If it was a high speed jet issue then it would do the same thing on the muffs
Sent from my SM-G900V using Crappie.com Fishing mobile app
Printable View
If it was a high speed jet issue then it would do the same thing on the muffs
Sent from my SM-G900V using Crappie.com Fishing mobile app
Hope this is not the case as mentioned above but several years ago I tried out a used boat that done the exact same thing. It would idle all day and wouldn't get on plane at all. We took it back to the gentleman's house and he had a compression check ran on it the next day and one cylinder had zero compression. Hopefully his will be a fuel issue and nothing major. I wouldn't buy a used boat today without running a compression check first. They don't make a cheap powerhead.
I have a 1989 Mercury classic 50 and had a similar problem. Tried rebuilding the fuel pump, new fuel lines, draining the fuel tank and new fuel filter. No change. Finally took it in and they replaced the switch box and it ran like new.
If OP was just talking about spooling up up the rpms in gear on muffs then the jet could still be clogged. You spin up a motor on muffs to runaway speed at probably half throttle so a partially clogged jet could still be in play.
I would 100% check compression first. Then buy a real spark tester ($7) from the auto parts store and make sure each plug wire is sending out a spark that can jump a 3/8" gap. If it passes both then move onto fuel delivery or do a link and sync.
Keep in mind too that electric ignition components like the powerpack/brain box usually have a high speed and a low speed side. Meaning they can run great at 3000 rpms or below but whatever goes on in the inner workings of those can fail on the high side and the motor will never climb much past that. I've had it happen to me twice on two separate motors. It's unfortunate because those are always really expensive parts and sometimes they can bench test ok and still be bad...and sometimes they bench test bad but still seem to work. But I'd always save those for last unless you find a real cheap used one on Ebay from a good seller who took it off of a good motor. CDIelectronics.com makes aftermarket ignition components and should have a troubleshooting document on their site which will have the test specs for all of your ignition components, so I'd use that to bench test any component before you replaced it.
Bad news, #3 cylinder had 0 compression. Thanks for all the information though. He just learned a expensive lesson!
Now pull the head. Sometimes if one cylinder has no compression, vs just a very low number, but the motor still runs it can just be a bad head gasket. And if that's the case that would be good news all things considered. Resurface the head, clean the mating surfaces, and put a new gasket on and he just may be in business. I wouldn't get his hopes up though...but don't give up all hope either.