Allison GrandSport with Merc 150ProXs four stroke needs a gear change. Anybody try?

[OceanMarine]

Ya, the four cylinder is smooth and powerful for it's size and not too heavy. Great engine overall. Bullet proof. Sounds decent from the shore too. Quiet when cruising. The ProXS version revs 200 more RPM, has stiffer lower mounts and the 4.88" gearcase with 2.08:1 gears. The Pro dynos at 163 HP, the regular 158 HP.

Mine was the regular 150 with ProXS mounts and a coned lower, 1.92 gears. If Brandon puts the 1.85 gears (from the Verado 4cyl 4.88") He'll probably be able to be in the 82-83 range. Mine was setup conservatively and would run 80 MPH with a 30" Promax.

Low 80's is the goal plus swinging a small prop to be more efficient, less paddlewheel effect and better handling.

So the part numbers of the case housing between the 150proxs and the 200-275 verado 4.8 are different. But likely due to paint color. I have been able to cross reference carriers and shim sets and other parts and they appear to be identical so that should in theory mean they are essentially the same case

The carrier for example is shared and is 8m0083392 and the housing number i found was 2B026817 for those verados and the 1.85 forward gearset is 892595A05

Getting closer. Ive been in contact with a few very helpful people here on Long Island. Hoping to check the availability and swap these gears out soon.

[JR IN JAX]

Jeff Ziemer has the best balanced Grandsport I know of.

[Ziemer]

Jeff Ziemer has the best balanced Grandsport I know of.

"had"

I sold it a month or so ago.

[OceanMarine]

Just wanted to update this thread in case anybody wants to do this out there. The Verado 4.8 case for 200-275s of the past gear swap does work for the new Mercury 150ProXs four stroke. Thanks to a great local mechanic (Eric) the 1.85's went in without a hitch. Testing the new gears tomorrow and very excited!

[David]

My brother is thinking of buying the same rig, good info, thanks

[transomstand]

Just wanted to update this thread in case anybody wants to do this out there. The Verado 4.8 case for 200-275s of the past gear swap does work for the new Mercury 150ProXs four stroke. Thanks to a great local mechanic (Eric) the 1.85's went in without a hitch. Testing the new gears tomorrow and very excited!

How does the ECU deal with the gear change?

[OceanMarine]

How does the ECU deal with the gear change?

Ill keep you guy posted but i dont think ill have any issues. The stock 150 has 1.92 gears, the Proxs makes at least 5hp more then the regular 150 and supposedly more torque with the spark advance tech it has, so i dont think there should be any issue with the 1.85. I know somebody else did 1.75's without issue. I assume ill gain a couple of MPH hopefully, but even better, now I wont have to swing big props and have a better handling more efficient boat going from a 32 pitch to now able to utilize likely around 28 pitch props.