I have a 97 35' Fountain w/565 hp @ 5800 rpm. I am currently running 89.6 on the gps at 5600 rpms. I am installing -2" imco's. My question is what have other people found as far as performance gains? Will I have to re-prop or will I pick up the extra 200 rpm's that I am looking for? As well as what speed increases should I except to see. I was told 5 mph. I question that number though.

Also, I have read some interesting threads on drive toe out. I am assuming that would make the props closer together? I have heard any wear from 1/8"-1/2" out. I have no clue wear mine are at now. Does anyone have any opinions on this or should I just check them and make sure they are at 0?

Any input would be greatly appreacated. Thanks in advance.

Toolbox

I just asked some of the same questions
yesterday.

.....Lets hear some feedback.

i would put stellings boxes on it if u dont have as that will get your props in better water and also let u adjust your x even more,, hmmmm i might know someone selling some,,,.
i would spin biggger wheels if u can if u can get same rpm with bigger if i could.. it will be interesting to see what the experts say,, i was told boxes 2-4 mph and same for the shorties, i am reall curious on the toe issue too..
good luck get the big #...

ttt

do they have cones on them??...what is your X???

Tool,
I would first align the drives straight and use your current props. Based on my experience, a speed increase of +4 to 5 MPH is a good estimate for a 90 MPH twin engine boat. Your RPM may not change much as you improve hull efficiency (less drag) and reduce prop slip. I do not think your boat will respond well to the drives being toe in or out at these speeds.

I am assuming that they will look just like the ones in the brochure. I wasn't asked if I wanted them with or with out nose cones. I assumed there was only one style.

As far as the "x" dimension goes I don't know. The guy I bought the boat from bought it new in 97. The bottom wasn't blue printed or nothing so I am assuming that it would be were all other 97 35' fountain's are at from the factory. Is there any way to call the factory with my vin # to find out?

Thanks for the input. Any more would would greatly appreaciated.

toolbox,

As far as toe in or out this is something you have to work with. My experience with the race boats shows that toe in/out can change handling, acceleration and top speed. This is something you just have to try until you find a set-up that works for you.

You need to calculate your current prop slip and then calculate the prop slip after you install the new lowers. You may or may not need to re-prop. The prop slip gives you a good picture of how efficient the boat is. It's a useful tool to help get the most out of your boat.

It would also be a good idea to try turning the props both in and out with the new lowers as well.

Matt

ttt