1972 Johnson 100hp v4 won't run at full speed

[jeepjack1995]

I recently acquired a 1972 Glastron Swinger with a Johnson v4 100hp power plant. I rebuild the carbs, replaced the fuel pump/hoses and spark plugs. The engine runs great in my driveway with the muffs on but when I put it in the water it backfires, smokes and won't run at full speed with the throttle wide open. My guess is that the back pressure from the exhaust being submerged is causing it to back fire... Anyone have any idea what could be causing this?
Thanks,
Jack

 

[racerone]

Sorry, it is not running " great " in the driveway.----Just sounds like it on 2 or 3 of 4 cylinders.----Trouble shooting needs to be done.-----Others will tell you what to check.

 

[F_R]

There are many checks and/or maintenance items. It has CD ignition, so at least the basics of that are working, or it wouldn't run. But it has a distributor cap & rotor that could probably use some cleaning. And spark plug wires that could be arcing out. And a timer base that may be sticking. Related would be the link & sync with the carbs. Speaking of carb, they might be fouled with gum & varnish from old gas.

And of course, spark plugs

Loose or corroded battery cable connections can spell death to the electronics. Read & heed.

 

[Bosunsmate]

Check compression and timing

 

[jeepjack1995]

I checked compression and spark tonight. I've got 120-125 psi at each cylinder and spark at each as well. However, the spark is weak. If I recall correctly I'm supposed to have a strong spark at 3/8" air gap. I don't have that. My next step is going to be checking and cleaning the distributor. If that doesn't work I'll be at a loss and unsure what I should test next. Any suggestions after cleaning the distributor would be greatly appreciated. Also, if anyone knows any tips/proper procedure for cleaning up/ lubing the distributor, that would be very greatly appreciated.
Thanks,
Jack

 

[jeepjack1995]

I checked compression and spark tonight. I've got 120-125 psi at each cylinder and spark at each as well. However, the spark is weak. If I recall correctly I'm supposed to have a strong spark at 3/8" air gap. I don't have that. My next step is going to be checking and cleaning the distributor. If that doesn't work I'll be at a loss and unsure what I should test next. Any suggestions after cleaning the distributor would be greatly appreciated. Also, if anyone knows any tips/proper procedure for cleaning up/ lubing the distributor, that would be very greatly appreciated.
Thanks,
Jack

 

[Bosunsmate]

On my tractor i lightly sand the contacts, sorry thats all i know about these systems.
Try pulling off each plug with insulated pliers and checking there is a change in rpm. Its a drop test, itl tell you if any cylinders are not working

 

[jeepjack1995]

Got the distributor off this weekend. It's got a crack in it and some burn marks. Ordered a used cap and rotor. hopefully that fixes my problem. I read somewhere about lubing the anti reverse spring with some dielectric grease. is there anything else I should grease while I have it apart?
Thanks for all the help.

 

[Bosunsmate]

yep crack and burn marks can have carbon in them and that will cause shortin
Generally you want less grease etc in there as that can collect dust but the spring you could a bit

 

[racerone]

The factory manual calls for grease on that spring !