1992 70hp lower unit

[Stefanne]

What size of hp and years interchange for lower units. We found a 115 hp lower u it and didn’t know if it would fit in our 70hp. Last year we switched out your lower unit to a jet after we had a accident with a tree, the jet doesn’t get in plane as I don’t think it has enough power now. So we want to w=switch back to a propeller. We need to find a used one. Looking to see which ones would be interchangeable with ours

 

[flyingscott]

89 and up are direct interchange and only 3 cylinder lowers. I believe the 78-88 3 cylinder lowers fit but you have to have a 1989 or newer fine spline driveshaft. But I am not sure on that somebody else may know. 4 cylinder lowers will not fit

 

[Stefanne]

Will a 115 fit on a 70hp?

 

[flyingscott]

Will a 115 fit on a 70hp?

I did say 4 cylinder lowers will not fit. A 115 is a 4 cylinder.

 

[oldboat1]

No expert on jet drives, but there aren't very many moving parts. Did you determine what was damaged? Or maybe you are saying the jet drive you substituted for a conventional lower didn't have enough power to get the boat on plane. That may mean the motor is underpowered for the boat using a jet drive. Is the motor in good running shape with no damage?

 

[flyingscott]

There is a 30% maybe more loss in power going from a prop to a jet.

 

[Stefanne]

We want to get rid of the jet and go back to a regular lower unit with a prop because the jet doesn’t have enough power to get the boat in plane. My question is about the lower unit. Will the 115 hp lower unit fit the 70hp one

 

[racerone]

I guess it was not stated clearly enough.--------The 3 cylinder driveshaft is a smaller diameter / different spline than a V-4 driveshaft.-----So a 115 HP gearcase will not fit / bolt up to a 3 cylinder motor !!