'79 Johnson 115 No power

[Spicy_McHaggis]

Ok here we go, I have a 79 Johnson 115. I've had it 6 years or so now and feel I'm chasing a ghost. I consider myself quite mechanically inclined and am about to give up on this thing. When I first start it up cold it runs very well but has maybe half the power i know it has. If I start it up and let it run for 10min or so then walk away for half an hour, when i come back it runs like new. I have tried everything I can think of. I have rebuilt the entire motor last year, all new pistons and total gasket kit. All four coils have been replaced, Carbs cleaned, fuel pump rebuilt. I am lost and could use some help!! Thank you to anyone who replies!

 

[ezeke]

Re: '79 Johnson 115 No power

Have you run it using an inductive timing light to watch for firing problems?

Have you run the boat at WOT for any sustained period?

Do you have a water separating fuel filter and if so have you dumped it lately?

 

[emdsapmgr]

Re: '79 Johnson 115 No power

I'd follow ezeke's recommendation on checking with the timing light. Electrical problems show up once the engine reaches normal operating temps. That may be why it runs ok when cold.

 

[Spicy_McHaggis]

Re: '79 Johnson 115 No power

No I've never used an inductive timing light. I run the boat like any normal boat when it is running at full power, WOT most of the time!!

"emdsapmgr
I'd follow ezeke's recommendation on checking with the timing light. Electrical problems show up once the engine reaches normal operating temps. That may be why it runs ok when cold. "

It doesn't run good when cold it runs at half power when cold, then when warm runs great!

I do not have a water seperator on the fuel line but the tank was drained at the end of the season and I just put the boat in the water about two weeks ago with fresh gas.

 

[emdsapmgr]

Re: '79 Johnson 115 No power

It helps to know if you are chasing a fuel issue or an ignition issue. It's pretty easy to check for ignition spark on all plug wires with a timing light. Once you know that it's firing ok, then turn to the fuel side. It is not unusual for excess fuel/oil to collect in the bottom of the airbox, esp if you tilt that engine after using. When first started cold, that excess fuel will be recirculated through the airbox drain hose to the bottom cylinder. This may cause temprorary excess fuel in that cyl and it may not fire well and it may smoke for a minute until the excess fuel is burned off.

 

[Spicy_McHaggis]

Re: '79 Johnson 115 No power

I don't have a timing light but a buddy is bringing one over today. I am taking the boat out and I actually always tilt the motor up when I am done. Except the last time I went out I left it down, we'll see if that helps(I hope it's that simple). You are right, the engine does smoke quite a bit when I first start up. I'll let you know how it goes later. Thank you so much for your help!!!!!!

 

[Spicy_McHaggis]

Re: '79 Johnson 115 No power

Just wanted to thank everyone for their help on this motor. It ended up being a powerpack and a cloged inline fuel filter.