29 H&h Repower

[chrisp]

I am in need of a repower for my H&H from gas to diesel, I am on the South Shore in Mass. Is there anyone you guys can recommend who could do this in the area? I don't know were to start with this , Boat has a 1.75 shaft and a zf 63a gear (2.5 to 1) with a 22x20 prop. The 454 is 47" long with the gear and there is not much room to spare.I would prefer not to have to shorten the shaft if I Don't have to. Thanks

 

[captainlarry84]

For starters your 1.75 shafting is half the work, so that is already done. Next would be a diesel power motor of anywhere from 300 - 350 HP. I would drop to a 2:0 220 A gear and chose a diesel with an RPM range of 2600 - 2800 RPMs.

 

[Fouraces59]

Steve's Shop in Charlestown. Boat can be hauled at ramp next to his shop and be put inside. He is a Deere and Lugger Dealer. Does lots of commercial work and can fabricate most parts if needed. Also will come to you.

 

[BillD]

Here ya go. 7.4 liter

Ilmor MV8 7.4L — Ilmor Engineering

 

[steveinak]

Here ya go. 7.4 liter

Ilmor MV8 7.4L — Ilmor Engineering

Wow thats a pretty looking time bomb

 

[BillD]

Wow thats a pretty looking time bomb

My Ilmor post was "informational only" One can only imagine the $price$ tag !!!

Back to this 29 H&H repower, a Cummins 6BTA 370 would be a super nice "relatively" inexpensive package.

 

[captainlarry84]

My Ilmor post was "informational only" One can only imagine the $price$ tag !!!

Back to this 29 H&H repower, a Cummins 6BTA 370 would be a super nice "relatively" inexpensive package.

Good choice for power I believe that the motor makes 370 HP @ 2800 RPMs so with a 2:0 gear your would turn a 23 X 23 or at 22 X 24. Your shafting is well within that power range. I very fine package. If you dropped at a 1.77 gear you could most likely use the 22 X 20. However I would not go that route. Lastly a 2.5 gear with that motor would come in at about a 23 X 26 or a 22 X 27 which would be too much wheel to feed water to. The 2:0 & 23 X 23 is my choice as the perfect power package.

 

[BillD]

Good choice for power I believe that the motor makes 370 HP @ 2800 RPMs so with a 2:0 gear your would turn a 23 X 23 or at 22 X 24. Your shafting is well within that power range. I very fine package. If you dropped at a 1.77 gear you could most likely use the 22 X 20. However I would not go that route. Lastly a 2.5 gear with that motor would come in at about a 23 X 26 or a 22 X 27 which would be too much wheel to feed water to. The 2:0 & 23 X 23 is my choice as the perfect power package.

Larry, the 6BTA 370 makes 370 hp @ 3000 rpm. Engine should be propped to 3150 with the boat heavy as the owner would ever run it.

Cruise 2600 when conditions permit as you want.

 

[chrisp]

The 370 is long i would have to cut the shaft and rekey it,do you think the 325 yanmar would fit without removing the shaft and what about the shaft angle with the diesel over the 454? Thanks !!

 

[captainlarry84]

Larry, the 6BTA 370 makes 370 hp @ 3000 rpm. Engine should be propped to 3150 with the boat heavy as the owner would ever run it.

Cruise 2600 when conditions permit as you want.

With the additional RPMs @ 3150 the 2:0 gear would then be wheeled at
23 X 21 or a 22 X 22. Still a great package. Hard to call which well I always like the extra diameter. But a 22 X 22 is square and if the 22 works good know then maybe stick with that size.

 

[chrisp]

If I put a 315 Yanmar in ,what size exhaust hose will I need.
If i put in the 260 hp what size exh hose would be needed , the 260 seems like a good fit I could use the same gear and prop.and should give me a 17 kt cruise.

 

[captainlarry84]

Both the 260 & 315 Yanmar have the same footprint as a 454. You also need to consider shaft angle when installing a larger length motor.
Also both the 315 & 260 will marry up to your current 63A gear.
Therefore it is most likely that you can use the same rear transmission motor mounts which is the hard part of the repower.
Both motors turn up 3800 RPMs. So your wheel size with both motors would increase in pitch only. If I had to guess without any math for the 260 Yanmar a 22 x19 for the 315 a 22 X 22.
Lastly your exhaust for both is a 4". The Yanmar repower is by far the cheapest as you can use a lot of your original equipment, if you can find one.

 

[chrisp]

Thank you larry

 

[djmarchand]

One point that has not been addressed in this thread is engine height. If you already have an engine box, then height is not a problem- you can easily add another inch or two if necessary.

But if you are trying to keep a flat sole then engine height matters a lot. Most of the engines discussed so far have more height than a V-8. One of the few engines that has the same height is the discontinued Yanmar 4LH.

David

 

[captainlarry84]

One point that has not been addressed in this thread is engine height. If you already have an engine box, then height is not a problem- you can easily add another inch or two if necessary.

But if you are trying to keep a flat sole then engine height matters a lot. Most of the engines discussed so far have more height than a V-8. One of the few engines that has the same height is the discontinued Yanmar 4LH.

David

If memory serves me correctly with the footprint of the 260 & 315 being the same as the 454, the height is no higher than the 240 Yanmar. The Cummins I have no Intel on the height.
On a repower we did in a 30' Tiara we removed 350 cu inch gas & re used the 63a gears the height was the same. A second Tiara was also done removing the same power and putting in 260 Yanmars & the 63a gear the height was also not an issue.
As stated earlier the Yanmar is the easier install, just make sure that you have enough room up front to service the timing belt on the motor. The Yanmar also weighs the same as the 454.