Swap 20" shaft to a 25" shaft merc 175 hp lower unit

[Searaydave 59]

I have a 25" shaft merc 175 hp, has a bad shift cam in lower unit. I found a used 20" shaft lower unit, can I easily replace the shafts?

 

[Chris1956]

Re: Swap 20" shaft to a 25" shaft merc 175 hp lower unit

Will the boat perform properly if the gearcase is five inches higher on the transom?

If the motor has a removeable 5" spacer, and you change the studs to the shorter ones, and remove the water tube and shift shaft extensions on the midsection, you can swap the gearcases.

If no removeable spacer, you will need to install the 25" driveshaft, into the 20" gearcase.

 

[Searaydave 59]

Re: Swap 20" shaft to a 25" shaft merc 175 hp lower unit

How do I install the 25" shaft into the 20"shaft gearcase?

 

[Chris1956]

Re: Swap 20" shaft to a 25" shaft merc 175 hp lower unit

That sir, is a complicated issue. You need to disassemble the gearcase, remove the pinyon nut and gear and pull out the 20" driveshaft. Now install the 25" driveshaft, install the pinon gear and nut and then reinstall the propshaft and it's gears, and the bearing carrier.

I recommend you find a 25" gearcase

 

[Searaydave 59]

Re: Swap 20" shaft to a 25" shaft merc 175 hp lower unit

Thanks for the input, I have decided to get my gearcase rebuilt. Thought I had an easy fix.