Hello,
Westerbeke 21A
Engine with all filters (2-fuel), fluids (transmission and engine) recently done.
New impellor just done.
No smoke, good exhaust water.
What happens:
Engine starts on first attempt.
Engine purrs from 500 to 3000 rpms, can go up and down without a problem.
Temperature gauge reads about 140.
Once shift is in forward, the boat advances.
Within 1 or 2 minutes, the rpms creep down from 2000 toward 1000 and below with no throttle adjustments. Increasing the throttle has minimal to effect.
The engine will conk out it I didn’t put throttle in neutral and restore rpms to 1500 to 2000.
Once rpms are restored, I drop rpms down and I can put it in gear again.
It will limp along at 2000 rpms, seeming to make an effort, wanting to stall out, and increased throttle has no effect.
Thanks in advance.
Any thoughts?
Richard Templeton
Swell #230 26 Ultra
Annapolis
140 seems a low temperature. Is that the max it gets to? If not, what is it when acting up?
Have you checked for something around the prop/shaft?
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Richard,
Have you checked to see if the fuel tank vent line is clear and not clogged with spider debris? Your symptoms sound consistent with a fuel pump that is able to draw fuel in the beginning, but the longer it runs with a clogged vent line the tank will form a vacuum, and the fuel pump will not be able to pump the fuel. Anyway, something that’s easy to check and cheaper than replacing the fuel pump. I don’t know about the temperature other than to ask are you sure the right thermostat is in the engine?
Jim Cosgrove
FATE 30U #343
Galesville MD
rompinronnie
(Ron Schryver "Alpha Waves" 1987 NS30U Georgian Bay Midland ON)
7
Hi Richard, we’ve had a similar issue and it turned out to be a very dirty filter in the Racor water separator. The engine would run for 1/2 hour or so and then the revs would die. After a short period at idle the fuel pump was able to push some fuel through the dirty filter but not enough for continuous operation. Once that filter was changed all went back to normal. An easy way to determine if this is the issue is to just remove the filter in the Racor unit and try the engine again. The other filters on the engine will suffice for this test.
Another possibility is that there’s a screen on your fuel pick up hose and this may be blocked.
Good luck…Ron
Ron & Diane Schryver
“Alpha Waves” 1987 NS30U #393
Georgian Bay Midland ON
Don, Don, Brian, Frances, Jim and Ron!
Thanks for all the input!
I am pulling boat to paint the bottom and will inspect prop, and will check on all the other suggestions.
Will tether test the boat in the slip, and maybe get a mechanic involved.
Richard
As per Jim Cosgrove’s theory, also check the fuel vent itself on the hull. The screens get corroded and clogged by the corrosion, which can also cause the vacuum pressure preventing fuel flow.
Bob Gehrman
NS30U #396 “Quickbeam”
Baltimore, Maryland
When it starts to loose power open the filler cap. If it recovers it is a tank vent problem. If not I would check the screen in the bottom of the lift pump. They made paper strainers for a little while till they found they would collapse and cut off fuel supply under suction.
Sounds like fuel starvation. Air in the lines would cause it not to run at all. As mentioned the vent, filters and pick up tube are the easy things to check. In that order
The pick up could be obstructed with debris. Mine was too close to the bottom and needed to be shorted to 1/2 inch off the bottom. I had a vent obstructed by spiders, removing the fuel fill proved that was the cause.
Is the lift pump ticking? That would be the next item.
If this does not solve the issue then it is possible you have a small air leak. Any presence of fuel at a connector is a sign you need a strong light to detect these leaks.
One trick to locate the source is start the engine to idle and in order, use electric tape to seal each connection increasing the throttle each time… if the the engine stalls tape the next one… when the stall stops happening you have your leak.
If you changed the 2 filters on the engine you will need to tape test those connections as well. Electrical tape works
There is a small chance it is the high pressure pump but that requires a mechanic skilled in dealing with these pumps.
Bob, Joe, Peter, Debbie, John and all previous persons. Thanks for all the input.
Fuel vent and cap off make no difference.
Made an in-slip tethered trial and degrading in gear is the same.
It just migrates from say 3000 to the point of stalling unless put in neutral and rpms can be increased smoothly to 3000.
Temperature about 160 as usual. Transmission and pro seem normal,
Pulling boat week next to paint and will inspect.
Will have a mechanic address the problem and take your suggestions to heart.
Richard
