1 MAIDEN AMERICA

02 38 Lightning does 102.5 GPS with the 35 and a -1 1.5:1.
Would the smaller prop be a better? How about a 5 blade?

CB-BLR

At what RPM were you running when doing your best speed?

Chris

1 MAIDEN AMERICA

Barely at the limiter. 5350RPM

SkiDoc

iTrader: (4)

That's 14% slip. Might find more there. It's going to be expensive trying new lowers and expensive props. I'd give Brett at BBlades a call and let him tell you what his experience is. With the demo program, it will save you a lot of money...

A.O. Razor

I remember talking to Julie @ throttleup 2-3 years ago, about fountains and slip. She said that the fountain hull liked between 14-16% slip and less slip would slow them down. Maybe Bblades have some info on this.

CB-BLR

I calculate your slip to be between 13%-14% and you are at max rpm...You are very close to max with that combo...you could possibly gain 1-2 mph by going to a 5 blade or gearing to 1.35 and going with a smaller pitched (more efficient) prop...but that seems like a lot of money for 1-2 mph.

In general...less blades equals more speed...but where you might pick up 1-2 mph on the top end going with a 5 blade...you would most probably loose about 2 mph in the midrange cruise speed.

If it were me...I would probably leave it alone...it seems like your boat is pretty well set up.
If you want to go faster...I would probably put innercoolers on your motors...and smaller pulleys...you would probably pick up 3-5 mph...and the motors would run cooler/safer.

We did a Whipple upgrade on a 38 Fountain here locally that had staggered 525's...and it does 113mph.

Give John a call at Eastside Offshore: 206-948-0086

Chris

1 MAIDEN AMERICA

John told me about that boat. Why is mine so slow. 704 HP (and climbing) on Ed's dyno at the limiter. Ed said I'd probably get 730-760 HP if I got rid of the limiter but I don't want to run out of fuel. Stock fuel system and computer have good numbers on the dyno and have not caused any engine problems in 120+ hours.
Do I need to run a 5 blade 34P at 6000RPM to hit 113MPH?
Can the engines do it? I can barely hit the rev limiters as is. Will the extra RPM's/HP do it?
What's that other boat got for gear and prop?
Could the Red Line Heavy Shock 75-250W drive oil in 47F water be stealing a lot of HP?

CB-BLR

IMCO SC drives...Standard length lowers...1.5 gears...34 pitch P5x's.

The props don't work right for the boat...it is hard to get on plane...I think it would do better with some 5 bladed Herings of larger diameter than the 15 inches that the P5x's are.

I have not had a chance to work on prop setup on this boat to date... I believe that I could get it to run faster.

Chris

SkiDoc

iTrader: (4)

Why don't you upgrade your fuel system? In the realm of upgrades it is not that expensive. Look at it as cheap insurance. Imagine holes in pistons. Now think about the cost of repairing this. That's pretty thick drive fluid, I've used Amsoil's marine gear lube with good results and it is thinner than the Merc. by far.
As far as raising the rev. limiter, I won't take mine there because I think the pounding the valve train takes with the hydraulic(I assume you've upgraded to hyd. roller) roller is too much for good long term durability. But I need my equipment to last more than I need the last few MPH. Bob Teaque put it very well when he said that, "you only have so much HP in an engine, either you can use it up quickly by running full throttle or use it up slower with lower rpm's."

CB-BLR

I agree with the drive oil thing...and really like the Amsoil marine gear lube...it seems to really work well in our climate/moisture area.

Chris