Crankcase Bolts Broken - Ruggerini Motor

[Eero Gaffney]

I bought the Mooie Mina in Zeeland, Netherlands August last year. It came with an inborn 2 cylinder Ruggerini motor (model mm150). I then motored it up to Lauwersoog over the course of 5 days total. At the end of the fifth day, the engine broke down unexpectedly. Before that it had been running fairly smoothly for the majority of the journey, although in neutral and when not warm on low RPM it would vibrate significantly. I had a mechanic diagnose the problem who said that the flywheel had become disconnected from the crankshaft. I brought the boat to his workshop and he took the engine out. He found that the four bolts connecting the flywheel to the crankcase had broken off and the seal of the crankcase had also broken. The mechanic drilled out the old bolts and thought that although the thread at the start of the crankcase was slightly damaged, deeper in it was strong enough to hold new bolts no problem. He put new original bolts in and a new seal to the crankcase. The engine at that point did not run well yet (too much shaking). He then replaced the fuel-hoses and pump-ball. Additionally he took out the injectors and cleaned them. He also replaced the old front mounts with new ones. After all that work the engine ran well again also on low RPM without much shaking. I proceeded to bring the boat back to Groningen where I kept it over the winter. Last few weeks I did some maintenance on it and then set off towards the Ijsselmeer. I only made it 13km out of the city before it broke down again. Before It broke down it had sounded great without much shaking at all. After breaking down I did a quick diagnostic again and it seems to be exactly the same problem as before. When I start the engine it makes a lot of noise with the flywheel spinning but the crankshaft not moving at all. When put in forward gear the propeller does move slowly but the crankshaft still won’t. After starting the ignition I can no longer manually stop the engine, the flywheel continues whirring for a while before it slowly fades and shuts off. I am wondering if anyone can help me diagnose the problem. Part of the issue the previous mechanic thought may be causing the initial break in addition to the shaking was some sort of misalignment of the engine but he made sure to align it properly when putting it in again. Could there be some internal misalignment somewhere still causing this or possibly the old thread not holding the new bolts well? I would like to fix the engine but of course don’t want to do so unless I can be sure this problem won’t occur again.

 

[179580]

What you are reporting is impossible. You say the prop is turning but the crankshaft is not?

 

[Caraway]

Perhaps we are having some language problems here. The OP has said crankcase when I am sure he means crankshaft.
It looks like there is a rolled pin in the 5th hole in the crankshaft flange which I am sure should really be a dowel to prevent slogger between the crank and the flywheel.
That may be what is working the bolts loose. They should also have been fitted with locktight or similar.
The seal is the crankshaft rear oil seal.
I'm not quite sure what the mention of the prop turning relates to. Is the engine actually running? In which case the crank is turning, but not the flywheel, not at engine speed anyway. I think the flywheel is spinning courtesy of drag from the crankflange, but incapable of spinning at crank speed. Presumably the flywheel is held in place courtesy of the splined gearbox input shaft.

Sounds like the bolts are not the correct ones, not correctly fitted and there is a tight-fitting dowel missing, probably replaced with a rolled pin which has also sheared.

 

[Boater Sam]

Where has the locating dowel gone? It should be a hardened solid steel dowel tight fitting in both the crank and flywheel. Not a hollow roll pin.

The bolts must be high tensile, locked with Loctite and possibly a tab washer as well.