Thread: Boat Mechanic Help

Post your questions here. Often people know the answer but don't know they do because they don't know the question. Another words the question joggles the memory.

Originally Posted by Barnacle Bill

Post your questions here. Often people know the answer but don't know they do because they don't know the question. Another words the question joggles the memory.

yep I have a '77 85 horse Johnson and maybe I can help, not to good with the mechanics but do know a little.

Ok here goes, Was running great on a 24 foot pontoon, then started missing, ran for 1/2 mile or so that way then the motor smoothed out but don't have the top end speed now. I was running right about 22 mph now only getting 14. Don't have an rpm gauge, but here is what I have done.
130 psi compression on 4 cylinders
Changed plugs
Changed gas tanks and lines
Have good spark
Just tore down the carbs again yesterday and cleaned really good. Going to the lake in the morning to see how it goes, ill post with the results. Thanks so much for the responses and maybe I can get it lined out.

Well no luck at the lake, motor idles fine and when i first took off it jumped up to 20 mph and then missed, kicked and bucked till finally after a few mins it just smoothed out but back down to 15 mph. Everyhting else works like it should, starts and idles great. Any ideas?

My motor lost power like that. I chased that rabbit 47 different ways but new plugs and a top end decarb fixed it. I did several of the things that you have done. Replaced fuel lines, cleaned carbs. Did you remember to set the gap on the new plugs? You might try doing that top end cleaning. I had a whole lot of black gunk come out of mine. I used the Seafoam in the spray can. I ran the motor 10 minutes in a cut down plastic drum to get it up to temp then sprayed nearly a whole can of the seafoam through the carbs. It would die every once and while and I'd just crank it back up and keep spraying. I let it set for 30 minutes then cranked it back and ran it at idle for a couple minutes then slowly revved it up to around 3000 rpms and let it run for a couple minutes.

Have you checked the timing? That would effect it too.

I guess in your case, the first thing I'd do is rebuild or replace the fuel pump.

Disclaimer: I AM NOT an outboard mechanic but I just spent weeks working through a problem on mine.

Well been working on this motor now most of the afternoon and after doing all that was mentioned including a new fuel pump, a guy called me from here and told me to check the spark in the dark and guess what? I found the culprit, one cylinder is only firing once in awhile which would explain why i only can get 15 mph I'm running on 3 cylinders, gonna pick up the new spark coil tomorrow and hope that's all I need lol. I want to thank this forum and the guys on here for all the help they have provided, maybe and I can return the favor. God Bless

That's great man. Glad you got it figured out.

You should have just swapped coils to verify that is the problem. If I am reading you right the problem occurs once the motor has warmed up. If so I'm betting a component(s) in the power pack is breaking down from the heat.