85hp Johnson runs great for a couple minutes then starts hiccuping...

[TeamPSI]

I took my boat out today after a spark plug change to see if it ran any better out of the hole than it did last week. I moticed that the motor had a lot more get up and go and it didnt go dead like before.

This was the first time I had gotten to open it up for a period of time longer than a minute. The motor runs GREAT for a couple of minutes tehn it all of a sudden starts to hiccup, loses power, and more or less will studder itself to death if I keep in the throttle. The motor will, however, idle just perfectly during this time.

Now for the weird parts....
If I let the motor sit for 5 minutes or so, it will run perfectly again (just for another couple of minutes). It doesnt seem to be hot at all.

I pulled all of the plugs after it had done this and moticed that the #1 plug was really clean. It had just a little oil on it and that was all. The other three looked black.

I put the old plugs in to try it just for shits and giggles and it definitely lost its low end power.

The motor is a 1971 Johnson 85hp 2 stroke.
Any thoughts?

 

[R.Johnson]

Re: 85hp Johnson runs great for a couple minutes then starts hiccuping...

I would pull the flywheel, and check the point setting's. Also, check the distributor cap, and plug lead's , and anti-reverse spring at this time.

 

[TeamPSI]

Re: 85hp Johnson runs great for a couple minutes then starts hiccuping...

Alright!

I also forgot to mention that if I raise the start lever to high idle after the motor is in this "angry mode" it is VERY sluggish to bring the rpm's up.

 

[R.Johnson]

Re: 85hp Johnson runs great for a couple minutes then starts hiccuping...

That engine has what is called a battery, capacitor discharge ignition system using breaker point's. You are going to need a manual to guide you through this system.

 

[TeamPSI]

Re: 85hp Johnson runs great for a couple minutes then starts hiccuping...

I have a manual for the motor but I dont have any fancy ignition testing equipment. I have a DMM and thats about it.

I wouldnt have any problems setting the .010 gap in the points but from there I'd be in unknown waters.

 

[reeldutch]

Re: 85hp Johnson runs great for a couple minutes then starts hiccuping...

check also for vacuum or an airleak in your fuel system.
and fuel pump presure.
sounds like at higher rpm your motor starts starving for fuel.

you might have a fuel restriction somewere.

put a 8" clear vinyl hose inbetween fuel filter and fuel pump.
check for bubles.
if you see a lot of bubbles this could mean an fuel restriction wich will cause vaporizing, or you could have a airleak.

is the "clean" plug wet or dry?

if its dry its not getting any fuel.
check the carb. may be clogged high speed circuit?

if its wet it is getting fuel but it doesnt ignite for some reason.
check ignition system, like R.johnson explained.
good luck

 

[R.Johnson]

Re: 85hp Johnson runs great for a couple minutes then starts hiccuping...

Joe Reeves has posted a full page of instruction's for trouble shooting this system if you should need it.

 

[TeamPSI]

Re: 85hp Johnson runs great for a couple minutes then starts hiccuping...

OK... where would I find that page?

The "clean" plug is wet.

I'm just very confused about it I guess. It sure does run perfectly at first.

 

[ezeke]

Re: 85hp Johnson runs great for a couple minutes then starts hiccuping...

It would be very possible that you have a blown cylinder head gasket.

 

[TeamPSI]

Re: 85hp Johnson runs great for a couple minutes then starts hiccuping...

Update...
I found out that the #1 plug wasn't firing due to the wire not being screwed in properly. The threads on that wire are sort of bad. I swapped it with another wire and got the both to thread. The motor is leaps and bounds better than before, as you could imagine.

I reset the points and just visually inspected everything else. I made sure that I was getting plenty of spark on every cylinder.

The sputtering problem still arises after a few minutes of running though. It is not nearly as bad now because the motor has 4 plugs firing. The motor doest go dead now, but it does spit and sputter a lot. It feels like I lose about 5-8mph and a good bit of power.

I tried priming the fuel bulb when this was occurring and it didn't help any.

Head gasket eh? I did a compression check and it tests well.

 

[tashasdaddy]

Re: 85hp Johnson runs great for a couple minutes then starts hiccuping...

look at this, just maybe
http://www.iboats.com/bbboard/bbBoard.cgi?a=viewthread;fid=28;gtid=818798;gpid=818802