Allison Grand Sport, Merc 150 gearcase mod

[WavetoWave]

If you want to go to the next step further to maximize efficiency you might want to try to try 2 more things. Turn your seat base sideways and then you can sit a little more to the center and can loose half your counter weight based on your body weight. It also works great with a passenger because you can also slide it more to the side to counter the passengers weight and maybe move one shot bag on your side also based on the passengers weight if needed. The rounded bullet works good for boats in the Allison speed range. Not effective at super high speeds like 135 mph PLUS they start to need a more pointed bullet like what all the super fast Tunnels have in the 160 to 200+ mph range have. I see your case is painted. So if you wet sand cross directionaly starting just behind the bullet down the case about half way back and feather it to 3/4 way back with 600 you will have the right amount of adhesion at the speeds your running for maybe another .5 to 1 mph. The water after rebounding of the blunt bullet will stick to a smooth surface more than one thats lightly sanded. You want the bullet to defect but re-adhere just before the barrel so you have bite at the prop with a denser flow. Alot of drag racers use that trick also its been proven with painted cases in the 1/4 mile. Bet the seat base trick gets you another 1 mph also. You will start to have to be more careful pushing this setup. Its like your running 108 with a 260 your on the edge of the motor and hulls performance. One more bump or a raise up on the motor to try and get the same speed or just a little more than the last time might bite ya and even though your at 80 not 108 she will still turn ya around in a hurry haha What setback you running with that motor 8 or 6? A 200 opti ROS would be a sick motor on there also. So would a 15inch 300xs with carbon cowl and no limiter , ratcheting case and the gas tank moved 2 inches forward.

Those are good tips Whipper. I hadn't thought of the seat base, good idea.

The lower actually looks smooth but isn't. I did it in primer and sanded with 600 or 800 if I remember correctly. The primer holds up better than many paints and I wasn't sure I was finished messing with it.

I have 7.5" of setback. I'm using Darris' first jack plate of the new design, and 2" spacer.

If I changed engines, I'd probably go with the new 150 Proxs and use a TM gen 2 with 1.75.

Always enjoy the input you've given about Grand Sports over the years.

[David]

Reynolds Racing Marine still has a 200XS on their for sale page. Buy the unicorn before its gone

[Ziemer]

The lower actually looks smooth but isn't. I did it in primer and sanded with 600 or 800 if I remember correctly. The primer holds up better than many paints and I wasn't sure I was finished messing with it.

Been using primer for years now on my lowers. Leaves a semi rough surface and is so much easier to touch up than paint. Yet still looks good. ��

[WavetoWave]

Hard to see, but bottom half of gearcase is rough "primer".

[Capt.Insane-o]

Time for a turbo.