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-   -   Can't get rpm's up?? A TUFF! one here. (https://www.offshoreonly.com/forums/general-q/160961-cant-get-rpms-up-tuff-one-here.html)

Wally 06-15-2007 10:21 AM

check float level on the carbs while in the water??? may be right on the dyno but the boat does set different in the water....

blown formula 06-15-2007 10:24 AM

Float levels were reset in the water. No flooding from the jets.

blown formula 06-17-2007 04:31 PM

Seems like everyone lost interest here! BUT, I found the answer finally.
Nothing was wrong with the engines, timing, floats, etc.....
changed props to a 23" from a 26" and WOW!! 80MPH @ 5100rpm!! These will sping to 6000 real easy so I don't know what the top is going to be. Seems my lower unit gear ratio must be different from a 1.50 which is normal.


Any math whiz out there to figure out the lower unit gear ratio??
1.50 upper , unknown lower unit+ 5100rpm@80mph (GPS)- 23" pitch prop???????

badluck 06-17-2007 09:38 PM

Check out this link:
http://www.go-fast.com/Prop_Slip_Calculator.htm

It seems like you have 1.36 gears, but your slip is only 3% at 5100rpm with a 23" prop. Typical slip would be in the 10% range, your tach might be off.

bl

blown formula 06-17-2007 10:20 PM

3 Attachment(s)
That is about what I figured the ratio was.... but the uppers are SUPPOSED to be 1.50's!! Could the lower ratio be different than the "standard" 1.50 for lowers?? That could explain the low slip figure. 3% is next to impossible, but then @ 80 mph I am watching more things than the tach! Maybe I was 100 or 200 rpm off... it is a dual tach with marks every 500 rpm, not 100's. Still, I feel go about the 80mph figure to start with another possible 800 safe rpm to go.
Here is the boat- soon to be called " WILDFIRE".
The last picture is as purchased from "Too Old" aka Trick today.

Rambunctious 06-18-2007 08:04 AM

you could put it in gear, rotate the crank , and confirm your gear ratio by counting or measuring the prop rotation.


maybe rotate 5 or ten revs on the engine to get accurate prop rotation, maybe use starter with coil wire pulled?

then you would know

my drives are 1.36 with speed at 72 at 5000 rpm
true 24 pitch (merc racing labbed props)

Ramb

FASTTIMES 06-18-2007 09:01 AM


Originally Posted by blown formula (Post 2166395)
That is about what I figured the ratio was.... but the uppers are SUPPOSED to be 1.50's!! Could the lower ratio be different than the "standard" 1.50 for lowers?? That could explain the low slip figure. 3% is next to impossible, but then @ 80 mph I am watching more things than the tach! Maybe I was 100 or 200 rpm off... it is a dual tach with marks every 500 rpm, not 100's. Still, I feel go about the 80mph figure to start with another possible 800 safe rpm to go.
Here is the boat- soon to be called " WILDFIRE".
The last picture is as purchased from "Too Old" aka Trick today.

Blown Formula
do you mind sending me your painters contact info, I'm wanting to paint mine this winter-- starting to check around now.
thanks in advance!

blown formula 06-18-2007 09:44 AM

I think your ratio info is so close I do not need to check my ratio. We match almost perfectly......

My painter was in Tulsa, Okla....... "STREET DREAMS". They did pretty good work but don't normally do larger things like a boat, usually custom cars..... It took them 18 months!! I had to stay on their asses all the time to work on it.

The Dash grafics & pinstriping were done by AWESOME ARTWORKS Collin Cauley 918-342-3703 he does airbrush graphics, cad graphics, etc. Good guy & works fast too.
He can probably recommend a good painter too you or he may do it himself, who know?? Painters can be a strange lot.....


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