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
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.