Reply With QuoteYou can plug into the motors with a computer and check the tach. we did this when we had an rpm problem with one of our motors. The mechanic went out with me to run the boat, and we checked the tach readings with the computer.
I seem to remember some post in the past saying the rev limiter on a 502 was set at 5050 RPM. (Someone care to confirm this?) The speed was from a GPS - Garmin GPS III+. The prop was changed to another 23P and same results. Now both could be off. The tach in the boat said 5100 but I'm sure there is some tolerance on the reading. I am definitely able to bump the limiter.
You can plug into the motors with a computer and check the tach. we did this when we had an rpm problem with one of our motors. The mechanic went out with me to run the boat, and we checked the tach readings with the computer.
Really? Does Mercury sell the cable to do this?
I don't know, I used Dick Simon Marine. We launched the boat and I drove around at different rpm's while he checked the computer readings against the tachs. Any Merc authorized faciltiy could probably help you out.
Havasu Cig:
I don't know, I used Dick Simon Marine. We launched the boat and I drove around at different rpm's while he checked the computer readings against the tachs. Any Merc authorized faciltiy could probably help you out. Thanks! I'll have to look into it. I wonder if the Gaffrig Tachs can be calibrated?
Hey Essex502, I know everybody figures 9-12% slippage as a rule of thumb, but I seem to have similar slippage numbers to yours, also running 23" 3 blade prop. I'm usually right at 7% but light in the tank, runnin wide open light chop I can get 65.5mph (gps) 4800rpms and thats down around 6%. I've always attributed it to my DCB being a very efficient Vee (light,narrow, and Delta pad) I've never checked my tach calibration, but it was the same when I had the lower rev limiter and smaller prop. I'd like to hookup sometime and try your 23"Mirage+ against my old style 23" Mirage that I had labbed by Gibbs.
Chuck
6% is proably too good. That would be like supercat labbed cleaver range. Either the prop, tach or speedo is proably off in your application. 8-10% would be considered a really good goal for most boaters to strive for. Alot of boats are in the 14% range.
XTRM22:
Hey Essex502, I know everybody figures 9-12% slippage as a rule of thumb, but I seem to have similar slippage numbers to yours, also running 23" 3 blade prop. I'm usually right at 7% but light in the tank, runnin wide open light chop I can get 65.5mph (gps) 4800rpms and thats down around 6%. I've always attributed it to my DCB being a very efficient Vee (light,narrow, and Delta pad) I've never checked my tach calibration, but it was the same when I had the lower rev limiter and smaller prop. I'd like to hookup sometime and try your 23"Mirage+ against my old style 23" Mirage that I had labbed by Gibbs.
Chuck If I don't sell the prop before we can hook-up...We are in Havasu every other weekend. Our next trip is scheduled for the weekend of the August 22/23/24. If you're going to be there we can meet.
dorC:
6% is proably too good. That would be like supercat labbed cleaver range. Either the prop, tach or speedo is proably off in your application. 8-10% would be considered a really good goal for most boaters to strive for. Alot of boats are in the 14% range. I agree the numbers look to good to be true. The boat is not particularly light as Essex tends to put a lot of glass in the hull. The GPS has not been verified against another one and who knows on the Gaffrig tach.
I FOUND A WEB SITE THAT MIGHT HELP YOU OUT.GOTO WWW.GO-FAST.COM/BOAT_SPEED_PREDICTIONS.HTM IT CAN GIVE YOU AN IDEA BASED ON YOUR BOATS CURRENT PERFORMANCE. GOOD LUCK!!
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