Post your engine specs and where the timing is set . We need some details to get it sorted out . If you were running those numbers before the rebuild and lost speed and rpm's after something is amiss and I would bet it is cam choice . Also advanced timing on a marine engine is no good , 34* as compared to your 37* as stated in the other thread .

Then your original engine was not stock. If not stock, then it was better than what you have now.

Stock 260/270hp motor in your boat is not 57mph capable.

We need correct information from you so that we can give you correct information back to you.

Okay, re read your first post. This is what I'm gonna' comment on "4600rpm-4700rpm at 57mph using a 14x3/4 x 21 SST stainless prop"

Which means your GPS speed was right (sorry, I have to doubt when diagnosing) and what that means furthermore is that was some performance work done to your old motor.

The person who built your current engine did so to near stock specs (cam and carb wise) and thus you got near stock results.

It's a bummer you thought last tired motor was stock and thus why disapointed now.

Sum of a beatch huh ?

Why on earth running such high octane gas on a stock build?

You also went from 13% slip to 22%. On top of what SB said. If you spin the exact same rpm with the exact same prop and gear ratio there will be no gains anyhow.

I agree. Major slip change.

99.9% Engine builders can only quote what engine is good for rpm wise, not what certain prop on a certain boat will pull it at WOT.

I will have to dig up the specs on this motor tonight and re-check the timing to see what it is at. When I bought the boat, it had the the edelbrock aluminum heads and intake and a stock carb on it. The person I bought the boat from only had it for 1 yr and knew nothing about the motor, so if someone did do some internal work on it, it must have been done 2 owners ago. I am using the same heads and intake as before but a different carb.

Get the blower back!!!!............... Problem solved!!:party-smiley-004:

I originally filled it up with 40 Gallons of Premium from a Wesco right around the corner from the boat launch I use. I took the boat for a ride and it was sluggish and didnt want to come out of the hole at all. The guy who built my motor told me to drain that 40 gallons and to run the super premium from this Citgo, he wanted me to run that because it is Ethanol Free fuel. I told me for every 10 gallons of it to run 1 gallon of the race fuel they offered at the same citgo. He said the race fuel has Zinc or something in it that would be good for the flat tappet lifters in my motor. I drained out the Wesco premium and filled up with the Ethanol Free and man what a difference, the motor ran smoother and came out of the hole alot better. I was 100% skeptical when he told me to switch fuel, I told him he was nuts but I was wrong, it made a difference.

I thought about it, should have never sold it.... I have so much money into this boat, I don't know what to do anymore