Help with Force 150 ('91 J)

[planecrazy29]

I recently bought a 26' Bayliner Rendezvous deck boat with a 150 Force O/B. The engine would only turn 2800 at WOT with a 13 3/4 x 17 prop. I replaced plugs and swappped prop to a 14x11 (as recommended by Michigan Wheel). I now get 3400 @ WOT with the same top end. I just tonite checked the carbs and re-sync'ed and check the timing cam per the service manual. I read up on de-carb'ing and will do that tomorrow. Anything else that I should check? I'm not looking for speed with this boat, but the engine should be turning up to 5000 if it was working properly (or should it?). TIA for any help.<br /><br /> -Aaron

 

[roscoe]

Re: Help with Force 150 ('91 J)

Check the compression on all 5 cylinders.<br />Check for a strong spark on all 5 plugs.<br />And check for fuel to all cylinders.<br /><br />Yes it should be running up around 5000 rpm at WOT, or the motor won't last long.

 

[planecrazy29]

Re: Help with Force 150 ('91 J)

Compression around 145 all cyl. (done by the shop before I purchased). When I changed the plugs (champion l76v to NGK BUHM) they were all fouled and wet so I'm pretty sure that all cyl. are getting fuel. How would you suggest that I check spark "strength"? It starts and idles fine and voltage to the ignition is 14v anywhere past 1000 rpm. Any other suggestions?

 

[planecrazy29]

Re: Help with Force 150 ('91 J)

I'm going to bump this back to the top with an update. Hopefully someone will have a suggestion.

In addition to the above, I have rebuilt the carbs and fuel pumps and de-carbed the engine using seafoam. I also replaced the water pump as a preventative measure. The engine seems to run great, just not up to snuff. It idles and transitions great. At WOT (3400-3600) it is very noisy and seems to be laboring. If I back off to 3000 it's as smooth as silk. Only other observation I have made is that it seems to drop a cylinder after 20-30 min @ 3000. I believe this is due to plugs fouling since I can't get the cylinders to operating temp. I am at a complete loss here. Any one have any suggestions?

 

[eurolarva]

Re: Help with Force 150 ('91 J)

Auto parts store such as autozone sells spark testers. A 3/4 inch screw stuck in the plug wire and then spaces about 1/4 to 1/2 inch from ground will work. It should jump a nice blue spark about 3/8 inch on each cylinder. It sure sounds like one cylinder is the problem. If spark test passes on each cylinder pull the plugs and verify each has the same wear marks such as black, grimy or oily. If one looks even slightly different focus on that unit. If that cylinder fires a good spark get a compression tester and re test that unit.

 

[Bradforce]

Re: Help with Force 150 ('91 J)

I have the same motor with a 13 1/4 X 17 pitch on a 21 Trophy walk around. I run about 5500 rpm at wot. I am not a mechanic but I would guess that the problem is not your prop
Brad