Re: Engine gurus!!!!!!!!!!
 

Z... The slip on my 05 sunsation is right at 14% also w/ a stock 26 Bravo 1.. I was under the impression anywhere between 10 and 12 % was very good. If I had to guess I would say our's is o.k. or a tad high.. :)

Re: Engine gurus!!!!!!!!!!
 

anyone out there if you punch in "prop calculator "on google search it comes up with a ton of free web sites,the first one that pops up is rbbi and you can easily punch in your variables. The only way my baja 272 gets into the 80's is to trim it to maximum trim,i end up with around 20 % slip but it gets the nose light and rpm's good then,some boats like mine weren't built to go the speeds they are going or have big power,iv'e experimented with trim and props and thats what it likes,Smitty

Re: Engine gurus!!!!!!!!!!
 

Don't beat your self up but I think your motors only make about 600HP with those stock GM heads.

It is interesting that you pull to 4300 rpm which is probably where your torque peak is. It will not turn more rpm because you have less TQ at higher rpm. Look at your TQ curve and not the HP curve. If you go down 2" in the prop you will pick up about 400 rpm but probably not run much faster but will have better low and mid range punch. Might even need 4" smaller props.

Re: Engine gurus!!!!!!!!!!
 

Sorry guys
The transmission in my ford went south on me. GPS numbers to come next week.

Re: Engine gurus!!!!!!!!!!
 

500 Bulldogs...540ci, 800CFM carbs, stock GM heads, mild cam...

Re: Engine gurus!!!!!!!!!!
 

that's not far off, 12% on a V is about as good as it gets...

Re: Engine gurus!!!!!!!!!!
 

I finally used a gps last night.
78.2@ 4500 with 27p hydros
80.0@ 5000 with 25p mirage
What drive ratio do I have?
What props do I need?
Im looking for 85mph.

Re: Engine gurus!!!!!!!!!!
 

Whatever drive ratio you have is fine. Generally 1.5:1 is consideredto be a little faster, but my experience there is mixed. I say it isn't a huge factor.

Keep dropping pitch and be sure to compare equiv pitch Mirage with Hydros. Your boat "may" be faster with Hydros, but you got to get them in a pitch that will let you spin over 5000.

Re: Engine gurus!!!!!!!!!!
 

Sounds like you need to ask the drive/prop combo Gurus. They just might skip over a thread titled engine Gurus.

I would be interested to know if the Fountain guys feel that those boats like a 1.5 ratio (slow prop speed) drive with a bigger pitch prop rather than a 1.3 ratio (higher prop speed) drive with a smaller pitch prop.

Even though you end up with the same engine RPM, prop pitches and speeds are different. Some hulls respond better to different combinations.

Re: Engine gurus!!!!!!!!!!
 

I don't know what props you need but your getting closer,like i said on your thread a few wks ago you don't have 1.50's(based on your speed vs rpm's) you probably have 1.36's,i see your speeds are much higher with the lower pitched props,which i also suggested when these guys were going on and on about your motors running right (i could see 1 not running right but not both). It sounds like a 24 pitch merc 4 blade will put you about where your looking,Smitty