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bosborn

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OK all, I've been reading all of these threads and I cant seem to figure out my motor... Its a 1990 90hp crossflow Johnson. It starts, idles revs on muffs to about 4800. When in the water it wont get above 2000 rpm. I have replaced the fuel bowls, fuel pump, fuel lines, rectifier regulator, stator, plugs and been through the cabs 3 times. It runs smooth at 2000 in the water just no power. I have also timed it and replaced the roller on the carb shaft. The other question I have is how many volts should the charging system put out? I have pretty much replaced the whole system and it still only puts about 12.3 at the 2000 rpm. Any help would be appreciated...
 
Also at mid throttle it seem to have a small miss in the water. I have checked the spark it jumps a half inch gap no problem. I have also synced everything. I also ran a compression check it was 111,117,111,116.
 
What does your battery read when disconnected? Just a thought maybe a bad battery is contributing to your charging issues. I'd go through your carbs a fourth time... I recently had similar running issues. Racerone was a huge help.
 
The battery reads abut the same 12-12.3 depending on what I'm doing. If I use the TNT it drops to about 11.7 then comes right back to 12 while its running. When I unhook the cables it is right at 12V. I am not sure about the coil wires. I will check when i get home. Should the orange/blue be on top?

Thanks again
 
The coil wires are on the right cylinders. I did a drop test. Cylinder number 2 did not change the engine. I swapped coils with number 3 it didnt change. I swapped plug wires with number 4. It still didnt change. The compression is good it is 111. The plug is wet with fuel. Power pack? When I unhook the plug wire while running I can hear a spark somewhere. I cant see it. Sometimes when I put the wire back on i can still hear it. Other times it goes away. If the power pack is bad will it just kill one cylinder?
 
Maybe you just need a new boot on the end of the plug wire.-----Do you understand what a powerpack is / what it does / how it all works ?
 
I do have an idea how the power pack works, I am hoping maybe your insight will guide me in the right direction. After I heard the spark I did swap plug wires with number 4 cylinder. Number 2 still didnt change when I unhooked the plug wire. I still heard the spark somewhere around the number 2 coil or wiring. I am wondering if voltage can jump from the primary wire going to the coil since the power pack has a capaciter in it. Is it possible that just one of the SCR's in the power pack could be bad? If not and I have compression, fuel and spark where do I go from here?

Im getting frustrated....

Thanks again,
 
Your motor sounds like it might be running on 3 of 4 cylinders.----Those compression numbers are not encouraging.-----Removal of the bypass covers will cost you a few dollars in gaskets.----Allows you to inspect pistons and rings.---Or perhaps there is a reed valve stuck open.-----It should not be hard to determine what is wrong with your motor.----You say spark jumps a gap of 1/2 " so likely you do not have an ignition issue.---More trouble shooting is required , not part replacement guessing !-----Flywheel is good and nut was torqued to 100 ft-lbs ?
 
After running it a while doing these drop tests I decided to do another compression test while it was a little warm, the cylinder thats not firing is 95 the one below it was 100. the other side was 105. Then I noticed water on the number 4 plug. I replaced the head gaskets this winter because of the same reason but in another cylinder, but I decided to pull it anyway. It definitely has water in number 4 cylinder. I dont see anything absolutely wrong with the gasket, but I am going to order an original. I put an aftermarket on the first time. I will pull the bypass covers also. Ill update the post later this week when I get it back together....

Gotta love boats.....lol

Thanks again
 
Well......still not good. Makes no sense to me... New head gasket, new coil, new wire. Still no reaction when I do a drop test on the #2 cylinder. 100 psi compression, good spark and its getting fuel. Pulled the side covers pistons look good no scuffing and rings are free. Still getting water in number 4 even with new head gaskets, but its almost dies when I pull the plug wire on that cylinder. Where else would the water be coming from? Why wouldnt number 2 be firing with spark fuel and compression?
 
Was head checked for flatness and prepped,Rolled in a figure 8 pattern on plate glass or a plate of steel with 220 grit wetor dry? BLOck needs to be addressed also, I use a huge flat file
 
Head was flat. I used 320 paper on a granite counter...Wife wasnt happy, I scraped the block and did the best I could with a straight edge to check it. Any Ideas on why the other cylinder isnt firing right?
 
Im going to pull the exhaust cover this weekend I was reading somewhere that there could be a corrosion hole in under that plate. Has anyone ever heard of this?
 
Update, I pulled the carbs again tonight and found another set of jets in the bowls. I think these might even be the actual main jets. Wouldn't ya know it the one for the cylinder that wasn't firing was plugged tight. As for the water in the cylinder I'm still kind of up in arms. I pulled the head again and ran it over some 180 on the granite again. It still had a low spot in the area that looked to me like water might have been coming in. I sanded it until the spot went away. I will run it Friday night and update again.
 
Boat ran well Saturday. No water in cylinder and it was hitting on all 4. The only issue I had was if I idled for a long period then it would load up.

Thanks for all your help.
 
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