1987 85 hp -carb issues?

[hazmateer]

I just replaced one of the pistons. I was cruising at about 25-30 for most of an hour. But when i would push the throttle all the way in, it would get up to about 35, and then start to chug.

Is this possibly a carb/fuel issue? It sounds great and runs great between 25-30. It gets up and planes out fairly quickly as well.

Any suggestions? Seafoam it? Thanks.

 

[john from md]

Re: 1987 85 hp -carb issues?

It can be a carb issue and it can also be a timing issue. The first thing I would do is go step by step with the carb and timing set up in the book. This will set the trottle valves in their proper place as well as the choke plates and timing. By doing this, you have a base line on the engine and can troubleshoot effectively if you still have to.

 

[hazmateer]

Re: 1987 85 hp -carb issues?

Well I have another issue now. I went to restart a few hours after it was running. Now all it wants to do is backfire. It runs for about 2 seconds and spits and sputters. I cleaned out all the fuel lines, cleaned the carbs, got a new can with fresh gas.

Any thoughts why it is backfiring? Why it wont stay running?

 

[john from md]

Re: 1987 85 hp -carb issues?

It sounds like your timing slipped. This occurs from time to time when the Woodruff key in the flywheel is a loose fit. When the engine shuts down, the momentum of the flywheel works on the key. After a time, the key fails and the flywheel moves, thereby changing the timing.

That is the first place I would look. Also, since it has been backfiring, you need to check the fuel pump diaphram to make sure it is not torn. Because the diaphram operates from piston impulses, it is very sensitive to backfires.

Regards,

John

 

[hazmateer]

Re: 1987 85 hp -carb issues?

Ok, replaced the diaphram, put a new key on the flywheel (old one was still ok though). Got the motor to start. Still missing at idle, doesnt want to stay going until its warm. If I put it in gear it runs without missing. I took it on the lake and was cruising at 35 mp, so full throttle it seems to be going good.

Any one have an idea about the missing at idle? I dont have a timing light, but its the last thing i havent checked, could it still be a timing issue?

 

[john from md]

Re: 1987 85 hp -carb issues?

Tie up to a dock and adjust the idle speed to 750-800 in forward gear. Then, adjust the mixture while it is still in gear. Look for the best rpm but don't go below one turn out. Lastly, adjust the idle speed back to 750-800.

This will be the best you can do but it won't be perfect. Part of the problem is the racing plugs which tend to run cold, especially at idle. As long as she is not shutting down on you, you're good to go.

 

[hazmateer]

Re: 1987 85 hp -carb issues?

Isnt this easier to do with the muffs on in the driveway?

 

[john from md]

Re: 1987 85 hp -carb issues?

You can't set a boat engine up in the driveway because there is no back pressure on the exhaust. That is why the idle on the muffs is so high.

 

[hazmateer]

Re: 1987 85 hp -carb issues?

ok, thanks. I will give it a try tonight.