15 in or 20 in mid

[txdlvryman]

Can anyone tell me the advantage of a 15 in. mid over a 20 in. mid on a mercury 2.5 260hp in drag racing. Can't get a good answer from anyone that is running one.. They just tell u that they were told to run a 15 , but they don't know why.. May sound like a dumb question but would like to hear a good reason to buy one..

[Fish]

I am no expert nor a drag racer, but it might have something to do with less weight and lower center of gravity of the powerhead on the 15". Just a guess.

fish

[scfireman]

I would Guess that everyone runs a shorter mid for a lower center of gravity. I would suppose that aerodynamics would be affected with a 20" leg mounted on the same boat at the same point as a 15". The cowling would be sticking up higher. I'm wouldnt think it would affect the speed or times of a boat dragging a 1/4 mile that much but I could be wrong. :cool:

[BLUEWINGS]

Jeeze! It depends on your transom height! Do you use a set-back plate? (jack plate) I use to have a real light strange looking (transom/bottom) 20'er. I had the motor (225 Merc) all the way up to the 2nd from highest hole. At WFO the nose of the boat would immediately start doing a horizontal figure 8. It was IMPOSSIBLE to drive it out. If you stayed on it, you would barrel roll it. After a bunch of work attempting to rework the pad, a friend of mine bought it from me. Short story, he bondoed the grooves in, said f*** it, raised the motor to the last hole, and drove it. 1 finger driving!!!!!!!!!!!! (had hydraulic steering) Absolutely stable. Turns, straight, every thing perfect. I would still be kicking myself in the ass if I could reach it.

[BLUEWINGS]

[QUOTE=scfireman;1098876]I would Guess that everyone runs a shorter mid for a lower center of gravity. I would suppose that aerodynamics would be affected with a 20" leg mounted on the same boat at the same point as a 15". The cowling would be sticking up higher.

Sorry, absolutely false. Think about it. It's a '20"', or a 15", or a 12" LEG, not power head. The exhaust tuner plate (s) may be a little different, I don't remember. Look at a formula 1 boat. The motor sticks way up there.;)

[Liquid Force]

Try this thread...

http://forums.screamandfly.com/forums/showthread.php?t=38582&highlight=15in+versus+20in

Raceman has some pretty good knowledge on the difference between, the two.

[txdlvryman]

Thanks Liquid Force. That was the answer I was looking for..

[Fl Boy in ILL]

A stock Merc 15 complete mid weighs MORE than a stock 20" mid, I have weighed em, the big diffference is what transom height you have??? Rapid Jack makes a plate to put a 15" motor on a 20" transom. I ran a 20 on my Mirage Polecat (drag boat) for 4 years with a 20" motor, no problems other than it sticks way up in the air, with a 15 you center of gravity is lower thats the real advantage to a 15.

Rick

[txdlvryman]

Have stv with a 20 inch transom, and a cowling for the 20 in mid. so I guess that will be just fine.. Thanks for the info ..

[MODXR6]

My SS weighs in at 395 lbs & most all the 20" promax 225's weigh in at around 420 lbs.

Center of gravity + a stronger mid section