Engine beds not in line with propellor shaft.

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zeehond

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This may seem very strange to all you practical guys out there but It seems the engine beds on my 1992 Warrior 40 are not correctly aligned with the propshaft - a misalignment of 9 degrees. The beds are parallel to the waterline and the shaft is inclined downwards at a 9 degree angle towards the stern. This means the mounts are seriously deformed as the back end of the mount is metal to metal.When I bought the boat, 7 years ago, the survey did not mention this.
I had the mounts replaced 6 years ago; the mechanic said the back of the mounts " might" hit the fixing bolts and I should consider using a Dremel mini-grinder to take away the lower rear end part of the metal of the mount to prevent this occurring. He did not say the beds were the problem. I did not do this as it was downplayed, not critical.
Earlier this year,, a survey highlighted this issue, saying that action needed to be taken as metal was/is being worn away at the back end of the deformed mount. In fact, we have lifted the boat as we have no confidence in the installation.
My thoughts now are how to correct this. 1) Remove the engine and redo the beds. Obviousl the ultimate solution but to remove the engine from its central position in the saloon is daunting. 2) Remove the engine brackets sequentially with the engine in place and cut and weld in the correct shape. Once remade reconnect them to the engine in such a way as to allow the mounts to be properly installed 3) Remove the engine brackets and mounts and do as good a job on the beds as limited access allows (again sequentially with the engine remaining in place) Glass-in a wedge of hardwood 1:11 (9 degrees).
Any thoughts/advice on this will be welcome. The engine is a Perkins M60 with Hurth 250 g.box and weighs just under 300kilos I believe.
 
Most Hurth gearboxes have an 8 degree down-angle. It may be that someone replaced the box on your boat with a straight gearbox, causing the problem.

If this is the case and you want to swap the gearbox out for a down-angle box (which is probably the best idea), I have a Hurth ZF25 with down-angle in my garage that I removed earlier this year from a Perkins Prima when I re-powered the boat, so it will fit straight on as a direct replacement. Let me know if you are interested and we can discuss a sensible price for you.
 
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If your engine beds are parallel to the waterline, you will need a down-angle gearbox. Trying to get the engine up to the right angle in the front will cause problems with oil levels and feeding up from the sump, and potentially water flow through the engine.
 
zeehond said:
My thoughts now are how to correct this. 3) Remove the engine brackets and mounts and do as good a job on the beds as limited access allows (again sequentially with the engine remaining in place) Glass-in a wedge of hardwood 1:11 (9 degrees).
Any thoughts/advice on this will be welcome. The engine is a Perkins M60 with Hurth 250 g.box and weighs just under 300kilos I believe.
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Most marine engines will tolerate longtudinal tilt, Beta quote up to 15 deg. for example. I would favour modifying the beds if that doesn't put the coupling height out too much. Incidentally, 9 deg. is 1:6
 
earlybird said:
Most marine engines will tolerate longtudinal tilt, Beta quote up to 15 deg. for example. I would favour modifying the beds if that doesn't put the coupling height out too much. Incidentally, 9 deg. is 1:6
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Really? You would go to all that trouble when you could just replace the gearbox for a couple of hundred quid or put a CV coupling in?
 
Bobc said:
Really? You would go to all that trouble when you could just replace the gearbox for a couple of hundred quid or put a CV coupling in?
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£200 isn't bad but a new 'box must be a great deal more. A CV coupling and thrust bearing, if it fits, could also be pricey and 9 deg. angle is quite a lot, some only take 4-5 deg. per joint, and that with power de-rating.
 
Bobc said:
Really? You would go to all that trouble when you could just replace the gearbox for a couple of hundred quid or put a CV coupling in?
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Fitting an Aquadrive is well worth doing, although not certain that it can accommodate 9 degrees of misalignment. It is by no means a cheap or quick fix, mine took me a good few weekends and much measurement and pattern making. The account is on the website.
 
Am I missing something here?

All you need to do is chock the engine under the sump, remove the metal brackets that go between the engine bock and your mounts and have them cut / refabricated so that they are parallel to the top of your engine beds. Then at rest, your mount will not be deformed.

Sure enough it will deform slightly under load but no more so than a level engine and down drive box.

Very few yachts seem to have the utopia of all mounts and beds exactly parallel to and on the thrust line of the transmission.
 
Thanks for all the good ideas, guys. Will probably need to modify the beds which are hardwood glassed-in with coach bolts as fixings. Should be able to remove brackets/mounts from each corner sequentially and have space enough to make the alteration.
Failing that could cut and weld the bracket to match the angle?
 
Bobc said:
If your engine beds are parallel to the waterline, you will need a down-angle gearbox. Trying to get the engine up to the right angle in the front will cause problems with oil levels and feeding up from the sump, and potentially water flow through the engine.
Click to expand...

Is it that critical when the engine runs at all peculiar inclinations when at sea? And often a lot more than 9deg. Does the engine oil pump normally lose suction when going up or down a large swell. Maybe it will mean the oil dipstick will need re-calibrating/marking.
 
FWIW my Centaurs bearers bore no relation to where the shaft exited the hull. 10 minutes pinging laser lines all over the place and a day with a disc cutter and grinder sorted the problem. Made a jig to the dims of the new lump i fitted and now everything lines through,...................... they don't make them like they used to.
 
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