Andy

I have a heavy 1985 Formula 302 #8,200. Just rebuilt 2 454's .030 9.1 to 1 cr, with vortec L29 heads mild pocket port with 2.18 valves on the intake 1.88 exhaust, cams are comp cams 224 230, and 515, 520 lift @.050. I think with 110 cl. Timing @ 35 deg.The intakes are performer oval ports with 750 vacuum Hollys on top of 1in spacers. Stainless Marine exhaust. My speeds are @3,000 41mph, @3,5000 49mph, @4,000 this is where I hit the wall @58mph. Trim does not help, I gain 200rpm but no more speed and the boat feels too loose. The outdrives are King Cobras with 1.5/1 gears(I think) and spinning 4 blade 23pX14.1/8 dia Renegade Offshore props. I have tried 850 carbs and got 150 more rpm 2mph max. If the cams are too small what do you suggest? If the props are too big would down pitch to 22p be enough to get me to my goal of 5,000 rpm? and who could repitch them? Props look almost the same as Hydromotive Q1V's

KAAMA

iTrader: (1)

Andy, I don't really know what is going on with your boat as to why it won't run higher RPMs, but it certainly sounds like you have a very good engine combination with the cams, exhaust system, heads, etc. My cousin's 461cid engines are very close to yours in components, cams, etc and his engines made 461hp at 5100rpm on the dyno, and 510 foot pounds of torque at 3600rpm and stayed pretty flat until 5100rpm. He has a 1988 32' Baja and with 21' 3-bladed props the boat easily ran up to 5100rpm and still had throttle left, but it was the first time out in the boat and he didn't want to push it. He said he knows he could use a larger prop---preferably a 4-bladed prop.

Also, "Dyno's" 454cid engines are very similar to yours engine specs as well and he has a 31' Sonic. He turns up to about 5300rpm or so, but I think he said at 4000rpm he's running at about 48mph in his boat.

Anyway, I hope some of these comparisons will help you a bit.

awesomecat26

if you figure this out let me know i have a 96 454 L29 engine that i installed zz502 cam 224in 234ex @.050 527lift with a world products intake and 850 holley and can't get it to run upstairs to save my ass trying to pull a 26 bravo 1 4 blade on a 26 ' awesome thundercat and it will only pull 4200 rpm and seeing 52-53mph what a large dissapointment

1BIGJIM

iTrader: (1)

Did you install new valve springs?

Andy

I used the indexable cam gear installed straight up, if I reinstalled it 4 deg retard would it bring my power band up higher?

Andy

Just ran both engines from idle to 4000rpm with my buddy looking at the carbs because I couldnt hear the high pitch whistle after backing out of the throttle. Niether of those carb back secondarys are opening. What colour springs should I be running, I have 14.5 in of vac at idle. Is there a port I can put vacuum on to check the opening of the diaphrams?

PatriYacht

You said you used different carbs with only slightly better results so I think you are over propped. My boat with 1.35 gears and 24 pitch props runs 60 at 4000 so we seem to be close. Your props or your gears seem to be out of whack. Try 21 pitch or 19 even and see what happens.

PatriYacht

Theoreticly 5000 rpm would get you about 73 mph and 5500 would put you over 80 with the props you have. You don't have the horsepower to pull those numbers. We used to have good results with Mirage props on those boats with merc outdrives. Where did the King Cobras come from?

Andy

I bought new Comp Cam kits springs and timing set included

Andy

The Cobras where on the boat when purchased. How do I tell the gear ratio?