lost 800 rpms at wot

[blrnar]

Re: lost 800 rpms at wot

Changing out the plugs and wires overall made very little difference. Since day one of purchasing this boat which was in the spring the Starboard engine has always been the weaker of the two for throttle response and smoothness. Switching out distributors is no big deal, just a matter of positioning engines at TDC, marking them for timing reposition(aprox), then removing the distributors, and re-installing, then you must re-set timing. I do not know what tools you have available as this was an easy task for myself with the proper timing light etc. And yes removing the spark plug beside the water heater was a royal pain, much more difficult than swapping distributors. I will post my results on Monday.


Brian

 

[stu man do]

Re: lost 800 rpms at wot

Brian,
Sure hope the distributor switch works. It does seem like the ignition advance is not working properly.


Have you ever checked for an exhaust restriction. (pulled outdrive, or impeller, or exhaust manifold)) It does not seem logical with the size of the exhaust manifolds and piping to outdrive, but again trying to think of the common parts, that a piece of impeller is lodged somewhere restricting exhaust? In my past posts, I had a undercooling issue on this engine and it was caused by small pieces of old impeller getting stuck in the thermostat. That issue has been resolved, running at just about 160 degrees now.

I do not have the skills or tools to do the timing myself, was thinking of just marking rotor position on both and then adjusting so they match rotor position when they were pulled. Will that work? (hard to explain)

If it is the distributor, then I will have the engines timed by the local shop. (they tell me you have to have the computer to time properly)

Thanks,
Jeff

 

[blrnar]

Re: lost 800 rpms at wot

Yes as long as you bring both engines to TDC on the compression stroke and mark the position of the distributors in the block then they can be swapped out. Also I could be wrong but to set the timing on your engine you should just have to put the engine in base timing mode by plugging a shunt(available from volvo for $10) into the distributor and then setting the timing with a timing light(one that has the advance feature built into it either a dial on the timing light or digital)


Brian

 

[stu man do]

Re: lost 800 rpms at wot

Brian,
before I mess with the ignition, I figure I will wait until I hear if it solved your problem. I just ordered the riser exhaust gaskets, going to pull the riser elbows and pipe to see if I have any exhaust restrictions. This way we are tackling two areas rather than just one. I bought the boat used, so I am not sure if it was ever used in salt water. The other thought is that maybe impeller pieces are stuck in exhaust manafold and causing restriction. Worth
a shot at this point in the summer, and I havelimited abilility and know how when it comes to distributor timing. I don't want to screw both engines up. in researching the exhaust restriction, they have changed out the gaskets to the risers for some reason, not sure why. I do have a little rust on the bolts attaching the riser. Will let you know what I find.

 

[blrnar]

Re: lost 800 rpms at wot

Jeff,

I took the boat out today for a water test and the rpms did increase however the engine surges into the proper amount of trimmed out rpms(4850 on both engines) with a gps speed of 48 mph. But like I said it surged by 200 to 300 rpms at w.o.t. When at 1500 rpms it surges by 100 rpms so I now have to determine the cause, this boat is becoming a real p.i.t.a. I will let you know the results.


Brian