Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

[peanutbay1]

OK guys here are the questions;

Can I switch my mercruiser alpha 1 lower unit (V8) which is the stock gear ratio (I think 1:50) to an SE106 that was purchased for a 4.3 v6 (I believe it is 1:84 ratio).

My boat
1990 bayliner 2755 cierra sundridge
mercruiser 5.7 v8

Can you keep your rpms in the correct range with prop changes??

I have been researching alot about these lower units but I cant find any identification on the unit on my boat currently. I can buy an SE106 at a super price private sale and I hate to pass it up. Can any one help??????

 

[Don S]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

The lower units are the same, the gear ratio changes are in the upper.

 

[Bondo]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

Ayuh,... If you're talkin' about Complete Outdrives,... You'll Never find a prop Big enough to go from 1.50 to 1.84...

If you're talkin' bout Just the Lower Units,.... Don is of course Right, as always....

 

[peanutbay1]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

Yes this would be a complete lower unit change. I am not sure about the ratio of my alpha 1. I assume it is stock. Is the 1:84 ratio (v6) to far from the v8 ratio??? Does anyone know what the ratio should be.

 

[Fishermark]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

Yes this would be a complete lower unit change. I am not sure about the ratio of my alpha 1. I assume it is stock. Is the 1:84 ratio (v6) to far from the v8 ratio??? Does anyone know what the ratio should be.

This is a complete lower unit:

If that is all you are changing, you need not worry about the gear ratio.


If by "complete lower unit" you really mean the complete outdrive, then yes, you need to worry about the gearing.

 

[peanutbay1]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

My apologies!!!! its the entire SE106 out drive that I would be purchasing. I am trying to find out if a lower unit is for a 4.3 v6 could that ratio be used on a 5.7 v8 and make prop changes to keep the boat RPMS correct.

 

[Don S]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

Bondo already answered your question.

If you're talkin' about Complete Outdrives,... You'll Never find a prop Big enough to go from 1.50 to 1.84...

Even if you did find a prop to get your WOT rpm in the proper range, the hole shot would be horrible. That is why there are different gear ratio's in boats.

 

[Bondo]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

I am trying to find out if a lower unit is for a 4.3 v6 could that ratio be used on a 5.7 v8 and make prop changes to keep the boat RPMS correct.

Ayuh,... It's an Outdrive, that's made up of an Upper unit,+ a Lower unit....

I already answered the question,... Even though it ain't the answer you want....

 

[dockwrecker]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

I switched from the 1:50 gears to the 1:84 for my boat and really enjoy the difference. My boat is heavy,(about 4800 lbs wet and ready) sounds like yours is too if it's a 27'. I couldn't pull more than 4100rpm @ 6200' elevation with a 19 pitch prop. Now I'm spinning 4600 rpm with much better launch out of the hole. So I guess the questions are what was your max rpm where you use the boat, what prop are you currently using and would you like it to come up on plane quicker. Worst case you can switch the upper gear ratios. Mine set me back 450.00 installed.

90 Carver Montego 21' (23) "Suspicious Behavior"

 

[Bondo]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

Ayuh,... 6000' is a 'ell of a Difference....

 

[peanutbay1]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

I am in central PA or Jersey shore most times but I dont know our elevation. I dont think its nearly that high. I think our RPMS were 4400@WOT doing about 32MPH with a 17p prop. The boat is huge but the bayliners are not very heavy. It could use some more hole shot though. I am confused......

 

[dockwrecker]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

You definately aren't as high. The lowest elevation I've run mine at is 4000' at Lake Powell. There it pulled 40mph @4600rpm. With the 1:50's it ran 34mph @4100.
I think if I were you and the deal was as good as you say on the SEI unit I'd try it. You can still go up a notch prop wise or at worst change gears. I'd bet you're at least as heavy as mine and probably pushing more air also. I have a hunch it will be just fine.

 

[haulnazz15]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

I am in central PA or Jersey shore most times but I dont know our elevation. I dont think its nearly that high. I think our RPMS were 4400@WOT doing about 32MPH with a 17p prop. The boat is huge but the bayliners are not very heavy. It could use some more hole shot though. I am confused......

Lol, your elevation at Jersey Shore should be pretty easy to figure out.

 

[peanutbay1]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

OK here is my next set of questions:

I have confirmed the SE106 outdrive is 1:84 ratio. I am still unsure of mine but all mercruiser charts show that is should be 1:50 ratio.

Will this require the prop pitch to increase or decrease to compensate?
Will this lower or raise the RPMS without a prop change??

PS
I liked the jersey shore vs the sea level bust!!!!! Duh......I honestly dont know what the elevation is for raystown PA area though.

 

[Bondo]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

Will this require the prop pitch to increase or decrease to compensate?
Will this lower or raise the RPMS without a prop change??

Ayuh,... See my 1st post...

PS
I liked the jersey shore vs the sea level bust!!!!! Duh......I honestly dont know what the elevation is for raystown PA area though

Elevation will Not come into play, at ALL...

 

[fishinpa]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

lol elevation at raystown is around 800ft dont know how much thats going to do for your gear ratio !

but that puts you in the correct elevation ..


fish

 

[Fishermark]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

Will this require the prop pitch to increase or decrease to compensate?

Increase

Will this lower or raise the RPMS without a prop change??

Raise

 

[cooter2506]

Re: Alpha 1 (V8 ratio) switch to SE106 (V6 ratio)

Is there something wrong with your drive. If not just change your prop to 15pitch that will raise your rpms to about 4600-4800 and will give you better hole shot. The whole ratio swapping will drive you nuts.