Is the standard Merc V-6 1.87 gear case a good choice for an 80 mph rig?

[Bumblebeeman]

I plan on putting a 200 EFI on my 1000 lb boat that will do 72 mph under ideal conditions with a Merc XR4 150. I estimate about 80 mph top speed with the 200. I have been reading Scream and Fly posts about the various high performance gear cases. But I'm wondering if the standard 1.87 gear case will work effectively at a top speed of about 80. What's the feeling among people with experience with this gear case?

[vnemous]

Depending on the hull you may get more speed if you surface your prop. You may find you need a nosecone just to keep water pressure even though you may not be near blow out speed JMO.

[FUJIMO]

I plan on putting a 200 EFI on my 1000 lb boat that will do 72 mph under ideal conditions with a Merc XR4 150. I estimate about 80 mph top speed with the 200. I have been reading Scream and Fly posts about the various high performance gear cases. But I'm wondering if the standard 1.87 gear case will work effectively at a top speed of about 80. What's the feeling among people with experience with this gear case?

No worrys. 80 mph? No problem at all.

[roadkill636]

Is your XR4 gearcase the stock 2-1 for the 150? Is it the smaller diamiter case?

Because the XR motors. Ame with smaller hub cases than the 200s and ran faster due to less diamiter bullet size.

[TraceF3]

I don't know jack about an 80 mile an hour boat but I've been running single and twin outboards for 3 decades, part-time tournament fishing where I'd have the l/u out of the water repeatedly and clip the rev limiter literally hundreds of times. Never had a l/u fail yet. I'd say yes. Go for it.

[One Oldman]

I would be afraid of blow out over 80 without a cone.

[Bumblebeeman]

In answer to RoadKill, My XR4 has the small diameter bullet 1:78:1 gear case that came on the XR4 motors.

[90 5.0]

In answer to RoadKill, My XR4 has the small diameter bullet 1:78:1 gear case that came on the XR4 motors.

1.87 is the preferred case and ratio for 99% of the 2.5/2.4 boaters out there.

You will need a larger prop than you would with the 1.78 gear case and it might be slightly faster depending on hull and set up with the narrower case.

With a 200 for longevity most would say the 1.87 200 case is a better option.

While the 1.78 case might be slightly faster I would swap it with the 200 if you do lots of running for longevity reasons.

You should be able to find someone to swap your 1.78 for a 1.87 if you don’t have one , it’s a sought after case for some racers and very light boat owners that want to run shorter props and not tear up their race cases for river runs.

I’d love to have a 1.78 case for river riding my light boat