5.7V8 with a 1.84 alpha one gear ratio

[Dmoneyone1]

I have a 2003 23' maxum with a 5.7v8 and a alpha one drive with a 1.84 gear ratio, my question is will I be ok with that ratio as i know that the 5.7 goes with a 1.47 ratio drive, if i am good to use it I imagine ill have to prop up, anyone know how hi of pitch I need to go?

 

[bman440440]

I have a 20' maxum with a 4.3 v6 (mildly warmed over)and 1.84 drive and I run a 21" 4 blade aluminum prop... and light load I get 4950 and heavy load I get 4600... have you had it in the water with a 1.47/1.62 (some v8's had a 1.62) drive? if so what was the pitch on the prop then? my best guess you are going to have to go up at least 2" in pitch.

 

[Bondo]

I have a 2003 23' maxum with a 5.7v8 and a alpha one drive with a 1.84 gear ratio, my question is will I be ok with that ratio as i know that the 5.7 goes with a 1.47 ratio drive, if i am good to use it I imagine ill have to prop up, anyone know how hi of pitch I need to go?

Ayuh,...... Welcome Aboard,....... It'll work,.....

But, not very well,...... terribly inefficient,.....

'n, ya may not be able to find a prop with enough pitch to tame the rpms,.....

 

[Dmoneyone1]

I have a 20' maxum with a 4.3 v6 (mildly warmed over)and 1.84 drive and I run a 21" 4 blade aluminum prop... and light load I get 4950 and heavy load I get 4600... have you had it in the water with a 1.47/1.62 (some v8's had a 1.62) drive? if so what was the pitch on the prop then? my best guess you are going to have to go up at least 2" in pitch.

I have not had it in the water yet as I have been restoring the boat over the winter and the leg is my last thing left to do, the guy I bought the leg from was mistaken on the gear ratio so before I swap it I thought maybe I can just use it, boat originally had a 1.47 ratio alpha one gen2 leg but that was ripped off when the last owner hit a dead head

 

[Dmoneyone1]

Ayuh,...... Welcome Aboard,....... It'll work,.....

But, not very well,...... terribly inefficient,.....

'n, ya may not be able to find a prop with enough pitch to tame the rpms,.....

Ya that’s what I’ve been reading, my next thought was to see if I can get a bravo prop on cause I see they go real high in pith, just seen a guy selling a 30 pitch but I don’t know if they fit on alpha drives

 

[Rick Stephens]

You haven't had it in the water yet... stick a 25 inch aluminum cheapie on it and test it out. See what your RPMs are at WOT. Then you might just plan on a different upper gear case for it if it seems that will be needed.

 

[Dmoneyone1]

You haven't had it in the water yet... stick a 25 inch aluminum cheapie on it and test it out. See what your RPMs are at WOT. Then you might just plan on a different upper gear case for it if it seems that will be needed.

no i havnt yet, waiting on the weather to turn a little bit warmer. would a bravo prop work on a alpha drive as there are people who sell hi pitched ones like 28-30 pitch if that high of pitch is necessary maybe bravo would work

 

[Bondo]

Ayuh,..... B-1 props, Alpha 1 props, 'n the large gearcase outboard Mercs can all be interchanged,......

 

[Scott06]

I would start with 4” more pitch than what was on there, 23” if you dont know. Would second to start with an aluminum until you rough it in, unless a prop shop will let you try a bunch.
I think you have an advantage here In That a 23 ft is a fairly large boat for a 5.7 to push so the steeper gearing will be more likely to work with this than if it were a smaller lighter boat. I repowered a 21 ft from a 4.3 to 5.0, kept the 1.81 drive went up from a 19 to 21 prop. works great.

 

[Dmoneyone1]

I would start with 4” more pitch than what was on there, 23” if you dont know. Would second to start with an aluminum until you rough it in, unless a prop shop will let you try a bunch.
I think you have an advantage here In That a 23 ft is a fairly large boat for a 5.7 to push so the steeper gearing will be more likely to work with this than if it were a smaller lighter boat. I repowered a 21 ft from a 4.3 to 5.0, kept the 1.81 drive went up from a 19 to 21 prop. works great.

Thanks for that, if I go to a 23 pitch would a four blade be better then a 3 blade, would it bring rpms down?

 

[Rick Stephens]

Thanks for that, if I go to a 23 pitch would a four blade be better then a 3 blade, would it bring rpms down?

A four blade typically drops RPMs around a 100. The choice is based on how you want to run your boat. If you want better slow speed handling and hole shot, then a 4 blade is great. If you want most top end possible, then a stainless three is your target. You are going to be trial and error with this, so it really doesn't matter 3 or 4 blade. Pick whichever is going to make a good backup prop in your locker and slap it on there. Then adjust after you do testing. Just make sure you don't ever rev your new hunk of iron in the testing.

note: I haven't a clue whether a high pitch bravo wheel will work.

 

[Dmoneyone1]

A four blade typically drops RPMs around a 100. The choice is based on how you want to run your boat. If you want better slow speed handling and hole shot, then a 4 blade is great. If you want most top end possible, then a stainless three is your target. You are going to be trial and error with this, so it really doesn't matter 3 or 4 blade. Pick whichever is going to make a good backup prop in your locker and slap it on there. Then adjust after you do testing. Just make sure you don't ever rev your new hunk of iron in the testing.

note: I haven't a clue whether a high pitch bravo wheel will work.

Thanks for all the help and advice I’m gonna work with that and I’ll let you know what I come out with

 

[QBhoy]

For me. It would all depend on what 23ft maxum you have and what 5.7 v8 it has. If it’s a 250hp carb 4800rpm peak and a 23ft cruiser maxum..you might find a prop to match it (not ideal though).
if it’s a 5.7 mpi 300hp and 5000 rpm thing and a 23ft cuddy or open bow...not so sure. Either way. Never too clever to have such a low ratio on a V8.

 

[Dmoneyone1]

For me. It would all depend on what 23ft maxum you have and what 5.7 v8 it has. If it’s a 250hp carb 4800rpm peak and a 23ft cruiser maxum..you might find a prop to match it (not ideal though).
if it’s a 5.7 mpi 300hp and 5000 rpm thing and a 23ft cuddy or open bow...not so sure. Either way. Never too clever to have such a low ratio on a V8.

It’s a 23’ cuddy cabin the 2300SC, engine is the 5.7v8 thunderbolt ignition, carb

 

[QBhoy]

It’s a 23’ cuddy cabin the 2300SC, engine is the 5.7v8 thunderbolt ignition, carb

So I know a friend with this identical boat. He has a 5.7 and alpha one. He runs a 19” stainless prop on his 1.47 he tells me. Sounds over propped a little achieving 4500 rpm he thinks. That being the case...there may be a prop in the mid 20’s” pitch you can run perhaps (23-25” assumed) Not ideal. But not impossible perhaps.
just what he tells me. Don’t take it as a certainty. I haven’t checked the numbers either.

 

[Rick Stephens]

So I know a friend with this identical boat. He has a 5.7 and alpha one. He runs a 19” stainless prop on his 1.47 he tells me. Sounds over propped a little achieving 4500 rpm he thinks. That being the case...there may be a prop in the mid 20’s” pitch you can run perhaps (23-25” assumed) Not ideal. But not impossible perhaps.
just what he tells me. Don’t take it as a certainty. I haven’t checked the numbers either.

I agree here. And without having much reservations about a 23 inch prop being a huge handicap. There is going to be little difference between a 5.7 on a 1:1.84 with a 23 inch prop and a 5.7 on a 1:1.47 with a 19 inch prop, all else being equal. Maybe a little less efficient on top end, but later on you can address that if warranted with a different upper case.

 

[Dmoneyone1]

So in other words it will work? My fear is I will burn out the gears, it does state under the engines specifications that the 1.84 ratio is for high elevations but where I am(Vancouver) it is sea level, so not ideal.

 

[Rick Stephens]

So in other words it will work? My fear is I will burn out the gears, it does state under the engines specifications that the 1.84 ratio is for high elevations but where I am(Vancouver) it is sea level, so not ideal.

Recommended gear ratios make sense, same as rejetting. A little higher ratio gives more RPM for less horsies at higher altitudes.

You will not stress the gears any more than you would with a different ratio and prop. What wipes gears is over 300HP and broaching your prop under power. Well, that and running out of oil.

 

[Dmoneyone1]

Thank you for all the advice and knowledge, much help, thanks

 

[philray20]

Hello all i have a question regarding Ricks comment mentioning that there is going to be little to no difference between a 5.7 on a 1:1.84 with a 23 inch prop and a 5.7 on a 1:1.47 with a 19 inch prop, all else being equal.

It seems there would be an efficiency problem by running the 5.7 on a 1:1.84 Maybe a little less efficient on top end, or terribly inefficient some could say.

Any ideas why would that be? Perhaps due to propeller slip? Why has the gear ratio been reduced in the first place for larger engines instead of pitching prop?

I'm considering retrofitting a 5.7 on a AGen1 leg which was formerly used with a 4.3 (1:1.84) but perhaps its not a good idea