1988 25hp stresses in gear

[bostonwhaler88]

I have an 88 25hp on a boston whaler.

The engine will start and idle fine, it will throttle up to high rpm, but once it is in gear the engine seems to stress and will only run at about 1/4 max speed.

I am completely clueless after checking compression, carb., sparg plugs, spark wires, switched ignition coils.

Interesting to note; when i ran on just one cylinder (removed spark plug) the boat only started when the top cylinder was connected.

Spark plug diagnosis:
cylinder one (top): some oil residue
cylinder two (bottom): dry, smoke in cylinder after running for 15min

Any HELP would be much appreciated

 

[KIGuy52]

Re: 1988 25hp stresses in gear

Same problem I had with my old 25 Merc a couple of years ago. Sounds like the switchbox needs to be replaced. That's the plastic box located on the side of the powerhead with a bunch of wires running to it. It's an easy job, just make sure you tie the wires down in such a way that the flywheel doesn't rub against them. While you're replacing that, I suggest you also replace the trigger, which is located under the flywheel. It's mounted on a plastic ring that wears out after a while. I got my parts from BAM Marine (aka Mercruiserparts.com). Good prices and excellent customer service. My parts arrived in 3 days.