I'll pull the boat tomorrow and hand turn the engine and count. I hope its a 1.36 but doubt it.

What would the benifit be by going to a 1.36?

Before big pitch props (30+) were available, there was no choice but to change the drive ratio.
There is also a school of thought that the lower ratio gear set is stronger. Bigger teeth and less of them...

Kirk,
Your tach is either way off, or you have a 1.36 ratio.
With 650HP, you should be able to go 85-90mph.
Slap a 25 Mirage plus or 26 Bravo I on that baby...

Keep us updated please,
Happy Boating!!!

Tried a 27P Ballistic today:

73.2 MPH GPS @ 4800 RPM

Turned the motor slow with ignition disabled and tried to watch prop spin, almost a complete revolution, appears to be less than a 1:5 ratio. If this is true, even with a 1:36 gear why can't turn more RPM with the HP/torque I have? Accoring to the prop calculator, I should have a 1:5 which gives me 7% slip.

Wether I have a 1:36 or a 1:50, I should have enough HP to swing a 28P faster, shouldn't I?

Hey Kirk,

Long time! I am sorry to see you are having trouble dialing your boat in. This much I can help with. The drive was never apart and is definitely a 1.5. As you are aware I was running what would appear to be a little less HP and torque, at much higher speeds turning that 29 Mirage + that I had on the boat. I understand you lose a few mph in fresh versus salt but there is obviously other issues. I personally never liked the bravo props on the boat either which may also be costing you a tad in speed too, but I will say what you probably already suspect, there is somethign wrong with your dyno numbers. You should be running much better with that kind of HP. I am sure that Jo would confirm this. Anyway, good luck ironing things out. I miss the boat in a big way.

Regards, Mark

Hi Mark!!

The boat runs and handles awesome, just should have better top end. I remember you told me that you didn't care for the Bravo 1. What prop worked good for you? I tried a 28P hydromotive, too much stern lift.

My latest test was a 27P Rapture:

73.2 MPH @ 4800 RPM

Any ideas on what could be limiting my HP and RPM?

Hope all is well with you. What type of boat are you running now?

Kirk

Years ago in 1983, I had a friend who modified a 330hp engine in his 24' Pantera. The boat was a 1978 and had a TRS drive (1.50 gears) and tranny! With the engine mods he made 486hp @5300rpm on the dyno with dyno headers. Once the engine was in the boat, he went with a GIL dry exhaust system. With the same prop (23' 3-blade Cleaver) we guessed that the boat ran about mid to upper 70's at about 5400rpm. What ever the REAL speed was we don't honestly know---but it was FAST and he took the boat down to Florida and embarassed a lot of people who thought they had some very fast boats back then! It was an all white boat and in 1984/85 he sold it to someone in Kentucky somewhere.

I know every boat is different, but with my friend's 24' Pantera in mind----and I could be wrong, but I believe it seems that your boat should be running much faster and turning more RPM than what you are now.

I agree and am gettin very frustrated. I'm borrowing a scan tool next week to verify timing, RPM and everything else.

The motor is very strong, huge hole shot and pulls the boat easily up to full throttle. Just cna't get the RPMs up. I pulled the flame arrestor to verify full throttle when the sticks are forward, it looks fine.

Any other ideas?

Also measured the bottom of the boat to the center of the prop shaft - 5-3/4"

Try with the flame arrestor off and the engine hatch propped open slightly with a 2x4. What else are you dragging thru the water? speedo pickup, offshore water pickup, trim tabs? How much extra weight do you carry? tools, skiis, etc?