1986 Johnson 150, bad crankcase seal between the two halves

[79Jimmy]

Hi there, so I did a full rebuild on my V6 last winter and it turned out great, except for one thing. I have a fuel/oil leak coming from between the two case halves. I thoroughly cleaned the mating surfaces before applying a thin coat of Gel Seal before mating the two. Engine ran great but this leak was very obvious and pissing me off, engine is white and I'm premixing with red XD30! Lol. Anyway, I pulled the powerhead off and split the case to see what was up and found the seal had cured and was good except for the six sections of the surface where it is quite thin (about 1/4-3/8" wide) basically where the bypass covers butt up next to it. The Gel was still intact there but it was obvious fuel was getting pass and outside of the case. Not sure how to rectify this. I didn't use any primer. The best I can come up with is to just reseal using Gel Seal II again but this time leave a 1/8" bare strip from top to bottom and put a very thin bead of Aviation form a gasket (the stick brown stuff) on that bare strip then bolt it together again... I'd love to hear any other ideas or questions..
Thanks, James

 

[emdsapmgr]

I don't see a lot of gel-seal remaining on either crankcase half. You may not have applied enough the first time. When I do a V6, I have two of the small tubes of red gel-seal and use one, plus part of the second tube in order to get full coverage. The sealant should ever slightly ooze out of the joint when fitted and torqued. Clean the surfaces with acetone, dry then apply. No need for any av gasket on this surface.

 

[racerone]

I use a 1/16" diameter bead of sealant.------Do NOT smear it on.----Install cover and never a problem.-------------------I use a fine file on both surface to look for and get rid of small imperfections and bumps.

 

[79Jimmy]

Thanks guys. When I sealed it the first time I did smear it on, fairly thin too as I thought that was the procedure. One more question, should I apply the bead to just one side or both?

 

[daselbee]

Hmmm....DO NOT use a bead. Why trust a bead to squish evenly? You cannot control the squish.

Always smear it out, leaving a light pink to medium red coloration.
I smear it evenly and lightly on both halves.

DO NOT EVER use the bead method.

 

[79Jimmy]

Well I got her back together and used quite a bit more 518 this time, a full tube plus about a quarter of another. A majority went on the cylinder side of the block particularly around the outer perimeter and the intake side got a thin layer before I married the two without much delay. Good squishout but I was careful not to get too close to the crankshaft seal rings and the middle bearing channels. I'm going to wait a few days before a test fire, hopefully this does the trick.

 

[racerone]

Been using a 1/16" bead of sealer for many , many engines and never a problems with leaks.

 

[Keitholboy]

Hi there, so I did a full rebuild on my V6 last winter and it turned out great, except for one thing. I have a fuel/oil leak coming from between the two case halves. I thoroughly cleaned the mating surfaces before applying a thin coat of Gel Seal before mating the two. Engine ran great but this leak was very obvious and pissing me off, engine is white and I'm premixing with red XD30! Lol. Anyway, I pulled the powerhead off and split the case to see what was up and found the seal had cured and was good except for the six sections of the surface where it is quite thin (about 1/4-3/8" wide) basically where the bypass covers butt up next to it. The Gel was still intact there but it was obvious fuel was getting pass and outside of the case. Not sure how to rectify this. I didn't use any primer. The best I can come up with is to just reseal using Gel Seal II again but this time leave a 1/8" bare strip from top to bottom and put a very thin bead of Aviation form a gasket (the stick brown stuff) on that bare strip then bolt it together again... I'd love to hear any other ideas or questions..
Thanks, James

Any luck?? I’m having exact same issue with mine thanks

 

[racerone]

Maybe the bypass covers are warped.----It should be easy to find / correct any leaks on the crankcase.