Differences between 20" and 25" Lower units?

[MakoATX]

Hello,
I'd like to know the differences between a 20" and a 25" lower units?
Do they have the same gear case housing and the difference is just longer shaft?
I have a 99 XR6 150 with 20" lower unit. If I want to replace the lower unit with a longer one ie 25" but I don't know if I could simply swap out the 20" shaft with the longer one and get some kind of adapter/trim piece to compensate the 5" different? Or do I have to buy a new 25" lower unit?
TIA.

 

[Jeep Man]

Re: Differences between 20" and 25" Lower units?

Hello,
I'd like to know the differences between a 20" and a 25" lower units?
Do they have the same gear case housing and the difference is just longer shaft?
I have a 99 XR6 150 with 20" lower unit. If I want to replace the lower unit with a longer one ie 25" but I don't know if I could simply swap out the 20" shaft with the longer one and get some kind of adapter/trim piece to compensate the 5" different? Or do I have to buy a new 25" lower unit?
TIA.

Same gears. Kit is available and consists of a longer shaft and a 5" spacer. I spoke with Bass Pro and they do their own conversions when needed after a boat is sold.

 

[achris]

Re: Differences between 20" and 25" Lower units?

Hello,
I'd like to know the differences between a 20" and a 25" lower units?
Do they have the same gear case housing and the difference is just longer shaft?
I have a 99 XR6 150 with 20" lower unit. If I want to replace the lower unit with a longer one ie 25" but I don't know if I could simply swap out the 20" shaft with the longer one and get some kind of adapter/trim piece to compensate the 5" different? Or do I have to buy a new 25" lower unit?
TIA.

I miss the point.. What are you trying to do? You have an engine with a 20" drivehshaft housing. Have you bought a 25" gearhousing and want to swap a 20" shaft into it so it will fit on the 20" driveshaft housing? Of so, the only difference is the shaft... You can swap them over, but you'll need to go through the pinion gear height adjustments....

Chris........

 

[MakoATX]

Re: Differences between 20" and 25" Lower units?

Sorry for the confusing. I want to put a 25" lower unit on my engine which currently has 20" lower unit. Yes, I want to keep the 25" shaft. I've talked to couple of shops, they told me my engine sits a little bit too high on my boat. There're 2 ways to fix this: get a 25" lower unit or get some jack plate. But the jack plate solution doesn't seem to work on my engine setup.
I've seen they have some kit to convert 20" to 25" shaft, I think it's called bay kit extension, but I'm not sure what else I need to buy to make it work for my need. Some says I have to buy the 25" lower unit and a bay kit. I've emailed the place that selling the bay kit & hopefully they will have my answer.

 

[achris]

Re: Differences between 20" and 25" Lower units?

How much too high? If it's only an inch (or thereabouts) then you could fit a hydrofoil on the cav plate...

Chris......

 

[MakoATX]

Re: Differences between 20" and 25" Lower units?

I don't know how much high but 2 of the shops said I could get 25" LU.
I did put hydrofoils and 4 blades props it does help to plane the boat quicker and keep the boat nose down a little.
Do you know any guide line that we would know the correct height for mounting the engine?

 

[achris]

Re: Differences between 20" and 25" Lower units?

 

[sschefer]

Re: Differences between 20" and 25" Lower units?

The bay kit is correct. It is a 5" spacer that fits between your current 20" housing and what will be your new lower unit with a 25" drive shaft vs. the one with the 20" drive shaft that you have now.

There are welders that can cut and weld in the extra 5" onto your current 20" shaft. I've never liked the sound of the idea but they say it's fine. They do almost the same think when they cut them down for race motors.

 

[MakoATX]

Re: Differences between 20" and 25" Lower units?

I've talked with Bay Manufacturing yesterday, they said their kit has a little shaft extension as well. I don't have to do anything with my 20" LU.

The bay kit is correct. It is a 5" spacer that fits between your current 20" housing and what will be your new lower unit with a 25" drive shaft vs. the one with the 20" drive shaft that you have now.

There are welders that can cut and weld in the extra 5" onto your current 20" shaft. I've never liked the sound of the idea but they say it's fine. They do almost the same think when they cut them down for race motors.

 

[MakoATX]

Re: Differences between 20" and 25" Lower units?

Chris,
Thanks for the picture.
I found another one:

Thanks again for all replies.

 

[sschefer]

Re: Differences between 20" and 25" Lower units?

I've talked with Bay Manufacturing yesterday, they said their kit has a little shaft extension as well. I don't have to do anything with my 20" LU.

Yep, that will work, it uses a coupler.