Hypothetical question: installing a duoprop on a AQ125B/275-gctid805844

[Guest]

So....i have an opportunity to acquire a 290 DP lower with 2.30 gearing at pretty much no cost other than my labor to remove it.

I've done my googling and haven't found a single reference to anyone putting these on a boat with an AQ125B (or other VP 4-banger).

The question is, would it be worth the effort? Thought I'd give the brain trust a shot at this.

thanks,

Jim

[2850Bounty]

The 2.30:1 would be the correct reduction.

If you are able to pick it up at no charge, and it only costs you your labor, O-rings and a few new shims. ....... you don't have much to lose by trying it .

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[Guest]

Thanks Rick, I was waiting for your reply.

[2850Bounty]

The swap is relatively simple.

You'll want to learn how to take the A and B measurements and to do the math for the NEW shim pack value.

The gear oil now changes from 30W Engine oil, to GL-5 gear lube.

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[pmhinpc]

Volvo's stance on this was that the 4 cylinders didn't have enough torque to take advantage of the DP lower unit. They never offered for sale a 4 cylinder with a DP. Not even their top of the line 4 cylinder the 171. The 2.30 was intended for gas V-6 and small diesel. They never offered a gear ratio for use with the 4 cylinders. With that being said, I would have to agree with Rick in that you don't have much to loose by trying the swap. If props come with the lower, I doubt very seriously that they would be appropriate for your use. I would think that you would need a very small prop set, B1 or B2, judging by the size of your boat. If it didn't work out, you could always sell the lower and recoup the money that you put out. I for one, would be very interested in whether this would work or not!

[2850Bounty]

"pmhinpc" post=806122 wrote:
Volvo's stance on this was that the 4 cylinders didn't have enough torque to take advantage of the DP lower unit. They never offered for sale a 4 cylinder with a DP. Not even their top of the line 4 cylinder the 171. The 2.30 was intended for gas V-6 and small diesel. They never offered a gear ratio for use with the 4 cylinders. With that being said, I would have to agree with Rick in that you don't have much to loose by trying the swap. If props come with the lower, I doubt very seriously that they would be appropriate for your use. I would think that you would need a very small prop set, B1 or B2, judging by the size of your boat. If it didn't work out, you could always sell the lower and recoup the money that you put out. I for one, would be very interested in whether this would work or not!

[color]#000088 wrote:
You are correct..... the Duo Prop was not used on the OHC 4s. However, if a person was to try one, the only ratio that would be suitable would be the 2.30:1.

BTW, due to the fewer numbers of applications, a good used 2.30:1 DP lower unit is the least expensive to purchase.

It also offers the least stout gear set due to the smaller size of the drive gear relative to the two driven gears.

The E drives (for the smaller diesel engines) used a further reduction transmission that allowed the use of the 1.95:1 gear set (a stronger gear set) in order to come up with a final reduction of near 2.30:1. Be careful if/when mixing/matching E drive components.

Question: how were you able to mate a SP-C transmission to the 280 PT Intermediate housing?

If I recall, the SP-C transmission uses the large driven gear bearing.

The 280 Intermediate housing will not accept this larger bearing!

Just curious!

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