View Full Version : Possible to remove & install crankshaft without removing pistons?

04-15-2010, 09:07 AM
I have a small oil leak on the rear main seal because of a groove in the crankshaft, I might go for a engine overhaul next winter, it's an old engine with almost 1800 hours, but I'll probably still want to overhaul it just for learning/fun;-) Anyway, does anybody know if it's possible to replace the crankshaft without removing heads and pistons?

04-15-2010, 09:32 AM
you certainly can do this, drop the oil pan, unbolt rods and mains, drop and crank and replace. people do it all the time in cars, with the engine still in the car. but i'm sure there isn;t enough space to do this in a boat. pull the engine and put it on a stand, then you can turn the engine over and work on the crank on the "top" instead of upside down. be super careful when reinstalling the crank with all the bearing surfaces and all those sharp rod bolts stick out (put some small pieces of fuel line over them to cover the threads, do this right after you take the rod ends off)

04-15-2010, 03:55 PM
Thanks, I would offcourse take the engine out of the boat, very simple on a prostar;-) I guess the engine should maybee have a total rebuild when I first go for such a project. For this summer it will be a little bit of oil in the bilge, old boat, I can live with that;-)( new rear main seal but didn't help very much).

04-15-2010, 04:08 PM
How sure are you that you installed the rear main seal without nicking it? I have managed to screw up a seal or two during installation over the years. Might try another stab at replacing the seal.

04-15-2010, 06:13 PM
I changed it last spring, no luck. Changed it again now, no luck. It's a pretty big groove in the crank. BUT: http://www.microsleeve.com/tech.html . Why didn't I find out about repair sleeves before I put the motor together this time, damn! ;-))) Tempted to take the boat out of the water and try this sleeve. Anybody tried these sleeves?

04-16-2010, 03:36 AM
You can replace crank without tearing down the rest of the engine. Make sure you keep your rod caps and your main caps in the right order. Replace your main and rod bearings before you put it back together. All of the caps have got to go back in the same order they came off. I personally lay the caps on the bench with the bolts still in the end caps. I also make sure that each rod bolt goes back into each hole it came out of and the same with the main caps. Do not mix anything up. Drop in a new front and rear seal and drop that baby back in. Before you take the engine out do a compression test and a leak down test to see what kind of shape the engine is in before. You may not need to do the rest of it. I personally would not take it out twice. Rebuild it all now and forget about it if it needs it.

04-16-2010, 03:45 AM
Thanks! Still tempted to try that sleeve tho, they claim that you can still use the standard rear main seal after the sleeve is on(doesn't change the sealing OD of the shaft much)

04-16-2010, 03:54 AM
I assume that you can put the sleeve in while the engine is still in the boat.

I bet that would work and be a cheeper fix. If it doesnt all you wasted was a couple of bucks and a little time.

I would replace the seal as well again while you are that far down.

04-16-2010, 04:05 AM
Yup! Hard/impossible to get the seal out without damaging it, so it has to be replaced.