alpha 1 outdrive has wrong gear ratio

[tfret]

5.7L 260HP V8 engine with what I believe is an Alpha 1 gen 1 outdrive. I can't find a serial number on it anywhere. I just confimed it has a 2.0 gear ratio. One full turn of the engine produces 1/2 turn at the prop. According to mercstuff.com, I should have a 1.5 ratio. I need to know how to confirm what drive I have, and exactly what parts I need to correct the gear ratio for my engine. Thanks.

 

[dubs283]

Re: alpha 1 outdrive has wrong gear ratio

s/n should be on the port side of the upper housing on the decal, if the decal is missing, it may be stamped in the aluminum there, clean off any marine growth/debris to read it

the drive ratio should be in the same area too

if you can't find the s/n or ratio, you will have to count the upper gear teeth and look in the oem manual to verify gear ratio

to change the drive ratio you need a new upper gear set which will require special tools and shimming the new gears to achieve proper gear lash

 

[tfret]

Re: alpha 1 outdrive has wrong gear ratio

Nope, no decal or stamped serial number anywhere. I'm sure it's an alpha 1 gen 1, I just looked at an outdrive manual to confirm that. Any suggestions on how I should proceed are most appreciated.

 

[dubs283]

Re: alpha 1 outdrive has wrong gear ratio

Any suggestions on how I should proceed are most appreciated.

see post #2

counting the teeth is the ONLY way you will be absolutely sure what gear ratio you have

even if the s/n or ratio was stamped in the case, who's to say someone didn't put a different ratio gearset in it??

what manual are you using/looking at??

 

[Bifflefan]

Re: alpha 1 outdrive has wrong gear ratio

Id just run a 23 or 25p prop and call it a day.
You can get those those for real cheap used.

 

[Howard Sterndrive]

Re: alpha 1 outdrive has wrong gear ratio

count the teeth to verify
buy SEI upper of correct ratio and sell your 1.98 to someone with a 4 cyl.

might even end up breaking ($), depending on local knowledge of aftermarket drives. I sold a used drive this summer for same as SEI - some people don't want Chinese.

You could reprop, but you might want the extra impeller speed to cool 260HP
Only 1.5 ratio gets the water pump spinning nice and fast.

 

[tfret]

Re: alpha 1 outdrive has wrong gear ratio

I'm looking at Mercruiser service manual 6. If anyone has changed the top gear set before, can you tell me how difficult it is. Might I be better off buying another drive and selling the one I have? I'm running a 19 pitch prop and I'm still 400 rpm below WOT. I've considered going down to a 4 blade 17, but I feel like the engine isn't running where it should for optimum performance.

 

[Lyle29464]

Re: alpha 1 outdrive has wrong gear ratio

I think you have this mixed up a bit. your going in the wrong direction.

need to recheck things.

 

[dubs283]

Re: alpha 1 outdrive has wrong gear ratio

If anyone has changed the top gear set before, can you tell me how difficult it is

again, see post #2 - special tools and reshimming the new gearset

you can read all about it in your manual

you'd probably be better off just buying a different drive with the proper gear ratio and selling the one you have now

 

[Lyle29464]

Re: alpha 1 outdrive has wrong gear ratio

If you have a helper just mark the dampener on the engine and mark a blade on the prop. put it in gear leave key off and bump starter over. with a jumper

If you turn the engine over 6 times and the prop turns over 4 you are correct with a 1:5 to 1 You can just drop 2 inches in pitch

If the prop turns 3 turns you have a 2 to 1 If you change this drive ratio you will decrease rpm.

 

[adogdrian]

I know this is a really old thread but I'm having the same issue. Have you resolved yours and what did you do?

 

[GA_Boater]

I know this is a really old thread but I'm having the same issue. Have you resolved yours and what did you do?

Then why don't you start a new thread?

Closed.

 

[tfret]

Alpha 1 wrong gear ratio for engine

Follow up to my now closed previous thread. Yes as someone else noted the easiest thing to do is get whatever prop pitch you need to get your WOT where it needs to be. That’s the simple solution.

 

[tfret]

Alpha 1 wrong gear ratio for engine

Follow up to my now closed previous thread. Yes as someone else noted the easiest thing to do is get whatever prop pitch you need to get your WOT where it needs to be. That’s the simple solution.