Shaft length?

A.F.C. 8511

Petty Officer 3rd Class
Joined
Dec 7, 2017
Messages
85
200 merc xr6 with 25 inch shaft on 24ft pontoon.
Most toons use motor with a 20 inch shaft, what will the effects of a 25 inch shaft be?
pro and cons.
thanks
 

HotTommy

Lieutenant Junior Grade
Joined
Mar 15, 2013
Messages
1,025
By having more of the leg in the water you will be increasing the drag the motor has to overcome. In addition it will apply more torque to the transom/engine pod, so they will need to be strong enough to withstand the additional forces. .... I ran a 150 HP 25" motor on my 24' pontoon boat for one season without any problems. When I later switched to a 115 HP 20" motor the performance was nearly identical. So that extra 5" cost me about 35 HP.
 
Last edited:

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
Unless this 24' boat has oversize tubes (25" minimum) the weight of a V6 is likely going to overwhelm the boat's balance, causing it to float dangerously low in back. Even if it has the bigger tubes, you may not like it. Engines of this weight best reserved for tri-toons.

If it were not for that, some transoms might allow a creative person to modify it enough where the effects of the 25" length might be minimized. A lot of "if's" gong on there for sure.

Then there's the possibility you might be able to buy some used parts to convert the 25 to a 20" at an affordable price.
 

A.F.C. 8511

Petty Officer 3rd Class
Joined
Dec 7, 2017
Messages
85
Yeah, I saw a good deal on a remanufactured Merc 200 with a 25 in shaft. But I descided to go with the Brand new Merc 115 command thrust Pro XS.
I think its plenty motor for my app.
 

A.F.C. 8511

Petty Officer 3rd Class
Joined
Dec 7, 2017
Messages
85
Went buy and purchased the Mercury 115 CT Pro XS TODAY..😁😁😁
what prope you guys running on your 115 Merc CT?
 

HotTommy

Lieutenant Junior Grade
Joined
Mar 15, 2013
Messages
1,025
I went with a Solas Science & Engineering Co Alu Propeller V6 - 9513-148-15 (14.8" diameter with 15" pitch). Peak RPM with my usual load was about 5100 RPM so I had a prop shop modify it this winter to raise the RPM. It'll be a few weeks before I know what effect that has. ..... FYI, I also needed a trim tab to reduce the torque steer at high RPM. I needed a tab with a large offset to clear the Solas prop.
 

icwingman

Seaman
Joined
Aug 21, 2017
Messages
61
i have a 22 with 115 ct, get 28- 30 out of it with 4 on board and 1/2 tank of gas would love the 150 but i bought all new boat and cost was a factor. just watch what holes you put in in you could raise it up if needed
 
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