running a 15hp 4 stroke with a 25hp 2 stroke

[fish_n_hunter]

I have bought a Bass Tracker 165 that was slightly damaged and had no motor. I have removed the console and bought a 25hp 2 stroke tiller Mercury to go with it. With the console removed, I have retrofit the boat for a tiller. I am partial to tiller motors and also to trolling with a gas engine. Here is my question: I want to be able to troll down like a 9.9(or 15) 4 stroke does but I also want to be able to get around the lake. What are the problems if I try to run the two motors at the same time, side by side(a 9.9 4 stroke & a 25 2 stroke)? I think I would want to keep my 9.9 prop stock so I can troll slow. What do I do to the 25 hp prop to max my speed with both motors running? Do I change it? I now have the stock 10.5X11 on the 25. The 25 2 stroke will only be running on long hauls.
Any help would be appreciated.
fish_n_hunter

 

[steelespike]

Re: running a 15hp 4 stroke with a 25hp 2 stroke

In my opinion it would be very difficult to get the motors setup correctly and I think the speed improvement would not match the effort or the fuel usage.I would get the trolling motor out of the water and run the 25 by itself.Get it setup carefully.
Carefully propped, set at the right vertical height, well tuned.Raise it to a point just before venting becomes a problem.A 15 will use about 1.5 gph(gallons per hour) at wot (wide open throttle,the 25 about 2.5 gph.That seems like a lot to gain probably a couple of mph..

 

[Silvertip]

Re: running a 15hp 4 stroke with a 25hp 2 stroke

Getting them set up properly is just one issue. Controlling them both at the same time is quite another and potentially dangerous. Running each one individually is not an issue. But either motor should idle all day with no issues so why run both motors at all. Or, why not sell both and get one 25 - 30 HP 4-stroke if that's your pleasure. In an emergency operating two throttles, two tillers, two kill switch lanyards and two gear shifts with one hand will most certainly result in issues.