Low RPM and sudden loss of power

[stgermain45]

Yesterday when taking our 1987 E28 out, the engine would not rise above 2200 RPM. She is normally capable of well over 3000 RPM with the manual quoting 3600, though I'll never test it. I typically don't ever force her above 2600 RPM, which is at the low end of the manual's cruising recommendations. It is a Universal M12 10HP diesel engine with about 225 hours on it. As an experiment, I forced the arm to full throttle, but there was no increase above 2200 RPM (not just a meter rating - no power increase while giving more throttle). Also, a slight backing off of the throttle produced a rapid drop in RPM and considerable loss in power. I can't speak yet as to whether these symptoms occurred in neutral as well, but will check when I'm down at the boat next.

I found this related thread and plan to look into some of the advice offered:
http://www.ericsonyachts.org/infoexchange/showthread.php?t=2523

Can anyone think of other possible things to look into? The diver was at the boat just a few days ago, so I'm doubtful about debris on the prop, but haven't yet stuck my head underwater.

I changed the fuel filters recently but have taken the boat out under power since then without any issues. Other than pulling the dipstick to check oil, I haven't touched the engine since successfully motoring about a week and a half ago. One additional thing I noticed was that the throttle is also pretty tough to throttle up/down and requires considerably more arm strength than would normally be comfortable - it seems to have progressively gotten worse since purchasing the boat in August.

I should probably also note that we redid the entire wet exhaust system due to a cracked riser several months back and with all new hoses (including coolant hoses and a brand new hot water heater, given the opportunity of access). However, we've motored without any problems probably 20 times since. And there was nothing unusual about the amount of water out of the transom thru hull yesterday.

Air filter has been recently replaced a few months back as well.

Any ideas?

Thanks,
Chris

 

[Loren Beach]

Air Leak, Maybe

My vote, based only my own experience, is for a miniscule air leak around one of the two gaskets in the Racor filter. Or, maybe in the plastic plug or plunger in the top...
Since you recently changed out the filters, there's always a chance of this happening.


While we never really found the exact leak point when our engine went thru the very same running problem (and then later that day refused to restart) a few years ago, the Racor was nonetheless determined to be the culprit.

Our trouble shooting routine was to check the lines from the tank for gunk plug ups -- there were none, and finally bypass the Racor and then depend on the Universal spin-on filter for the rest of our vacation. Worked fine then.
When back to home dock I changed out the outdated model Racor for a new one, and replaced all the ancient fuel lines.

Loren

 

[rwthomas1]

You mention that the throttle lever is stiff and getting worse. Are you sure that the cable is actually pushing the lever on the IP to full power? It could be as simple as the cable not doing its job anymore? Also sounds like fuel starvation, from a leak at the Racor or some other restriction. I'm betting on the cable though....

RT

 

[stgermain45]

Nope, not sure of anything! Thanks for the great suggestions. I'm pretty sure the throttle lever has gotten worse..at least I don't remember it being as stiff as it has been lately. If it is the root of the problem, would it really cause a dramatic loss in power when easing off only slightly?

The throttle lever in itself has always been one of those idiosyncratic things on the boat. When at low throttle with the lever aft, it gets in the way of the steering wheel and I need to remove the ball off the top to provide (barely enough) clearance. Since acquiring the boat, I've always wanted to rotate it's range of travel forward. Anyone ever have the need to do something like this?

I'll look at the possibility of a bad cable or an air leak next time I'm down at the boat.

I did not have to bleed at the injectors when changing both the primary and secondary filters. The M12 has continuous self bleeding and the engine started right up and ran great after simply filling the new filters with diesel and slapping them on. But a leak at the Racor gaskets, that's something I didn't ponder! Somewhere in the back of my head, I thought, "it couldn't be this easy!"

Thanks,
Chris

 

[Frank Langer]

Chris, I replaced the throttle cable on our boat last year and it was easier than I anticipated. One way that I can tell if the cable is working properly is move the lever on the engine by hand while watching the pedestal throttle lever. If you can move it easily at the engine and it moves at the pedestal by the same amount, then probably the cable is doing it's job. Also check whether it moves through the full range. I agree with Rob that this is where I guess your problem is. If you need to replace it, you can undo it at both ends, look at the writing on the existing cable to see what length it is to purchase a new one. However, I looked carefully at the existing route and decided to run the new cable a bit differently to minimize curves; then I had to measure the new route with a tape measure to determine what size (by number of feet) I needed. Some people suggest you tie a messenger line to one end before you pull out the old one so you can thread the new one. I didn't do that, and found that I could thread the cable easily down the pedestal and then pull it to where it attaches on the engine. Then you need to make the required adjustment so that full lever movement at the pedestal also gives you full throttle control at the engine, but you can get more information about that if you get to that point.

Frank

 

[stgermain45]

Thanks for the tips, Frank! I'll check it out.

 

[stgermain45]

I tracked down my problem. The throttle lever had become misaligned from needing to put excess force on the lever over time. A little WD-40 at the inside of the pedestal and also at the engine lever really helped for smoother travel of the throttle lever. I realigned the lever by forcefully shifting the arm while holding the connecting inside lever in place (inside the pedestal housing where the cable attaches). The cable was functioning fine afterward and I'm now able to get full power when motoring. I am happy it is functioning OK now, but I'm thinking that this will happen again over time. I'd imagine it shouldn't be allowed to slip like I described above.

 

[mherrcat]

WD-40 is not particularly great as a lubricant. Yes, it works good at first but it doesn't last; over time it dries out and gums up.