Wrong outdrive gear ratio

[dlogvine]

My friend is using a wrong gear ratio outdrive on his boat. He has 1.83 gear ratio which is for 4.3l v6 engine but his engine is 3.0l. I told him it is not a good combination. But I want to know for myself How damaging is this setup for the engine and the outdrive. Thank you

 

[QBhoy]

Hi
i haven’t looked it up to be fair, but I’m almost certain you can get a couple of options with these. Certainly there are at least two ratios available for the 4.3 and 5.0 etc.
depending on what boat he has with the 3.0...I’m almost sure he will be just fine with suitably pitched prop. I agree most 3.0 may have a 2-1 ratio, but I’d guess there might be some with a 1.8. As long as he isn’t loading up the engine too much, as you’ll know. He will be ok I think.

 

[alldodge]

It depends on the boat (size and weight) but so long as the motor can reach WOT rpm there shouldn't be a problem.

 

[Scott06]

Just needs to be proped to hit correct wot rpm. From my own experince re powering a 4.3 with a 5.0, keeping the V6 ratio1.81 vs 1.62 for a 5.0) just steeping up 2" in pitch kept rpms right where they need to be. I see no reason he shouldn't be able to go down 2" in pitch and get his rpm back up.

Bottom line as long as the engine can get into the proper wot rpm range it doesn't care what drive ratio is behind it.

 

[QBhoy]

Just needs to be proped to hit correct wot rpm. From my own experince re powering a 4.3 with a 5.0, keeping the V6 ratio1.81 vs 1.62 for a 5.0) just steeping up 2" in pitch kept rpms right where they need to be. I see no reason he shouldn't be able to go down 2" in pitch and get his rpm back up.

Bottom line as long as the engine can get into the proper wot rpm range it doesn't care what drive ratio is behind it.

Totally agree.

my V8 mpi runs an alpha through a 1.47, but there are the same engines running through a 1.62

 

[dlogvine]

Thank you guys

 

[Scott06]

Totally agree.

my V8 mpi runs an alpha through a 1.47, but there are the same engines running through a 1.62

Correct my buddy's 20 ft four winns with a 5.0 mpi came with a 1.62 drive probably a bit heavier and beamier boat than u run. My Sea Ray 200 sport was offered with the following combos new -
4.3 carb 190 hp - 1.81
4.3 mpi 220 hp-1.62
5.0 carb 220 hp -1.62
5.0 mpi 260 hp- 1.62

another buddy has a much lighter Tahoe Q4 with 4.3/190 hp carbed motor, 1.81 drive, but came equipped with a 23" pitch. Seems like drive ratios are designed to work with typical pitch increments , one drive ratio step is somewhat equivalent to 2" in pitch. Would make sense and allow people to run all different combos of boat and engines within the typical 17"-21" pitch range. Not sure if you can prop around multiple ratio steps but would surely be fine for one step as you outline based on what I experienced.

 

[mrzooom]

Totally agree.

my V8 mpi runs an alpha through a 1.47, but there are the same engines running through a 1.62

What diam & pitch prop are you running on the above V8?

 

[QBhoy]

What diam & pitch prop are you running on the above V8?

20” enertia 3 blade usually. But it’s a performance hull with steps and pad. Will run a 21” to about 67 mph gps if it’s very light but terrible down low. 19” tempest plus 3 blade for water sports but will hit the limiter with that easy. Usually set up to run early to mid 60’s with 20” though. Bit of an unusual example of things though.