Bravo III RPM/PROP....

[brandon08]

I have a crownline 250 cr with a mercruiser 7.4L with a Bravo III 2.43:1 gear ratio. running a 24 pitch prop. RPM are running between 3800 to 4000 to plane??? Seems way high?? Suggestions????

 

[TilliamWe]

Re: Bravo III RPM/PROP....

Yeah, get the proper gear ratio. That ratio is NOT for a gasoline engine. The gas engines use a 1.81, 2.0, or a 2.2 ratio, ONLY.

 

[brandon08]

Re: Bravo III RPM/PROP....

So a 2.43:1 gear ratio is way to high for a gasoline engine? So is that why my RPM is high? What will happen if I continue to run a 2.43:1 gear ratio on this Bravo III 7.4 gas engine?

 

[Bondo]

Re: Bravo III RPM/PROP....

So a 2.43:1 gear ratio is way to high for a gasoline engine? So is that why my RPM is high? What will happen if I continue to run a 2.43:1 gear ratio on this Bravo III 7.4 gas engine?

Ayuh,... It'll over rev, 'n go slower than it should...

 

[HT32BSX115]

Re: Bravo III RPM/PROP....

Yeah, get the proper gear ratio. That ratio is NOT for a gasoline engine. The gas engines use a 1.81, 2.0, or a 2.2 ratio, ONLY.

Yeah it is. It's the drive you would use at Lake Tahoe or other lake located at high altitude......

You should either replace the gearset or sell it and get a "taller" drive.

Mine is a 1.81:1 drive and it came out of a 24' Bilgeliner.......




Where did you buy the boat? Denver?


Regards,


Rick

 

[brandon08]

Re: Bravo III RPM/PROP....

Bought the boat in wis with out a upper and lower unit on it. What would be the fastest, cheap and better way to fix the problem? Replace the gears or take the upper/lower drive off and get a diff one?

 

[Don S]

Re: Bravo III RPM/PROP....

Short of getting a diffrerent outdrive, changing props is going to be your only other option.
3800 to 4000 rpm at wide open throttle (WOT) is not to high, matter of fact, it's to low and your are lugging the engine.
You really don't give much information about your engine (Year, SN, carbed or EFI, etc.) so its hard to give accurate information, but being closer to the 4600 rpm mark at WOT is closer to what you want..

 

[HT32BSX115]

Re: Bravo III RPM/PROP....

RPM are running between 3800 to 4000 to plane??? Seems way high?? Suggestions????

Yeah. That was not at WOT though........He's probably afraid to hammer the throttle....

 

[TilliamWe]

Re: Bravo III RPM/PROP....

Bought the boat in wis with out a upper and lower unit on it. What would be the fastest, cheap and better way to fix the problem? Replace the gears or take the upper/lower drive off and get a diff one?

With that ratio, you might be able to turn 28p props. What is your current WOT RPM?

 

[HT32BSX115]

Re: Bravo III RPM/PROP....

With that ratio, you might be able to turn 28p props. What is your current WOT RPM?

Sometimes 28 and 30p prop-sets are pretty cheap on ebay!

 

[TilliamWe]

Re: Bravo III RPM/PROP....

Sometimes 28 and 30p prop-sets are pretty cheap on ebay!

Yes indeed, because boats with the proper gear ratios usually can't turn them!