Reassembly questions after piston replacement on 15HP M15B2

[rookieboaterj]

My tohatsu m15B2 started having compression issues a couple of months ago. I did a test, and came back with bad compression on my top cylinder.
I ordered gaskets for the exhaust, intake, and head, but was unable to find anywhere on the diagram, a gasket that goes between the block and the lower rest of the motor.

So, i took the carb off, removed the throttle linkage, disconnected the shifter starter block thing, and finally the 4 large 13mm bolts holding the block to the bottom of the cowling/shaft. This is the key part here... after seperating the block from the driveshaft housing, i noticed what looked like parts of a gasket. on the diagram, however, i am unable to find a gasket that goes there, and there is a knock there, similar to the crankshaft housing knocks, which leads me to believe there isnt a gasket there.

When i reasssembled after fixing my burnt piston and shattered upper main bearing, i kept the old gaskets in, and started. water comes gushing out between where the block and driveshaft housing meet, the spot where i saw parts of gasket, but see no gasket on the diagram. as i continued to tighten the 4 bolts, i noticed the leak starting to diminish. the rings are seating nicely on the piston, and the motor sounds a hell of a lot better then it did before.

Next, i disassembled again, and have scraped all the gaskets off, and are giving all parts a thorough cleaning. i intend to reassemble with the new gaskets i have. So..... that is where i am at now.

Should i be greasing the upper and lower oil seals on the crankshaft?

Should i be putting some sort of grease or lube oil material anywhere in there?

i guess what im asking is.... does anyone have any advice on the best and most long lasting method for reassembly would be?

i plan to take them to a shop to have the bolts torqued to spec after i get new gaskets lined up....

thanks for your advice in advance...

josh

 

[Sea Rider]

There must be a base gasket between lower crankcase and upper pan for water and exhaust not to drain from there.Clean both metal mating surfaces, apply a light coat of megagray silicone at both sides of gasket, sit crankcase and torque tight lower 4 bolts.

Code is 350013031 Engine Base Gasket, check Iboats or any Tohatsu dealer,

Upper and lower seals of crankshaft are not required to be greased when assembling.

Happy Boating

 

[rookieboaterj]

Indeed. I used some gasket material and cut it to shape using a printout of a picture of the gasket and marked it and was able to cut it out to fit perfectly. No more leaks, motor sounds so much better. Doing the break in according to tohatsus website with double oil ratio. Did the 10 minutes idle, and about 1 hour under 1/4 throttle, and its running very smoothly. Sounds like a completely different motor now. There was a distinct clicking before, that is gone now. It also idles MUCH smoother, and is able to troll very efficiently. Im amazed i was able to fix this.

Thanks for all your help iboats forum, on this thread and my other thread as well.

Thank you SOO much!

Josh

PS. I'll be ordering the new base gasket probably tomorrow. The gasket i made is just as good, and if it doesnt work for long, i'll have a original spare.

 

[Sea Rider]

The original one is a realtive thin 2 sided black coating with an interior alum sheet in middle, much better than making gaskets with gasket sheets.

Happy Boating