Power Loss - Westerbeke 30B Three

[sailor3333]

The first issue was a deceleration stumble problem to near stall, when coming from high rpm to idle. Being fairly easy to do, the injection pump and injectors were sent out for testing and service, and were rebuilt. That didn't solve the problem. It turned out to be a weak governor spring. It was the idle set spring. It sets the throttle (IP rack) linkage to idle rpm when throttle is in neutral and when engine is not running.

Now there's a NEW PROBLEM that didn't exist before the IP and injectors were rebuilt. The engine fails to achieve WOT 3600 rpm under load as it always did before. Now it's like 2800 rpm, a 22% loss in power. As with the previous problem, everything we could think of was done to rule out various other causes before pulling the IP and taking it back to the rebuilder for retesting on his IP machine. It checks out as delivering fuel volume per spec. The IP is a Denso PFR3 #094500-4510 11S. Per rebuilder the replacement Elements used are Denso# 36 090150-4280

Seems to me that the IP is not delivering enough fuel at WOT -- engine seems fuel starved under load. The IP rack moves to its max throw -- my mechanic disconnected linkage rod to governor and operated the rack by hand for load testing. Also, a test was done with fresh fuel in jug piped directly to IP (using a external small lift pump and inline filter) and a new return line back to the jug -- thus, my boat's fuel system was totally eliminated. The boat bottom is clean and the visible saildrive prop is in excellent condition.

The engine has 700 hours. It starts easily and runs fine. There's no smoke of any kind and no oil sheen on water by the exhaust. Oil pressure and engine temperature are normal. There's no air filter (only a visible screen) and no air cut off.

I'm a a dead end here. Any ideas would be much appreciated.

[Nefrut]

Hi Sailor3333, I have a beneteau 331 westerbeke 30b3 with exactly the same original symptoms as you (stumbling after decel, rough idle with low rpm only after warm up).

Could you help me out and let me know the part number of the culprit spring? Looks like the only one possible to replace by just removing the governor cover is part 037048 - "governor propulsion" spring. Is this the one you are describing?

Attaching westerbeke 30b parts manual for reference (governor is on page 22).

https://www.westerbeke.com/parts%20m...parts_list.pdf

[Shelter]

Have you checked exhaust elbow/passages are clear?

[Nefrut]

The theory being that as the engine warms the exhaust gases expand, and if the passage is partly clogged this could cause the engine to stumble at idle? That's a good suggestion, I will check.
thanks

[JoeDoc]

Hey Nefrut, I too have a Beneteau 331 with a Westerbeke 30b3. I'm experiencing the exact same symptoms as you and the OP. Curious to know if checking/clearing the exhaust elbow/passages helped? I will be checking this on my next visit to the boat. Thanks.

Originally Posted by Nefrut

The theory being that as the engine warms the exhaust gases expand, and if the passage is partly clogged this could cause the engine to stumble at idle? That's a good suggestion, I will check.
thanks

[GordMay]

Greetings and welcome aboard the CF, Nefrut.

FWIW:
Westerbeke 20B-2 & 30B-3
Technical Manual ➥ https://www.westerbeke.com/technical...cal_manual.pdf
Parts list ➥ https://www.westerbeke.com/parts%20m...parts_list.pdf
More Technical Documents ➥ https://www.westerbeke.com/category/...BF634#techdocs

[Nefrut]

Hi JoeDoc, sorry for the late response.
Wasn't the governor spring or the exhaust elbow for me, it was an overheating engine causing a very small head gasket leak. Oil looked okay but I noticed some very light white smoke after running for a half an hour.

The engine was new to me and I didn't realize the temperature alarm had been disconnected. Ended up having to replace the thermostat and the head gasket.

I really don't like the Captain's panel with the alarms only. An alarm can stop working without you realizing it. Will look to hook up oil/temperature senders and gauges.