lower unit 20 or 25" whats the differance?

stylesabu · Jun 6, 2011

Damaged my lower unit towing boats off the water up in canada last week, nastyu wind storm didi a lot of damage.my lower unit had already hit a rock at low speed. so what is the differance in a 20" and 25" and where is it measured, and do they inter change?

cdn-pk · Jun 6, 2011

Re: lower unit 20 or 25" whats the differance?

It's the transom length, so top of the cavitation plate (should be about level with bottom of boat) to the top of mounting bracket (top of midsection or top of transom). so an extra long shaft (25" will have a longer shift rod and drive shaft). it depends on the lower unit, how much work it would be to swap them out.

Daviet · Jun 6, 2011

Re: lower unit 20 or 25" whats the differance?

Short shaft vs long shaft. Measure the distance from the transom clamp to the cavation plate.
What engine are you working on, could you post the model number?

JB · Jun 6, 2011

Re: lower unit 20 or 25" whats the differance?

Daviet said:
Short shaft vs long shaft. Measure the distance from the transom clamp to the cavation plate.
What engine are you working on, could you post the model number?

NOT. 20" is a long shaft, 25" is and extra-long.

levi_tsk · Jun 6, 2011

Re: lower unit 20 or 25" whats the differance?

short shafts are 15"

and a 2xl is 30" id think the only difference is the driveshaft and shift rod - now how hard are they to swap?? - i dont know....

stylesabu · Jun 7, 2011

Re: lower unit 20 or 25" whats the differance?

model number j150plssc, thanks

Chris1956 · Jun 7, 2011

Re: lower unit 20 or 25" whats the differance?

OK, you have a longshaft (20") motor. If it is the proper length for the boat, then that is the kind of replacement you need. A longer shaft will not perform well.

SEI makes aftermarket replacements for about $600 or so. You will need the upper part of your driveshaft to use their replacement.

emoney · Jun 7, 2011

Re: lower unit 20 or 25" whats the differance?

Definitely got a longer driveshaft but I think they are pretty much the same at the linkage meaning the shift rod should fit right into your motor.

Somebody needs to correct me here because there's a really good chance I'm wrong, but I thought the extra length was all in the midsection. Since you're not replacing the midsection, you should be able to use your driveshaft and shift rod in the "new" lower unit. It'll be a little bit of a pain getting the shift rod lined up, but it's been done before.

levi_tsk · Jun 7, 2011

Re: lower unit 20 or 25" whats the differance?

emoney i was thinking the same thing ....

and yes the length is in the midsection the older motors had an extension kit to go from 15" to 20" but those dont apply here

stylesabu · Jun 7, 2011

Re: lower unit 20 or 25" whats the differance?

so all i have to do is replace mid drive shaft and and shift rod. any ideas on how to get shift rod out?

levi_tsk · Jun 7, 2011

Re: lower unit 20 or 25" whats the differance?

doesnt it just unscrew?? youll have to look in the top secret files for the length but it should be in there

lower unit 20 or 25" whats the differance?

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