3.0 liter Merc...cam not turning.

[Skid-joe]

Hello all,

Thundercraft 16 ft, 3.0 liter mercruiser 88.

This week, the engine died at speed.....

Back at the dock, no compression on ALL cylinders, and rotor in distributor not turning.
So timing gears must have broken......


Question,
On these engines, will the pistons strike the valves in this condition,

and from what I have seen on parts diagrahm there is no timing chain....JUST gears, is this the case.

thanks for any replies,
Joe.

 

[winterfunguy]

Re: 3.0 liter Merc...cam not turning.

Correct the timing is handled by gears in these engines ( generally a plastic called phenolic) they are not an interference motor so the valves should be fine. I would still pull the sparkplugs and take a peek in he bores to check the pistons for contact marks with a bore scope. If the cam had 1 valve at max lift when the piston came up it could contact the piston slightly, this is highly unlikely but better to know than just assume. Good luck...

 

[Skid-joe]

Re: 3.0 liter Merc...cam not turning.

Thanks Winter...

going to pull the boat out and open-up the engine....

Wish me luck,
Joe.

 

[fishrdan]

Re: 3.0 liter Merc...cam not turning.

Pull the distributor and see if the cam is turning when the engine is cranked over. The pin on the dist gear could have sheared off or broken in half and fallen out, causing the rotor to stop turning. If the cam gear stripped out, I think you will have bent valves.