Upper drive ratio difference

[ttexastim]

Hello,

I have what I beleive is a Merc. alpha 1 gen 1 1.84R upper drive (engine is a merc 140hp). The upper unit is stripped out and I am looking for a replacement. I may have found one that is a 1.98R alpha 1 gen 1, and the price is pretty incredible. So ... would it be bad to go from the 1.84 to the 1.98? What would it do? Give me more torque? Anyone know how much it would affect my top speed?

The person selling this upper unit can only make out the letters "8R". After looking at the possible gear ratio's availalbe, I am taking it to be 1.98R. Does that sound right?

I'm new at this stuff so any opinions are appreciated. Thanks.

 

[Lyle29464]

Re: Upper drive ratio difference

If my numbers are right your motor will be turning 8 % faster. This means you could turn 8% more prop. Maybe. I think it will work fine. It is not perfect but close. I would not buy a different prop unless you are turning above the recommended rpm. If you were at the bottom end before you might be right on now.

 

[cr2k]

Re: Upper drive ratio difference

I think you are correct in assuming it is a 1.98R The R stands for Right hand drive. The 1.98 is from a 120. You will probably need to go up in prop pitch or diameter. With the lower gears it might be more beneficial to go up in diameter if you can since you have lower gears you may be able to pull "taller tires" and gain a little more prop efficiency. If you go larger diameter be sure to check clearance on your trim tab.

Also be prepared for a little more torque steer on acceleration if you don't have power assist steering.

You want to prop it to be at Max WOT RPMs (see your manual) with your "normal" loading in the boat.
One pitch up will take 200-300 RPMs of the top.

Don't over rev that 140. They will last a long time if not run to the edge all the time.

 

[ttexastim]

Re: Upper drive ratio difference

Heard back from the guy selling the outdrive. He really looked at the sticker and says that he can make out 1.84R stamped on the sticker. Sounds like a perfect match. Thanks for the help!

Oh ... and Bubba, I did look at my outdrive to verify. I am able to make out ".84R" and the 1 is kinda worn off. I'm very excited at this! Hope to have the boat in the water soon!

 

[oops!]

Re: Upper drive ratio difference

yeah......it will work.....make sure of the year of the uppers and that they are compatible with your transom package.

think of a 10 speed bike......with your current uppers, you are running in 5th gear......with the new ones, you will be running in 4th gear,

that means the engine works less but the shaft/prop speed is lower.

you will loose top end, but gain bottom or have more bottom end prop slip.

you will need to do prop testing all over to determine the best prop for what you use the boat for.

to you....it will SEEM that the motor has more power.

cheers
oops