Cattitude

S.A.M.- Thanks for the input- at least I think some of it was for me.

UT- I suspect the best way to level the boat is with a level on the bottom corner of a sponson (lowest point) running parallel with the boat. Now I know why I couldn't find dyslexic- i was looking under di's

S.A.M. I here what you are saying about the 454's not carrying the same mid range punch as th big inch motors. Mine is a stock 454magefi with stock Whipple setup- ok maybe the pulley's a little on the small side- Dustin claims I should be at 650/740 and i suspect the torque curve is pretty flat allthough i have not seen it. Dustin claims the factory merc cam falls off just past 5400 and that's why he chose not to go farther when recalibrating the rev limiter. Their is definately more to be had buzzing a big inch custom motor. I'm content with the package I have so aside from set-up I'm done. Luckily there are not a lot of fast boats around here to bruise my ego. I have one more test- see how my boat planes pigged out with people- If i can still roll it on plane the 1/2" spacer is staying, otherwise i'll buy a 1". did you ever track down Steve snider- I saw he was advertising in the outdrive section. He's got seat time with a !" on a single step and by now he may have some hours logged with a 2" shorty. Good luck.

Sec Agent Man

U.T. Use a 3-foot bubble level, place in the tunnel on the rear of the boat on the trailer, use the front jack to level front to back. Once you've achieved that, next step go to your drive, place the level on the cavitation plate moving your drive in or out until your have achieved that. Go to your prop shaft center line with a square and measure up. It may take two people to achieve this, but this seems to be the most accurate way to get your answer.

You didn't tell me what cam you had in your engine to determine your RPM. I will try to help anybody who asks, but I can't give you all the answers. I will send you in the right direction.

Hello to Catitude, are you going to Havasu? I am trying to find a clear picture of my boat to post.
The Teacher is giving a lesson.

S.A.M.

RON

Congrats Cattitude!! Mid 90's with a reliable boat ,is SWEET!
You got me ,looking for a used 2" shorty for my 25!!

Good Luck
RON...

Cord

Just a passing thought-when you measure for neutral trim, don't forget that the boat doesn't ride level. While, setting the drive so it's parallel to the bottom might seem to be the "perfect" neutral trim, I actually think that neutral trim maybe a bit higher. You see when the boat rides at speed on the water, it'll take a slightly bow high attitude. If the drive was trimmed so it was parallel to the bottom, then it would be under trimmed. Ideally, when trimmed out you want the prop shaft to be parallel to the water's surface, regardless of the hulls attitude. What I'm trying to say is that the hull is not running parallel to the waters surface. There's a few degrees difference between the two.

So calculate where neutral trim is and keep the setting as a reference. Now go and find what the boat likes. Chances are that it will be a touch more than neutral. Don't get hung up on running neutral trim. Just run what gives you the highest efficency.

Cattitude

Cord, you are exactly right and it's easy to forget that. The most efficiency will come when the prop shaft is parallel to the surface of the water while the boat is underway, which except for in a well ballanced pontoon boat, the hull will always be a few degrees off from the surface of the water -nose up of course.

Would you believe that when i raced small sailing cats you would find fastest speed just an inch away from stuffing the hull- funny looking but fast -relatively speaking of course.

Cord

I once saw a pic of a tri hull pontoon boat running in the 80's. It was suprising how high the bow of that boat was. Hmmmmmm...could that be the poor mans cat? Think about it...

Sec Agent Man

Cord, what I was talking about was how to determine the X-dimension of the drive.

When running a cat at higher speeds the boat does not require a lot of trim, the reason for that is you are packing air under the hull and raising the stern of the boat which will change the attack angle of the drive parallel to the water.

I have experienced different drive angles 1-2 degrees with my mechanical indicator, and the boat will slow 2-3 miles an hour or more. With my application I have found that less trim equates to more top end speed.

Go figure!

S.A.M.

Cattitude

Just wanted to let everyone know I was sticking with the .5" spacer for a net 1.5" shorty. Boat planed fine full of people and 1/2 tank- still hit 90 too. This is on a twin step hull.

Sec Agent Man

Congratulations Catitude! That's a big accomplishment.

tomcat

Congratulations Cattitude - I've been watching this thread with interest. You may remember my spacer adventures of last summer. I must say that the gains you are getting make me sick! I raised the propshafts 2" and only gained 3 mph. When hull drag is high due to weight (1986 Excaliburcat) the gains from reducing drive drag are limited. Good luck in the 90's and post a picture.