So I'm looking into replacing my lower unit. Found a smoking deal on a new Mercury lower unit but it has a 2.00 : 1 gear ratio instead of my factory 1.87 : 1. Anyone have any experience with this change. I think I would probably still be in my rpm range but I don't want to make my boat slower or hurt the engine. I appreciate any input.

JUSTA ?.. is your case a 4 3/4" hub?.. reason i asked is there were a few in '96 that still had tha 4 1/4" small hub???

ta answer your ?.. it (with current prop) should increase rpms a few hundred, maybe 2 ta 400 (maybe).. don't know whatcha got for rig and set up?.. whatcha turnin' what (prop) ya got now?.. you may lose a coupla mph on top but... it will pull a little stronger outta tha hole.. that motor can turn 6 ta 62 hundred all day long if your close with tha 2 ta 1...

might add anything said is just an experienced GUESS.. no two rigs will react tha same.. might be close but not necessarily tha same... jmo

if its THAT good of a price it would be worth it ta several folks if it didn't work out for ya.... jmo.

I do have the larger hub. I have a 18 foot Nitro. I have two propellers. Both are Mercury Revolution 4. One is a 23 pitch the other is a 21 pitch. Unfortunately I don't remember the RPM's I'm turning. I know I can't reach the operating range with the 23. And the 21 I think I'm 5400. But it's probably been 5-6 years since I've run this prop. So I'm unsure. I hit a rock and damaged it. I just sent it out for repairs last week. This boat has always accelerated hard out of the hole.

I think you could run it with the 23p since your rpm will increase, you may have to have some prop work done to tune it in. I don't believe the 21p was only running 5400 rpm though, maybe 6400. I had a 18.5' Nitro with an older 150 Black Max that would turn a 22p at 6200 and that prop had a deep cup in it to keep the rpm down to that. I think the 21p may blowout on the hole shot and over rev on the top end...

You might check but I believe the smaller gear case on the 2.0 requires a different prop. I know that Mercury made the Tempest in even pitches for that gear case and odd pitches for the larger one.

justa note stump.. tha only "small" (4 1/4") gearcases were on XR4 and XR6.. they were same 1.78 gears but slightly different inside and outside.. all others were large (4 3/4") no mater tha ratio.. 2.33, 2.0, or 1.87's..........

I was thinking XR6 but typed 2.0. You had already covered anyway. I hate to see the OP buy the new lower and get home and find out his prop does not fit.

yeah, i ask 'em that first thing.. tha little gear cases bring a premium with tha hot rod bunch.. 6's have a slighty larger pinion gear and bottom bearing... those were always my go to case.. a guy named Steckbauer that built a lot of 'em with cut down 2 ta 1's that were tha nuts for bad boy's.........