Quick2500

I believe about 5000 rpm is the top end of mercs wot range on that engine and I think it's rev limiter is 5050. You are probably just sitting on the limiter. Prop it up until you are getting 4700-4800 wot and then run the numbers.

Trash

You don't have enough blade surface area with the Enertia prop for that power and weight combination. I believe, as others have said, you may be at the top of the RPM band for the motor as well.

I would start with one of the following props and see if you can load the motor to pull a max WOT rpm of about 4800 or so. Try a 23" Mirage Plus, Bravo 1 22" or 24" or a Rev 4 in 23" pitch. My guess is the Rev 4 would be your best overall prop. All these props have more blade area and better suited blade geometry for you application.

Quick2500

Exactly! I was thinking Bravo 1 24p, guaranteed to pull that RPM down and use some of the torque that mill can generate.

stimleck

Tried a 22 Enertia and hit 50 mph at 4750. Sounds like I was wasting my time with that style prop

Blueabyss

You tried a 22 what?

AllDodge

iTrader: (1)

You say here you have a 502 mag and the brochure indicates 330hp is mac with a 7.4 (454)

Here you say it is 330hp, agree for a 454
If your hull is not covered in algae or barnacles then paint can actually help. Your boat will not reach a point where surface tension of water has an impact, but a boats hull should never be waxed. A slight ruff surface is better then smooth and waxed.

Agree , OP is hitting the rev limiter

4750 rpm is in the sweet spot. I still think your engine needs checking. When was the last tune up (timing, plugs, cap rotor)?

Quick2500

So here's a few questions. Who installed this engine? Carb or EFI? Were any parts from the 454/330 used in the swap? How many hours on the 502? Are you sure it's a 502 mag?

stimleck

Sorry I should have clarified. Only ran boat twice with 330, no top speed runs. Never dyno'd 502 but it was purchased with zero hours. It was part of the re manufacture program out of Luken Marine in Windsor. It was bought from them and then sold to me still on the shipping crate from when a guy had a project change of plans. As I have learned here there are very few scenarios where you can only be sure of the contents, assembly, or performance of a motor unless its built by one of the few greats. So I would be lying if I said I know all the ponies are available. At some point ill correct my mistake by having it tweaked by AK Racing locally with a proper thru hull exhaust with mufflers. In the interim I would like to improve my slip numbers with the current motor and drive. I have access to a great supply for prop testing Kawartha Prop repair and based on the advice here I will shoot for a lower rpm at peak speed like a bravo or a rev. I thought the rule of thumb was a good 4 blade is equal to a 2 pitch larger 3 blade.

Its odd that I have read so many posts that don't offer the relevant info upfront and I see now that I did the same thing. My bad

tommymonza

Nevermind

AllDodge

iTrader: (1)

Was this a complete turn key 502, carb, distributer, computer everything, or just a long block?

Is it an EFI or CARB

4 blade equal to 2 pitch larger, not that I've ever heard. Only thing a 4 blade will do is give you more lift, but also more drag from the extra blade