changing a crankshaft 1989 Mercury 70

[swimmin' for shore]

I don't usually tear quite this deep into a motor, but I bring theim in as blown motors sometimes and part the motor. In this case, I brought in a 70 HP Mercury that was "blown". It isn't blown, though. The Crankshaft top wheel was broken. The cylinder walls look like new, as did the old pistons and connecting rods.

I took the crankshaft out and pulled out another 3 cylinder crankshaft from another motor I had that had been blown. The pistons and connecting rods were off of that one, so I took the original pistons and rods-all 3 of which looked like brand new, and attached them to the good crankshaft.

Everything was put back together. Everything looked good. The problem now is that the motor is really, really tight. It turns but cranks incredibly hard. Same block and same pistons, but now it is turning over harder than heck. Any suggestions?

 

[turbinedoctor]

Re: changing a crankshaft 1989 Mercury 70

Hey swimmer, Sorry to hear about your tight engine. I have a couple of questions about it. 1) What do you mean by the crank top wheel was broken? I am unfamilar with the term WHEEL when talking about crankshafts. A picture or two would help explain this. 2) Did you ever crank this engine over with the original crankshaft? 3) Is the replacement crankshaft from the same model engine as this one?

I don't have a ton of experience with rebuilds but I am completing one now and can say that mine does turn over harder after the rebuild then before.


Durwood

 

[Faztbullet]

Re: changing a crankshaft 1989 Mercury 70

The 3 cylinder Merc had 2 different crankshafts, the difference's are:
1) 1987-91 had bottom guided rods
2) 1992-03 had top guided rods
3) the 493-827616A1 had a 1-2-3 firing order
4) the 493-827616T1 had a 1-3-2 firing order

It sounds to me like you missed a bearing dowel pin on a center main bearing.