1990 Johnson Wet spark plugs, no rpm

[stifeout]

Hi folks what a great site!Glad you exist!!
I have a 1990, I think , v6 Johnson (150). Bought it with bad head gaskets. I replaced them. Boat ran great for 3 trips.
Last trip out, It was alittle hard starting but OK. When I went to Full throttle, it would start missing right away and would shut offat around 3000 rpm. It had no problem restarting but then can't get it over 1500 without misfires. Pulled the plugs at the dock and noticed they were oily and wet. replaced them, drained bowls, (ckecking for water) and restarted. Same thing. I also pushed the choke as engine ran to check if choke was stuck closed, it would kill the engine, so I assumed that wasn't it?
When I took it home and started it (runs ok at idle but definitely hear a mis) I put my hand on cyl heads and noticed that they were just warm. I also noticed that the plugs were also, just warm.
When I did the head gaskets I did not put in the thermostats, I took them out and just left a restricing part of them.
So probably opertating temp is too low, but it did it run real good before? I live in S Florida water temp doesnt change that much?? Should I try a hotter plug? Is a higher number, a hotter plug?
Thanks again Please Help!!:'(

 

[ezeke]

Re: 1990 Johnson Wet spark plugs, no rpm

First thing to do is a spark test, then a compression test, and then get the thermostats fixed.

Check the spark and compression with all plugs removed.

You should see a sharp blue spark across at least 3/8" on all plugs.

Compression needs to be within 10% on each cylinder.

BTW, Whenever you put in new head gaskets, you need to retorque to spec after a break in.

 

[stifeout]

Re: 1990 Johnson Wet spark plugs, no rpm

Sorry, one more thing, I noticed that the motor smokes a bit too much, didn't notice that before. Using 40:1 ratio synthetic blend penzoil. Also engine revs freely in neutral and fairly freely in reverse, but misfiring.
Thanks again.

 

[stifeout]

Re: 1990 Johnson Wet spark plugs, no rpm

Wow.. thanks commander for the quick reply. I did check spark, it was good. I did re torque after both previous trips, all torqued.
Will do compression test. Can I use regular auto tester, and do I need to run comp test at Full throtle? Thanks

 

[ezeke]

Re: 1990 Johnson Wet spark plugs, no rpm

That oil is what I use and it should be OK. 100% synthetic is even better "they" say. The fuel oil ratio is 50:1.

Thermostats will help with the smoke, so will the oil ratio at 50:1.

When you have time you should fix the recirculation check valves, but you will have to pull the carbs to get to them all.

Auto tester is fine but get one with a screw in head.

Compression test with all plugs out. Raise the warm up lever if you want, but it makes no difference on a two stroke..

 

[stifeout]

Re: 1990 Johnson Wet spark plugs, no rpm

Thank you again Ezeke!