Doug Overkill
Active Member
Hello forum,
I know this topic has been covered a lot and I have spent the week reading a bunch of the threads and still have a couple questions. Most of my questions are about peoples actual results. The issue is a very common 787 one in that the seal on the crankshaft leaks 2-stroke oil from the rotary valve gear into the bottom of the cylinder (Mag side in my case). If I run the boat everyday it is not enough of a leak to be an issue, just a little extra smoke on startup. Clearly the best answer is run the boat everyday! Unfortunately I have to go to work and live and have responsibilities and so the boat sits for several days or a couple weeks at a time. When this happens there can be enough oil in the cylinder to hydrolock the motor. As anyone who has this problem knows, remove plugs and crank until it stops spitting all over the engine bay. Remember to pause every so often so you don't cook the starter! Once most of the oil is gone, replace plugs and start her up. A bit of mosquito control later (smoking) and she runs great.
I have decided this fall/winter I would 'fix' this. So there are 4 solutions talked about on several different threads including this one:
787 crank seal leak in which @markg612 lays out these options:
1. Do it right - Replace or rebuild crankshaft and add 518 sealing the new seals in place - most expense option!
2. Split case and seal existing seals with Loctite 518 - cheapest with a bunch of labor
3. Seperate RV oil supply & vent from reservoir- replace oil with thicker lubricant so that it won't flow thru seal
3a. new lube is 80/90 gear oil or something thick
3b. oil lines get a Zerk fitting and pump this RV gear area full of grease. Such as XPS 293550010 (for driveshaft couplings)
4. Add ball valve in the supply line shut off when not in use. Remember to turn on when is!
I like option 2 the best, but it is a BUNCH of work right before snowmobile season.
#4 seems easy but I expect that a lot of oil still ends up on the wrong side of the seal as you have stopped the large supply only and whatever is in the area can still leak thru.
For those of you who have done any of these. Please post back with your results. Would you do anything different? Would you recommend this to others? For those who did #3, what lubricants did you use? Did you have any leakage that resulted in smoke or other issues? Did it survive for very long and is it still running that way. Did anyone use the zerk fitting method?
My motor is strong and has 150,155psi compression, checked today. I do not really want to replace a crankshaft on a good running motor. I also want to stop/slow the oil leak so I don't loose an hour or more on a Saturday morning pumping oil out of the cylinders cause it sat for a week.
I know this topic has been covered a lot and I have spent the week reading a bunch of the threads and still have a couple questions. Most of my questions are about peoples actual results. The issue is a very common 787 one in that the seal on the crankshaft leaks 2-stroke oil from the rotary valve gear into the bottom of the cylinder (Mag side in my case). If I run the boat everyday it is not enough of a leak to be an issue, just a little extra smoke on startup. Clearly the best answer is run the boat everyday! Unfortunately I have to go to work and live and have responsibilities and so the boat sits for several days or a couple weeks at a time. When this happens there can be enough oil in the cylinder to hydrolock the motor. As anyone who has this problem knows, remove plugs and crank until it stops spitting all over the engine bay. Remember to pause every so often so you don't cook the starter! Once most of the oil is gone, replace plugs and start her up. A bit of mosquito control later (smoking) and she runs great.
I have decided this fall/winter I would 'fix' this. So there are 4 solutions talked about on several different threads including this one:
787 crank seal leak in which @markg612 lays out these options:
1. Do it right - Replace or rebuild crankshaft and add 518 sealing the new seals in place - most expense option!
2. Split case and seal existing seals with Loctite 518 - cheapest with a bunch of labor
3. Seperate RV oil supply & vent from reservoir- replace oil with thicker lubricant so that it won't flow thru seal
3a. new lube is 80/90 gear oil or something thick
3b. oil lines get a Zerk fitting and pump this RV gear area full of grease. Such as XPS 293550010 (for driveshaft couplings)
4. Add ball valve in the supply line shut off when not in use. Remember to turn on when is!
I like option 2 the best, but it is a BUNCH of work right before snowmobile season.
#4 seems easy but I expect that a lot of oil still ends up on the wrong side of the seal as you have stopped the large supply only and whatever is in the area can still leak thru.
For those of you who have done any of these. Please post back with your results. Would you do anything different? Would you recommend this to others? For those who did #3, what lubricants did you use? Did you have any leakage that resulted in smoke or other issues? Did it survive for very long and is it still running that way. Did anyone use the zerk fitting method?
My motor is strong and has 150,155psi compression, checked today. I do not really want to replace a crankshaft on a good running motor. I also want to stop/slow the oil leak so I don't loose an hour or more on a Saturday morning pumping oil out of the cylinders cause it sat for a week.
