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My son is replacing the huge Perkins in his Springer with a cute little Bukh (D8?). He wants to mount it backwards above the propshaft with a belt drive.

 

so questions;

 

Has anyone done this or seen it done, what did they use as a tensioner? What pratfalls exist?

 

Does anyone know which handed an old perkins 3 pot would be? (the engine is long gone and didn't go anyway) and the Bukh?

 

Any Bukh manuals around? or means of identifying the model?

 

He has a Hurth 100-2R gearbox, am I right that it would not be a good idea to run this continuously in reverse? Does the 2 refer to 2:1 reduction?

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He has a Hurth 100-2R gearbox, am I right that it would not be a good idea to run this continuously in reverse? Does the 2 refer to 2:1 reduction?

Correct, running in reverse for long periods is bad. The ZF marine website has the duty ratings for each direction - Clicky The ZF 10 is the new name for the old Hurth 100.

Correct, the 2 means 2:1ish reduction. They normally have a plate that has A=X.XX and B=X.XX 'A' being the forward reduction ratio and 'B' being reverse reduction ratio.

 

The R indicates right handed. I can't recall whether this means righthanded prop or right handed engine rotation but it is the most common. Some old Petters for example were left handed.

Edited by Chris M
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My son is replacing the huge Perkins in his Springer with a cute little Bukh (D8?). He wants to mount it backwards above the propshaft with a belt drive.

 

so questions;

 

Has anyone done this or seen it done, what did they use as a tensioner? What pratfalls exist?

 

Does anyone know which handed an old perkins 3 pot would be? (the engine is long gone and didn't go anyway) and the Bukh?

 

Any Bukh manuals around? or means of identifying the model?

 

He has a Hurth 100-2R gearbox, am I right that it would not be a good idea to run this continuously in reverse? Does the 2 refer to 2:1 reduction?

perkins anti clockwise at flywheel end

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If it's a Perkins D3 in your sons boat then when stood looking at the flywheel with the oil filter on the left, fuel pump on the right, it goes clockwise...

 

Don't quote me on this though, but I am 99% sure.

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Hi we have a perkins 3hd46 in the boat and the rotation is , looking at the flywheel, anti clockwise.

 

we had a previous boat, albeit a small one 24 ft, with the set up you are looking at. it had a yanmar 1gm10 sitting above the propshaft, with a "deepsea"type seal cos the stern gland is a bugger to get at with this set up, driving the prop shaft thru a duplex chain running in an enclosed case with a small amount of oil in the bottom to lubricate the chain via splash. and a spring loaded tensioner on the chaincase. It worked quite well, it was designed and built by the previous owner who was a toolmaker for cosworth F1. I have also seen a similar set up using a 3cyl vetus using tripple v belt drive but this always had a lot of slip and was difficult to keep the belt pulleys in line, I think it would work better with a flat toothed belt which nowadays come in allsizes.

 

HTH

 

Paul Morris

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Many thanks for all replies, i shall post the progress as i think it's an interesting project. We were thinking that a toothed belt (think Harley Davidson) would be a little better at absorbing shock that a chain though possibly more expensive than, for instance using a small motorcycle primary duplex chain set-up.

 

The stern gland is accessible under the engine or, possibly by having the engine a little further forward than the stern gland, although you gain much less space this way. Looking at the space it does seem a very good way of mounting an engine in a small boat. The previous incarnation had a 3 cyl Perkins sat right in the middle of the boat. With a starter motor that regularly stripped its worm gear (at £200 a pop) because the mounting straps were a bit mickey mouse and didn't keep it straight.

 

It does seem like the Perkins and the Bukh rotate the same way so a new propellor is called for.

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It does seem like the Perkins and the Bukh rotate the same way so a new propellor is called for.

 

I'm assuming you are replacing a conventional engine and hurth gearbox setup.

Bear in mind that the hurth box reverses the direction of the propshaft when in forward gear (pos A).

Turning an engine around and driving the propshaft direct with a belt and pulleys will not require a prop change!

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I'm assuming you are replacing a conventional engine and hurth gearbox setup.

Bear in mind that the hurth box reverses the direction of the propshaft when in forward gear (pos A).

Turning an engine around and driving the propshaft direct with a belt and pulleys will not require a prop change!

 

I knew i was going to get confused!

 

I don't know what box the Perkins had, I kind of assumed all gearboxes reversed the rotation in forward, so no change there?

 

Look like we're going to have to try and it and see if the boat goes backwards!

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