Griff

How does the builder know that max torque is at 5000rpms???? Obviosly the engine was not dynoed. Even if max torque was at 5000, you should then be spinning the engine at least 5500 rpms.

I can tell you for sure that the engine is not making even close to 550 or 600hp.

fireboatpilot

That's what I'm talking about. Too much guessing. Take it someplace and have it put on a dyno. That will answer all your questions. Theres something missing from this story. I think the builder is guessing and telling you somethink he thinks you want to hear. The proof is in the dyno print out. And Griff is right as are others, you should be spinning at least 5500 at wot.

lucky cat

iTrader: (1)

I had a Baja 260 which is a slower hull (4400 lbs) when i had my 502 in it with around 475 hp with 1.5 bravo i ran 68mph gps with 25 pitch 4-blade prop at 5200rpm...your cam sounds way small i ran about .632 lift hydraulic roller cam with solid roller lifters, plenty of power over 3800rpm...
my buddy is running the same cam in his 540 efi procharged m-3 motor running around 900 hp

If this helps at all...

AIR TIME

my motor made 637tq at 4800 and red line was 6000. I made 600hp at 5050rpm and maxed out at 670 at 6000rpm then it dropped off, I will check my plugs, but my builder had me take out the fitting at the gas tank and use a straight through fitting at a 1/2'' and also upgraded my fuel pump lower. I will look it up. and my be pull the motor out and have someone dyno it thats 600 and up around here. and stay with a 3 blade mirage 25 or 27 for now and if you plan on staying with stock drive height you could try a mod 4 blade rev4 from brett. after you get your motor fixed sounds like 400 to 435hp right now, I will look up my stuff been busy blew the rearend in the jeep and my back is a mess from the shingles I came down with.

Outlaw00024

yes he told me not to rev out over 5200rpm... hydrolic rollers.. im guessing..

Outlaw00024

havent been on here much... I took the stock mufflers off. gained 300 rpms with the 26 4 blade to 4550 rpm.. it is at a great shop now and they will dial it in with proper jetting as it is at 84 in both primary and secondary with a 850 HO holly double... max timing is too low as well at 34 can go up to 36 to 38 ive been told... hopefully this weekend we can find out..
I am pretty sure with out the fine tuning we are at around 68 to 70 mph with the 26 and I now have a 24 4 blade to try out which should put me right at 5200 rpms.. will keep you all posted..

I will try to post results as soon as I find out..

Outlaw00024

he is apparently going by previous builds and experience.. so I am told................

Ghostrider

Your cam lift and duration (lift w/ 1.7 rockers is .612" I and .629" E is in the range of the crane 741 hyd roller cam. Crower has a similar cam with the same duration and LSA that makes peak hp at 5675rpm! (Peak torque is at 4270rpm.)
So if your builder says your peak torque is 5000, A: he's on drugs, or B: he's off the drugs but didn't properly dyno tune your engine. You should be getting WAY more revs out of a 515ci, especially with your bottom end.
If you have a limiter, what's it set at? Try jacking it up and taking it out for a real strap, see how much you can get.

I run a 25P mirage plus with 550 hp but I think my boat is lighter. Your engine with that cam and set up should want to rev way more. Back your timing to 34 to be safe and see how far she'll go. If she won't rev past 5000, it's something else like fuel supply causing your issues.

Good luck mate, keep us posted!