Alpha one ratio change question

[JJJ]

I have a 20' Cobalt with a 4.3 LX merc in it. I just lost - at the very least some bearings in the lower unit. Not sure why as there was never any sign of water intrusion.

I currently have a 1.81 ratio and run a bigger diameter 19P three blade or 19P or 20P 4 blade aluminum prop. Rpms max out right around the 4800 rpm mark.
I very seldom run over 4000 rpms though and almost always cruise in the 2900-3100 rpm range.

QUESTION is, I have been looking for a used outdrive and have found a nice 1.98 ratio at a reasonable price, would it work and work well with just going to a steeper pitch prop?

Or do I just bite the bullet and get a Sei unit or wait to find a 1.81 ratio unit?

Can going to the 1.98 ratio and say a 23P prop give me the same or better performance?
Pros and cons of changing the ratio???

thanks

 

[90stingray]

Re: Alpha one ratio change question

I have a 20' Cobalt with a 4.3 LX merc in it. I just lost - at the very least some bearings in the lower unit. Not sure why as there was never any sign of water intrusion.

Usually the lack of oil is what causes all the problems.

I currently have a 1.81 ratio and run a bigger diameter 19P three blade or 19P or 20P 4 blade aluminum prop. Rpms max out right around the 4800 rpm mark.
I very seldom run over 4000 rpms though and almost always cruise in the 2900-3100 rpm range.

QUESTION is, I have been looking for a used outdrive and have found a nice 1.98 ratio at a reasonable price, would it work and work well with just going to a steeper pitch prop?

Or do I just bite the bullet and get a Sei unit or wait to find a 1.81 ratio unit?

Can going to the 1.98 ratio and say a 23P prop give me the same or better performance?
Pros and cons of changing the ratio???

thanks

Sounds like your drive and prop are dialed in perfectly to the boat. Buying an incorrect ratio drive and then covering it up by buying a different prop just doesnt make a lot of sense to me. Trying to save money with the drive, i get. But it is used, with no warranty! Plus you are having to spend more on a different prop. If it were me... i would pop for the SEI. Cant beat the warranty!

 

[JJJ]

Re: Alpha one ratio change question

I had just changed the oil, but used Amsoil instead of Merc. So either it isn't all it is cracked up to be OR just a coincidence. The oil I drained out looked like new and I've been getting a couple of small metal flakes on the drain plug for a few years now - not really much though, just a few small slivers. Since the boat is only used 1-2 weeks a year and the oil is changed yearly, it is possible that the bearing has been slowly going for some time.

I found a 1.84 ratio drive, newer year with the larger bearings, so I think I will go that route.

Your opinion is what I was thinking also, the other drive though looks nice and comes with gimbal housing, rams, shift cables, etc.

 

[90stingray]

Re: Alpha one ratio change question

I would just stick with the Quicksilver high performance stuff. Its prolly cheaper than the amsoil You could, or have someone, tear down your current drive and see whats going on... It might be something like the bearings have corrosion and are flaking apart slowly. But it hasn't had a catastrophic failure, so i wouldn't give up on it yet. Also, if you are buying a new to you, used drive... it could have the same problems. With used, you just never know. Maybe you could just keep changing oil each year and keep running this drive until it completely craps out... you might get 10 years out if her

 

[JJJ]

Re: Alpha one ratio change question

That's the problem, it crapped out I had to drive 3-4 miles in reverse through the mangroves, a canal and a couple of bays to get back to the launch - other than the mosquitoes and other boaters it wasn't too bad LOL Still better than a day at work!

I'm sure I could rebuild the lower end, not so sure it is cost effective though.

I know what you mean as far as it being a gamble buying a used drive.

If it wasn't for all of the special tools needed, a rebuild would be more reasonable - even then it is still fairly expensive.

What sucks is I bought a case of the amsoil marine lube, oh well on the plus side it will work in the truck.