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1988 johnson gt 150 possibly wrong carburetor

C

Chuckd

Member
I had many little issues I've tried to nip, now there's another. I'll start with what I've done.
Had a spark not firing, so replaced coil, now works. Had leaking fuel lines, replaced them all. Cleaned carbs and put new kit on them as well as a link and sink. Replaced regulator, rectifier. Impeller kit installed. Timing checked. Fuel filter replaced.

Problem that I have is the boat is a little slow out of hole, and wot is 4400 rpms at 50 GPS mph. I have a 24p prop, and tried a 19p prop but only gained 600 rpms. This motor should sling a 24p prop, with good compression.
So, I looked on the net and noticed this motor (j150stlcca) should have a 1 3/8 carb, but the one I have has the 1 5/16 carb ????? Could that be the issue? The reason I am - 1000 rpms?
 
faztbullet said:
Nopes that's correct carbs.....it has a cylinder not firing/down
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How do I check for that? Compression tested fine and all plugs are new, and tested the spark with a spark tester at 7/16 gap all fired strong. Also according to every parts list for this model that I could find calls for the 1 3/8 carburetor and has different jets. I did more research and it shows later model gt 150s running the 1 5/16 carburetor
 
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1 3/8 carbs only used on 235hp and some 175hp. Its either lean or timing/carbs are not opening up or cylinder not working. Usually if its 1000rpm low its only running on 5 cylinders. Need to take a timing light and test each cylinder at 3500rpm with a load.There is a TSB on these motors as they burn the wires off in the bottom of spark plug boots....
 
faztbullet said:
1 3/8 carbs only used on 235hp and some 175hp. Its either lean or timing/carbs are not opening up or cylinder not working. Usually if its 1000rpm low its only running on 5 cylinders. Need to take a timing light and test each cylinder at 3500rpm with a load.There is a TSB on these motors as they burn the wires off in the bottom of spark plug boots....
Click to expand...

I will check it, what is a tsb?
 
There was some kind of black gunk all over the wires in the boot, so I have cleaned them. Do the plugs look normal for 3 trips to the lake?






 
faztbullet said:
The bottom 3 insulators look washed....check spark on that side as stator could be weak .
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I checked the sparks and they are good with the spark tester set at 7/16. I'll check the spark again with a time light , it'll be a few days before I can go to the water to put load on. Is the between the wires on the cable look to be an issue? The gunk is between wires and the copper coil.
 
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I just test the stator per clymer. First test between yellow wire and ground reads infinity. 2nd between yellow/Gray and ground reads infinity. Next with low ohm scale , leads placed between yellow and yellow/Gray wire show .6 . My meter doesn't zero out, it reads .4 when I touch leads together. So if I compensated for that resistance, then it would be .2 . The book says should be between .12 to .22 on 35 amp system. So what do you think, check power pack on that side? Would it fall out when trying to wot?
 
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I retested the with the 2000 ohm scale on brown wires and it reads 970 on both sides. But sometimes it read ( hv 9.62 ) but maybe it was bad connection because I don't know what that means.
 
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