3.0L no wot power!!

Blake2342

Recruit
Joined
Jul 11, 2012
Messages
2
I have a 1985 mercruiser 3.0L in a fourwinns 16' with a 17 pitch prop. For the past few years the boat just hasn't run properly(low power hesitation won't stay running), this year I felt an urge to get it running right. So far the impeller has been changed, new fuel line to fuel pump, cleaned the carb(not sure if done well enough), changed the spark plugs(last year), new ignition coil, new points rotor and cap, new wires, and a refreshed fuel pump(mechanical).

The boat was having starting issues and generally just didn't want to run found out it had a bad distributor cap. Replaced it and then got the timing of the motor done by a friend not so sure what he set it all to but it started and idled rough it also revved but the boat ran rough and popped allot. Replaced the Ignition coil as its nuts were loose and couldn't be tightened, at the same time I replaced the wires and spark plugs. The boat ran a little better but not much. So I cleaned the carb(took it apart and sprayed most of it with carb cleaner) and then tuned the idle circuit screw, boat then started and idles fine(as in it doesn't die, still a littler rough though could be the bad mounts). The boat ran fine with the muffs on, it would start no problem and it would rev up to 5000 rpm no problem.

So thinking my problems were over I took it to the river started the boat left the dock and gave it throttle and it started to pick up but as I added more throttle nothing happened tone of the engine got deeper but the rpms would not climb above 2800 rpm and occasionally it would backfire out of the carb. No matter what it would not climb any higher, only had myself and a friend on the boat. Went back to the dock and thought for a moment and came to the conclusion that the power valve must be stuck causing it to run lean and not get enough fuel to get running higher and also caused the carb backfire. Pulled the top half off and cleaned the power valve and the spring loaded thing that pushes on it until I was out of cleaner. By this point it would move in and out with little fuss(slight resistance but always dropped back down). Took it out on the water again and nothing changed, still won't get above 2800 rpms under WOT. Got to frustrated and decided to call it a day.

Please any advice will be much appreciated!!
 

QC

Supreme Mariner
Joined
Mar 22, 2005
Messages
22,783
Re: 3.0L no wot power!!

Replaced it and then got the timing of the motor done by a friend not so sure what he set it all to but it started and idled rough it also revved but the boat ran rough and popped allot.
This seems unresolved to me . . .
 

fishrdan

Admiral
Joined
Jan 25, 2008
Messages
6,989
Re: 3.0L no wot power!!

Pop the cap off the distributor, grab the rotor and turn it, does it have tension, is it smooth and spring back to the same place all the time?

While in there I'd pull the points plate and inspect the weights and springs (what you were testing turning the rotor) and make sure the springs are in good condition, weights free and pivot points lubed up.

Also,,, when the rotor is off, push/pull the distributor shaft fore/aft/port/starboard and see if it has any play, you shouldn't be able to "feel" it rocking around. If you can, the bushings are shot and dwell will be all over the place.
 
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