1986 15hp johnson head swap

[sahendo]

I have a 1986 15hp johnson, J15ELCDE. I'm looking for a cylinder head, my part# is 329917. I wanted top know if anyone has swapped theirs out with a different head, or if there were any other ones that would fit it? The older ones look similar, but didn't know for sure if they would work or not. Any ideas or suggestions?

 

[ondarvr]

Check part numbers, many are compatible.

 

[racerone]

Any of them to 1992 will fit.----------Just find a later one with the easier to service thermostat.-----A stripped plug hole on yours ?----------helicoil is the easy fix.

 

[sahendo]

Yes racerone, the owner before me didn't tell me about the stripped plug hole on the motor. It was running a little rough so went to change the plugs and clean the carb. When I backed the one plug out the heli-coil came with it. And I don't think the heli-coil was installed properly, once I took the plug out I could see carbon around the base of the plug, like the cylinder was leaking.------ So I figured just get another cylinder head. --------So your basically saying any 9.9 or 15 from what, early 80's to 92 should work?------ I seen on the early ones, the dome of the cylinders were shaped a little different.

 

[flyingscott]

Have a machine shop put an insert in it better than heli-coils..

 

[sahendo]

Here's what I found, basically it looks like any cylinder head from 74-92 would work. The earlier ones 74-76 have a 7 bolt thermostat cover, the mid years 77-86 have a 8 bolt thermostat cover and the cover is notched around the spark plug holes, the later years 87-92 have a thermostat that is easier to service but you may have to do a little work to get everything to line up. And you cannot use your old engine cover cause the thermostat sits too high and the cover will hit. Found it on leeroysramblings.com. Thanks for all the advice and help.

 

[oldboat1]

The newer head cover (t.stat on top) should fit under your '86 hood.

 

[oldboat1]

There's more to say about the thermostat cover on the 9.9s and 15s. The older covers with the thermostat at the bottom are fine, but a little trickier to install. Because the clearance is really tight, the head cover needs to be removed to service the t.stat. That's not hard, although there is a little trick to removal and replacement of the head cover as well -- need to leave the two bottom bolts in the cover after loosening from the head (removal). To replace the cover, the two bolts need to be partially inserted through the cover before dropping it in place. Procedure for R and R of the head cover is the same irrespective of the type of t.stat cover. The newer head cover gives you more space for plug and ignition wires, though -- old t.stat cover made clearances very close. I don't know if there is any operational preference between the two t.stat placements (both seem fine to me if assembled correctly).

Leeroy's Ramblings describes a procedure for tweaking the hood latch assembly to provide more space for the older motors. I've done that and it works -- but it's just as easy to pull the head cover with the attached t.stat cover. Additionally, it's better to install the older t.stat cover and gasket on a workbench IMO. I find it's important to resurface the t.stat cover like you would the head cover, then assemble with proper torque and circular bolt pattern. The lower left side of the cover was probably a trouble spot until '85 when there were two opposing bolts at the bottom of the cover. I know I had some trouble with leakage at that spot with an '83 9.9.