Shaft Length --Jack Plate Question

[Night_Sailor]

Is it ok to mount a 25" motor on a 20" transom using a jackplate?

I found a used motor I like but it is the 25" shaft length.

I would think it is ok, but would appreciate your expert opinions.

Transom seems very sound.

[spareparts]

yes that will work, make sure your transom is up to the job

[Night_Sailor]

yes that will work, make sure your transom is up to the job

Transom seems pretty stout. I am more worried about the fuel tank. It is a bad idea to use an old tank with a newer motor.

I was wondering if a 25" motor would tilt back better.

[Destroyer]

Transom seems pretty stout. I am more worried about the fuel tank. It is a bad idea to use an old tank with a newer motor.

I was wondering if a 25" motor would tilt back better.


Ummmm..... no. A tank is a tank. If it is structurally sound, with no leaks, then the age of the engine it is feeding is irrelevant.

As far as the tilt goes, the pivot point on both a 20 and a 25 is identical, so the degree of tilt will be the same, regardless of the shaft length. The extra length between the two is found in the lower casing just above the impeller section. In fact, it's possible to make a 20 into a 25, and vice-versa with the proper parts.

[Night_Sailor]

Ummmm..... no. A tank is a tank. If it is structurally sound, with no leaks, then the age of the engine it is feeding is irrelevant.

As far as the tilt goes, the pivot point on both a 20 and a 25 is identical, so the degree of tilt will be the same, regardless of the shaft length. The extra length between the two is found in the lower casing just above the impeller section. In fact, it's possible to make a 20 into a 25, and vice-versa with the proper parts.

I'm confused about this. If I mounted a 25" shaft on a jack plate so it sat 5" higher, wouldn't the tilt point be higher?

[Destroyer]

I'm confused about this. If I mounted a 25" shaft on a jack plate so it sat 5" higher, wouldn't the tilt point be higher?

In relation to the transom, yes, the tilt point will be higher, since the whole engine itself will be higher. But the point on the engine where the engine tilts (the pivot point) will be the same regardless of whether the engine has a 20 or a 25 inch leg. The engine pivot point never changes, and is above the lower housings, so they also remain the same. Understand?

[mawshj]

I have a 83 cuddy with a 175 Johnson narrow v 25 inch and it works well it replaced a 175 evinrude 90 degree v 20 inch. the set back and up put the weight a little further back but this is offset because the new motor is a little lighter. this setup work just the same as the 20 inch did. a little faster.