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Gearing for more speed!!!

R

Ryntipton

Member
I have a 1972 mercury 500 on my 1986 checkmate playmate. Engine runs good and currently has a 13° pitch on prop (i want to double that), im wanting more speed and better fuel economy. Im just barely touching 35mph since i have 12 batteries, two wetsound rev 8 speakers, 2 amps, a mini keg of beer in cooler, heavy 12 sub with custom box, 6 gal of fuel in nose, and heavy, cmc tilt/trim unit all on a 12' boat.

Do any aftermarket suppliers make a lower unit gear kit that would change my gear ratio for more top end while maintaining my stock engine RPM's?
 
Ryntipton said:
I have a 1972 mercury 500 on my 1986 checkmate playmate. Engine runs good and currently has a 13° pitch on prop (i want to double that), im wanting more speed and better fuel economy. Im just barely touching 35mph since i have 12 batteries, two wetsound rev 8 speakers, 2 amps, a mini keg of beer in cooler, heavy 12 sub with custom box, 6 gal of fuel in nose, and heavy, cmc tilt/trim unit all on a 12' boat.

Do any aftermarket suppliers make a lower unit gear kit that would change my gear ratio for more top end while maintaining my stock engine RPM's?
Click to expand...

Did you say 12 batteries? Maybe that's an electric hybrid Merc 500 you got on there. Surprised the boat floats! :rof:

Anything you get into with the gears is going to be expensive. My gut instinct is that changing the gears in your lower unit isn't going to get you what you want, but without knowing your motor's RPM at the 35 MPH top speed it will be difficult for me or anyone else on this forum to offer any better advice than just gut instincts. It would also help to know if that 35 MPH is measured by GPS or just a mechanical speedometer.

BTW - I have an early 1960's white Merc 500 with 1974 powerhead on it on my Glen L TNT (which is an 11 ft boat). I think 35 MPH on your rig is a good top speed and I doubt that the Merc 500 is ever going to be capable of much more than that. I know the only way to reduce the fuel consumption of those old Merc inline 4's is to turn them off!! I also have two late 1960's Merc 650s as well - they're all fuel pigs.
 
Switching to a bigger pitch prop will have the same effect, and cost a lot less; same as putting taller tires on a car or truck.
 
Ryntipton said:
I have a 1972 mercury 500 on my 1986 checkmate playmate. Engine runs good and currently has a 13° pitch on prop (i want to double that), im wanting more speed and better fuel economy. Im just barely touching 35mph since i have 12 batteries, two wetsound rev 8 speakers, 2 amps, a mini keg of beer in cooler, heavy 12 sub with custom box, 6 gal of fuel in nose, and heavy, cmc tilt/trim unit all on a 12' boat.

Do any aftermarket suppliers make a lower unit gear kit that would change my gear ratio for more top end while maintaining my stock engine RPM's?
Click to expand...

Change the boat into a giant keg and party boat. Anyone who drinks from the keg needs to tow your boat around, that way you will get much better mileage.

For more speed the only thing I can think off to get more speed is to find a waterfall! Sorry I could not resist!:poke:
 
Do you have a tach, you really need to know what the engine is doing, maybe possible you have a too large prop and you aren't getting the correct rpms???? I have dropped in pitch to get the motor revved up into the power band. Good luck, keep us posted on progress.
 
A tach is the next item im installing, ill do it before purchasing a prop. I've been lookig at this bad ass gps speedo / tach combo. Its like $300 so it will have to wait till after x-mas
 
Ryntipton said:
A tach is the next item im installing, ill do it before purchasing a prop. I've been lookig at this bad ass gps speedo / tach combo. Its like $300 so it will have to wait till after x-mas
Click to expand...

There is a very accurate GPS APP for iPhones speedometer
 
Chellems said:
There is a very accurate GPS APP for iPhones speedometer
Click to expand...

I currently use an app based gps speedo, but i need a tach and have a open hole in the dash, my thoughts are im going to keep this boat so i might aswell fix it up how i really want to the first time, otherwise i'll just end up changing it later.

Im thinking about this one...
 

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Ryntipton said:
I currently use an app based gps speedo, but i need a tach and have a open hole in the dash, my thoughts are im going to keep this boat so i might aswell fix it up how i really want to the first time, otherwise i'll just end up changing it later.

Im thinking about this one...
Click to expand...

Looks like a nice gauge. I can't argue with you I had a GPS Speedo installed in my mate. Best of luck to you.
 
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