J4C or J6C? Please help..

[55'Fleetwin7.5]

I run a 1965 Starflite 90S.. I changed the plugs today. The plugs I removed were J6C. I had it on the lake today with the old plugs and (except for running a bit hotter than I like.. which is another issue..) It idled, shifted and ran reasonably. The plugs were old and I had read that the correct plug was actually a "J4C".. So that is was I installed. When I started it with the new plugs, it idled way fast.. 3500 to 4000... SO I shut it down. Now I believe the impellor needs replacing... Could the change in plugs do that? I tried to shorten the throttle cable to help me get it slower, but it did not accomplish much.


Also,I am not getting the strong water flow I want and after about 30 seconds at that high RPM, I could not stand to touch the cylinder head.. I am not sure about replacing the impellor on this model.. I have done several from 5.5 hp to 35 hp, but none with electric shift. Any advice?

 

[Joe Reeves]

Re: J4C or J6C? Please help..

The normal (1st choice) spark plug is the J4C with the recommended alternative plug being the J6C. Many engines show a somewhat improved performance, either the idle or the full throttle range, with the J6C .

Changing spark pugs would have absolutely nothing to do with the engine rpm UNLESS the engine wasn't running on all cylinders with the old spark plugs.

Tie either a strong string/cord of a piece of flexible wire to the electric shift cable so that you can easily snake it back up when installing the lower unit.

Best to install the complete water pump assembly if available.

 

[55'Fleetwin7.5]

Re: J4C or J6C? Please help..

Thanks for the info on the spark plugs...

Regarding th e pump, I see the inspection plate where I would have disconnected the linkage on a traditional shifter.. Inside there is another door where the wire enters( for the electric shift)... I assume that if I remove the two screws to that second door, I will see a wire pair connection. Is that the wire you suggest I secure with a cord or wire?

Additionally, This is a long shaft as best as I can tell.. it has that mid section added. Do I find the pump assembly right below the midsection piece? I expect that the once I remove the bolts, the lower portion will drop away from the drive shaft... is that true? or will I need to deal with the drive shaft in some way?

Then replace the entire pump assembly, snake the wires back up.. replace the bolts and viola!

Is that about right?

If I am missing something, please advise...

Thanks,

Tom

 

[Joe Reeves]

Re: J4C or J6C? Please help..

That second plate you speak of should have the electric shift wire leading from the lower unit, protruding out of that second plate, and traveling from there up to the powerhead area where those electric shift wires would connect to the engine's wiring harness. I assume by what you've said that you haven't looked into that area yet.

Water pump sits atop the lower unit..... you can't miss it.

The rest is about right.

 

[55'Fleetwin7.5]

Re: J4C or J6C? Please help..

Thanks Joe,

Do you disconnect the shift wires up at the powerhead? or at the midsction...

The reason I ask is that I do not see any connectors up at the powerhead... just wires going into the main loom..

Thanks,

Tom

 

[Joe Reeves]

Re: J4C or J6C? Please help..

Remove that 1st side plate, then trace the shift wire upwards to their connection point.