
Which leads me to question the impeller/gasket kit I used. I have a second kit also from Stay Cool Pumps.
I don't want to go out until I know exactly what the problem is, and that I can consistently start and run my engine when I need it.
Dave
Draining the strainer and hose may have introduced another airlock that the impeller could not overcome to prime. This is just a guess but if the pump/impeller was wet, possibly the dishsoap was thinned and did not effectively seal the impeller (air leakage not creating a vacuum vs a dry pump.) Who knows??
(1) I REPEAT
DO NOT use any but genuine impellers
AND GASKETS/O-RINGS by the pump manufacturer, whether Oberdorfer or Sherwood. (Stay Cool is one knockoff that has been a problem.)
(2) It can be dangerous (seriously, I mean it) to take at face value that a PO had followed good or accepted practice, or knew any more, or has done anything better than you can to maintain a boat or its systems!!!
Sanding the face of the pump body (depending of course on how aggressively) will alter the depth of the water chamber and alter how the impeller seals and can increase subsequent wear on the chamber and cover (
so can using a non-OEM gasket.) Avoid sanding that unless absolutely necessary -- apply SuperLube Gel (ptfe) to help keep the gasket from seizing. IMO SLG vs dishsoap is a better lube because it's not water-soluble and so will hang out a bit longer on the back of the water chamber. There's a cover available that uses an o-ring (like the current "
Ob N202" pumps) instead of the paper gasket.
Also SLG the impeller hub/shaft to help prevent the impeller hub from seizing (especially in salt) on the flat If you pull the shaft to R&R the impeller (some say it's easier ) then SLG the tip of the shaft so it slides past w/o knicking the two rubber lip seals.
If your setup is such that you can "rod" the valve/thru hull to assure that you have nothing blocking it that's an option. It's simple to set up that configuration on our 30s so that it's easy to "rod" it but admittedly I don't know about on the 34.
PS: Remove and deep-six the C-clip that holds the impeller onto the shaft -- don't use it when you replace w/ a new Ob impeller. The Wiki engine cooling section tells why.
-Ken
Porch : How was the gasket (the square "O" ring) that fits in the strainer bowl. It just might be the source of your "air leak" !!
A thought
The mechanic inspected the O-ring gasket and said it looked fine. I was a little shy in hand tightening the strainer, he thought, so he went a 1/4 turn past that. Because it lies perpendicular to the thru hull plumbing, an air bubble seems to never go away.
As of this writing, the exhaust flow looks good and the engine temp is staying at around 145 (checked with a FLIR gun). I took a 7sec video of the flow at 1200RPM but I don't know if videos can be posted on here. Some sites prohibit them.
Quote from: Porchhound on August 16, 2023, 04:09:28 PM
The mechanic inspected the O-ring gasket and said it looked fine. I was a little shy in hand tightening the strainer, he thought, so he went a 1/4 turn past that. Because it lies perpendicular to the thru hull plumbing, an air bubble seems to never go away.
As of this writing, the exhaust flow looks good and the engine temp is staying at around 145 (checked with a FLIR gun). I took a 7sec video of the flow at 1200RPM but I don't know if videos can be posted on here. Some sites prohibit them.
OK question where are you? Cold seawater?
Does she have a thermostat installed? 145 is too low -- and unlikely w/ a working 160 TStat and a 2" Hx.
1200 rpm will get you nowhere. You need to get to cruising rpm for at least 5 minutes. My temp gets up to 180 (with a 180 thermostat) only after i've left the slip and am moving away.
Cold seawater. I didn't check the thermostat. The surveyor noted 155deg at the thermostat housing, and that was late last October. I just replaced the battery on my heat gun so I'll take a reading in the AM.
We're taking her out tomorrow (fingers crossed) so I'll be able to get a realistic read on her. I discovered a bad ground for the Temp gauge and RPM. I should get more precise readings now.
Good water flow this AM. My temp gauge died about twenty min out of the marina but FLIR directed at thermostat housing indicated 188 deg after we'd been motoring for about thirty min and stayed at that temp.
On a buoy now trying to find out the electrical issue with the temp gauge. I also noticed, upon pulling the cockpit control panel, a hot spot on my tach.
Porch : Look at the wire attachment to the sender on the thermostat - on the engine!! It's more apt to be "off" rather than at the instrument!!
A thought
I checked the connection and it seems to be tight. For some reason the PO ran a ground wire from the engine to the body of the sensors and attached it with a hose clamp, which makes no sense to me in that the sensor threads into the block directly. Any guesses why the tach has that hot spot?
It was working yesterday perfectly and was installed in 2019. The ground wire is a mystery to me.
The hotspot is from the incandescent light bulb originally installed by the factory to light up the gauge. Some of us have replaced the incandescent bulbs with LED bulbs.
Dave
The TStat bond that I supply with new harnesses.
Think about -
What's behind the burn spot?
Why does it make sense to separately bond the TStat cap?
The gauge troubleshooting guide is on the Wiki and the steps will determine if the gauge or the wiring is faulty (the temp gauge steps have also been discussed on here and are in the archives.)
While anchored I took the spare time and cleaned more on the intake system of the HX. I thought I had done a good job but more scale came out, and the engine ran cooler (170F vs 185-190). I'm letting lime away soak in there now via the inlet hose. I hope it doesn't eat my hose! The 2inch HX only has one end that opens, making cleaning more difficult. I guess a radiator shop will be the best bet.
I disconnected the ground on the heat sensor (it's just the bare end of a wire) and repositioned it for more contact. The gauge began working again, but it still reads about ten deg higher than the FLIR. Of course the sensor is having direct contact with the coolant. I'm going to borrow from your photo KW and add an end to that ground cable the clamp can grab.
As always, thanks for all the help!
ABA #17 stainless Mini Clamp.
So? Haven't answered why it's a good idea to bond the Tstst separately?
(and why just bonding it back to a nut on the water flange is not the best way)
As the troubleshooting guide says, Temp readings are +/- 15%
From what I'm reading, bonding directly results in an accurate ambient Ohm reading to the sensor, thus accurate readings as the temps go up. I'm still reading about this system. I never really knew how resistance temp detectors worked.
You have a Tstat cap that sits on top of a Tstat and gasket, therefore doesn't directly contact the Water Flange underneath.
The water flange has a gasket so doesn't contact the engine block.
The bolts that hold both those are subject to corrosion. Looking at the pic of your cap it's obvious that the bolts aren't making a good, clean bond and who knows what corrosion is on the threads. My Tstat cap bolts were so corroded in that I had to drill them out and buy a new cap.
The proper place to bond the Tstat cap is to a known good ground, not to a water flange bolt head. It's probably irrelevant because my guess is that your engine block and panel probably are not properly grounded (unless PO did the mods needed to do that.) So the bandaid bond of the TStat and messing with the temp gauge wiring is just that, bandaids until you "get into" bringing the 'lectrical up to snuff. 12v stuff like the panel will work but with the temp gauge (and fuel level) the senders AND gauges all need to be grounded properly to read accurately.
It never ends on a boat!! If/when you want to tackle a 'lectrical upgrade we can walk you thru that.
Quote from: Porchhound on August 18, 2023, 12:27:39 PM
While anchored I took the spare time and cleaned more on the intake system of the HX. I thought I had done a good job but more scale came out, and the engine ran cooler (170F vs 185-190). I'm letting lime away soak in there now via the inlet hose. I hope it doesn't eat my hose! The 2inch HX only has one end that opens, making cleaning more difficult. I guess a radiator shop will be the best bet.
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I had a 2" HX on my M25 when I bought my boat in 1998. The PO told us the engine overheated if pushed to WOT for extended periods. He said "it was normal." He also gave me ALL of the back issues of Mainsheet magazine back to 1987 when tech articles began to appear that included the C34 (although the M25 engine appeared in C30s and C36s back then, too). So I read all those back issues, and as some of the sticky topics explain, on Xmas Day 1998 I started the Tech Notes Index and the Association built the Tech Notes Online from that. Included in that effort was a lot of information about those old smaller HXs. I finally took mine off the engine completely. And when I shook it it sounded like a mariachi band!:D Lots of pieces of zinc fell out when I removed the single end cap. But the REAL CULPRIT for the overheating was the buildup of salt on the inlet port. This is where the salt deposits itself from the cold rw from the rw pump when it hits the hot HX. Once I cleared that blockage out (more than half of the port was blocked) the engine ran cool even at WOT. Years later I got the boat bucks together for a 3" HX. You really need to remove it from the engine to clean it. I don't believe a radiator shop is necessary. Lots of folks talk about the tubes needing to be cleaned, but as a mechanical engineer, I note that the tubes is where the water moves the fastest and the tubes should be just fine. It's the floating pieces of zinc, impeller pieces and salt in the inlet port that are the real issues.
The point is that what the tech notes since 1987 say is true: the 2" HX is marginal but OK for that engine if it is free and clean. The M25XP engine is two more HP and it includes a 3" HX and the corrected alternator bracket. I did both to my M25.
I sure hope you've done the alternator bracket.
I looked at the panel connections and it looks like an upgrade is in order. Somehow in the process of screwing around I removed the connector to my oil sending unit. It seemed loose so I crimped the female end of the bayonet connector and reattached, but in the process lost my alarm. I'm going to look for a fuse in that line.
According to the PO (who did several of the upgrades suggested on here) he replaced the "new wiring harness for the engine." The temp sensor gauge is new, as is the amp meter. There's obviously more to do in several areas, but that's okay. That's the only way to really learn a boat and its systems. Thanks for the offer. I'll take you up on that.
Stu, the alternator bracket upgrade was one of the first things I looked for during my initial walk-thru, thanks to all the tech notes and the list of "must-do's." The PO made that upgrade as soon as he purchased the boat several years ago. When we are back in the marina I plan on removing the HX and giving it a good cleaning, probably do a better job with the lime away with it off.
Porch : If you still have an ammeter the PO did NOT do the wiring harness upgrade!!! The main part of the wiring harness upgrade was to REPLACE the ammeter with a Voltmeter and take the alternator output and run it to the starter solenoid stud!! There also was a wiring block that all of the wires connected into and the trailer connectors were cut out!! Best you check your M25 wiring!!
A few thoughts
I misspoke, Ron. It is a voltmeter...kinda dates me I guess, but I will check the wiring.