Leathl_WS6

My boat used to run low 70's with stock 502MPI's 415hp a side. I upgraded the 502' with some mild head work. A nice cam Holley 850 carbs 9.2:1 CR. Still using the old Merc Log style manifolds the boat still only went low 70's.

After numerous suggestion to change to a better exhaust last year. I finally upgraded to a GIL offshore pipe and manifold this spring. After rejetting the carbs the boat still only runs low 70's.

I just don’t understand it. The motors should put out about 525hp. That’s 200 more hp and still the same MPH.

When checking BAM's speed calc for my boat weight, hul design and power it claims 1000 hp in my boat should run 80+ MPH. I know I have heard of 30 Sutphens with similar power going in the 80's

I am running a set of 25 Mirage props and can only spin them to 5100. I have tried 2 different sets of the same props with the same results. I put a set of 22 bravos for a test and could easily spin them over 5400 but the speed was not there. So I know the motors are capable of going over 5k.

I have been looking for a set of 23's to try but have had no luck coming across a set. Plus I feel I should be able to easily spin the 25's to at least 5500.

The boat seems to run very bow heavy.

Any help would be greatly appreciated

Rob

z.zuperboat

Swap the drives to spin out instead of in. That should give you more bow lift. What kind of drives Bravo or TRS. The TRS will suck up some power.

Leathl_WS6

They are TRS. but I do remember seeing a few TRS 30 Sutphen's with similar setups running in the high 70's. I also remember Bill (Sutphen30) running mid 80's with 550 or so hp a side and TRS he kept blowing them up and went to Konrads.

I will try switching the drives out. has anyone else tried this?

Thanks Rob

BODYSHOT1

give Rich Jr a call...201-274-5445

Leathl_WS6

Thanks Bodyshot i will try him tomorrow.

Rob

lucky strike

iTrader: (1)

Ck your bottom for a hook.

Sean H

dyno the engines.....

AIR TIME

hey you said you still have the log manifolds , thats whats wrong I think! your chokeing the motors. S/M OR C/M SATIN FINISH HEADERS WOULD CLEAR IT OUT. TRICK MARINE WOULD BE YOUR BEST BET OR SCOTT WHICH I WILL LOOK UP FOR YOU IN A SECOND.

AIR TIME

I'm back its SPEED AND CUSTOM MARINE SCOTT AND CATHY AT 850 875 0381 JUST GOT 380SS K PLANES REAL QUICK AND PRICE WAS CHEAPER BY 300 BUCKS FROM MY FRIEND AND GPS SET UP FREDS # 866 921 4553 so if you have twins you should be able to get prices for 2 sets for under $4,000 I have a pair of S/M DRY HEADERS SINCE 1994 JUST FLUSH THEM OUT AFTER USE IBOAT IN THE OCEAN ONLY. I HAVE A 510 650HP.

AIR TIME

SH!t I MISSED THE PART ABOUT THE GILS BUT THE OTHER 2 ARE BETTER HEADERS BOW HEAVY SOUNDS LIKE HIGH X TRY B1 24 OR 26'S see if the bow comes up.