what outdrive to use

[Captain Losten Confuzed]

Dear iboat experts, I was recently given an older 17' Penn Yann (1977?) with a mercruiser i/o engine (straight six) that needs to have some work done on the lower unit. The older gentlemen also included a replacement out drive (upper and low) just needing to be installed. My question is what difference does it make what out drive is put in as long as its an Alphe 1 or older? I see 1.5 and 1.8 ratio out drives and I've also seen out drives marked 120 / 165 / MR. they look the same to me.

 

[thumpar]

They all look the same but the ratio is different to match the engine. You probably want a 1.8? or maybe a 1.6?. I would go with the 1.8?. A 1.5 is going to be hard to compensate for with just a prop.

 

[Captain Losten Confuzed]

I apologize for not having all the information on my boat. I was just seeing lower units in general for sale and couldn't figure out the difference between them. I'm almost positive however that the old lower and the new lower are different (1.5 and 1.8 ratios) If I remember correctly the replacement is the 1.8 ratio but will confirm in about 2 hours

thanks

 

[Alumarine]

I believe the original for that era and the inline 6 was 1.65.

 

[Bondo]

I'm almost positive however that the old lower and the new lower are different

Ayuh,.... The gear ratio is determined by the Upper unit, the lower units can be interchanged,....

A sterndrive, or outdrive, is an Upper unit, 'n a Lower unit,...

For the I-6 motors, a 1.8, or the 1.65 can be used, 'n different props to compensate,....
The 1.65 would be more at home on a small light hull,...
The 1.8 on a huge heavy hull,...