Engine mounts

[Leachy]

Hi,
I'm looking for advice. I have recently purchased a 22 ft wooden boat, built early 1970's. When purchased, the boat was minus it's original inboard engine. I have since acquired a Volvo MD2B. My problem: with the MD2B now positioned in correct alignment with the prop shaft, the boat engine mount stringers will not allow room for flexible engine mounts. If I bolt the engine brackets directly to the boat will the whole thing vibrate apart??!! As you know, the MD2B is a heavy lump (220kg) and not having run the engine yet, I am unsure of how smooth she is through the rev range. I am reluctant at this stage to start attempting modification of the very substantially built stringers.

 

[Peterduck]

A pal of mine has an MD2 in his boat, and I was always fairly impressed with the smoothness of it. In his case, it is a pretty old engine now, although it hasn't had a lot of use. It does have a lovely, big, heavy flywheel which smooths out what might otherwise be a roughish engine. More modern engines have smaller flywheels in the fatuous hope of faster acceleration.
Peter.

 

[Leachy]

Thanks for the info. I assume on your friends boat the MD2 was installed with flexible engine mounts? Does anyone know if this engine was designed to be used without flexible engine mounts??

 

[unclebraddah]

Not that I know much about that engine but I have found if you spend enough time on your belly getting intimate with the thing an answer will present itself. I for one would be very hesitant of modifying the stringers. Ive had on a couple occasions had to reconfigure the mount line up due to engine room changes. Ive flipped the brackets from engine to mount. Removed excessive parts to the mounts.

 

[Leachy]

I'll bite the bullet and try without the flexible engine mounts. I will soon know if the setup goes into self destruct?! If anyone is interested, I'll post the result!

 

[burgundyben]

Certainly come back and let us know.

Personally I would want them on rubber mounts.

A number of installations have a built in weak point that is meant to let go should the prop pick up a rope.

Volvo 2000 series were installed in Westerlies in that manner, the engine mounts were designed to let go.

On my Perkins the front end of the shaft is in a clamped hub with no woodruff key so if needs be it can spin.

 

[Saddletramp]

My MD2b vibrates up to around 800 rpm after that it is fine.
As it ticks over at around 500 it may be be a problem for you.

I think you would be wise to run it out of the the boat to see for yourself.

One option would be to look into altering the brackets on the engine or making some more up to suit.

As you know it is a heavy engine, I have mounted mine on large hardwood bearers about 4" wide.