SB

iTrader: (1)

A 750 Edelbrock ? I'm not so sure they did on this motor.

92cobalt243

That's kinda what I was curious about...I think maybe he offed some parts (intake and carb) when he sold the boat. So "unknown" upgraded cam that's a part of 527/570 dyno event then is now part of a 750cfm carb creates what kind of limitation/danger?

Baja Rooster

iTrader: (1)

Just a lament, but when I got into powerboats I asked around and found the most recommended mechanic and he knew nothing about the #30 bypass filter, and missed a ton of other specifics. He was a good parts changer though.

A 500+HP motor should be spinning a 23p prop at minimum so a 19p isn't encouraging. A 750cfm seems small for a warmed up BBC. My internet guess that whatever engine is in there is putting out 375-400hp at most.

92cobalt243

Ok, the plot thickens...the PO also had some really expensive 4-blade stainless prop but wasn't included in the deal. I think he wanted more than $500, maybe $800 for it. Maybe the 19p mirage is the stock one for the OEM 454 mag? Would the boat maybe benefit from a prop change?

I saw a CL ad from 2010 that states the boat ran in the low 70's...I was only able to hit 58 mph in the brief time I have had it. Thanks for the continued help...

phragle

iTrader: (3)

again in English please??

92cobalt243

Sorry, I think the previous owner stripped some bolt on parts, different intake, carb,& 4-blade prop before he dumped the boat. Trying to cut his losses. He left the exhaust and upgraded cam (which I do not have any specs).

phragle

iTrader: (3)

A couple things here...

What ratio is your drive?

If its a standard 1.5 and you were doing 58 with a 19 pitch prop, your tach was probably starting to smoke,,,

with a 1.5 gear in a smaller boat and a 23p prop 58 is around 4400 rpm

So what kind of speedo and how accurate?

given an avg prop slip of 12% or so 58 on a 19 pitch is about 5500 rpm.

So if your spinning 5500 rpm its probably not going any faster because your may be sitting on the limiter... if the engines built for it, if not your boat may not be the only thing floating.

You need to try a 23p because by the math is seems like you have been running the car floored in second gear wondering why it wont go faster.

92cobalt243

The boat's tach has never been over 5k the couple times I've tested it...maybe it's not too accurate ��. I did check my speedo vs gps app on my phone and it was pretty close. Maybe that's the cause of banging. I'll get the VC's off tomorrow and see if anything broke.

phragle

iTrader: (3)

plugging the numbers in, with 12% slip and a 19 p prop doing 4900 rpm would be right if you had a 1.36 ratio bravo..... Why it would have a 1.36 instead of a 1.5?? unless somebody toasted a drive and threw one on....

92cobalt243

No, it's the original Bravo One drive (I have the tag) w/ 1.50 ratio.