98 Johnson two problems

[coafdm6]

I have a 98 Johnson that has two issues perhaps unrelated?

1. It does not idle, I have replaced the plugs, compression at 150 both cylinders. Increasing the idle make run for a while then it seems to miss and coughs and shuts off.

2. Second issue is the engine is low to plane, once there it runs fine at 6300 rpm, smooth and all.

Sooo, won't idle and slow to plane, once there, runs great???

 

[WillyBWright]

Re: 98 Johnson two problems

Welcome to iboats.

6300 is high for any Johnson, let alone a twin. I'm betting on varnish in the carb(s). You'd have to disassemble to clean propely. That's about all I can offer not knowing more, like what Hp.

 

[Silvertip]

Re: 98 Johnson two problems

Let the engine idle and just about the time it begins to cough and die, push the key in (primer). If the engine comes to life again, you either have a carb problem or the idle speed and idle mixture need to be tweaked. If that doesn't help, carb rebuild is probably necessary. I agree with Willy that 6300 is too fast for that engine and in fact, the rev limiter should be kicking in about that speed. Of course it could be the tach is not reading correctly.

 

[drJ]

Re: 98 Johnson two problems

I have a two cylinder Johnson 50 hp 1999 and have the same exact two problems. The engine doesn't want to idle at all but then wants to run at 6500 rpm at the top end. I wonder if it is the timing because I have already rebuilt the carbs.

 

[coafdm6]

Re: 98 Johnson two problems

Mine is a 50 HP Johnson, 1999.

I have rebuilt the carbs and fuel pump.

Changed gas today, it runs much better but still not smooth.

Should the gas filter (OMC) be filled? I pump it up but as it runs it goes to a low level? Is there a level that it should stablize at??