Originally Posted by geedee
I have a 3 cylinder 32hp Ford "Dexta" motor in my boat. it is on rubber mounts. the front mounts is a 1/2 inch thick plate bolted onto the front of the engine with lugs onto the front rubber mounts, at the rear there are mounting lugs on the bell housing.. from these lugs there are Z plates up onto the rubber mounts. My problem is on one mount where the Z plate is connected to the lug on the bell housing it has broken the 1/2" bolt off... the bolt is through the lug and threaded into the Z plate. the bolt has a plain and a spring washer.. and it breaks off just under the hexagon head of the bolt! this has happened 3 or 4 times over a 10 year period.. have had the alignment checked etc. Has anyone have any idea why this should be happening?
I have no marine
experience of this, but I do have experience with 3cyl Ford
engines and do know that they run like a 3 legged giraffe at low speeds. I think it is something to do with the asymetric geometry of a 3cyl motor. Don't get me wrong, I own two Ford tractors both of which are 3cyl motors and one of which I have owned for around 25 years. Great economical engines. Like any engine I suggest not running at any speed for extended periods where there is significant vibration. Find that sweet spot which matches the boat speed you want without the vibration. The destructive power of vibration is I think underestimated. I once set up an irrigation pump
on a big trailer
that was converted from a truck chassis, I used a 4cyl Ford 500E industrial engine (80hp?) to drive the big pump
through a triple drive belt. I got engineers to machine up a flange that bolted directly to the flywheel with a short shaft extending through the bell housing on to a large self centering bearing with a triple cast iron pulley wheel
on the external end. The shaft was at least 2" thick. The engineers assured me the set up was true and yet after a few hours the shaft separated from the flange plate. This happened i think a couple of times. Finally we decided to mount an extremely large (and expensive) rubber flexible coupling inside the bellhousing so that the engine was essentially separate from the shaft holding the pulley wheel
. Problem solved
. To further illustrate vibration problems. I had a 2000litre fuel tank
mounted on the chassis as well. The pump used to operate up to 16hrs a day and she did guzzle the fuel
like an alcoholic on steroids. I had the fuel
tanker delivering direct to the field wherever the pump was situated about once a week. Well after maybe a couple of hundred hours the vibration split the welds on the fuel tank
and ultimately I had to mount that on rubber as well.