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Discussion Starter · #1 ·
I just picked up my new boat on Friday and broke it in today. It's a Shoalwater 14.5' cat with 70HP Yamaha. It has a 16 pitch 4 blade prop. It has a great hole shot with a fairly weak top end of 32 mph. The problem is that the tach only reads 2800 rpm at wide open (32mph). Is it possible that the Yamaha tach is not calibrated for this motor? I've never seen one that didn't hit at least 4600 rpm. I can't believe that it's a prop issue. The motor sounds like it's reving higher than the tach says and it otherwise performs normally. Thoughts anyone?

Thanks!
 

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From Hope and Change 2 Dope and Strange
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To have a great hole shot and be able to move that hull that fast for that low of a RPM tells me your tachs off. I had one with a 60 HP and a 90 HP. IMOP your pretty close at top speed with a 70 from what mine did and the hours of research of have done on this hull. But I did have a issue with my hull, so I really don't know if my WOT numbers were correct to what that hull should go MPH.
 

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Discussion Starter · #3 ·
Thanks Shoalcat! I don't know what can be done about the tach but I'm gonna call the dealer tomorrow. The Shoalwater website said these boats ought to have a top end of 40 (maybe with a 90 but I think that's even a stretch). The dealer put so much oil in the gas that the plugs already fouled after only 4 hours. It ran a little funky with that much oil but I think that it will get a lot better after the break in gas is run through. I also learned that my jack plate goes up so high that the water intake will come out of the water. Guess I'll get them to lower the motor a notch on the jack plate. Otherwise I think I'm gonna like this little boat, it turns like it's on rails!
Have a good one and thanks for the advice!
 

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Sounds like your tach is not set up for the motor. Usually a switch on the back of the tach for different number of cylinders.

GED
 

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sea monkey rancher
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setting is not, # cyls, its poles for the alternator

usually 6 , but call a dealer and be sure give him your model year as well
 

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Discussion Starter · #6 ·
Turns out that there are 3 swistches on the back of Yamaha digital tachs that have to be adjusted for the size and type of motor. I called the dealer and they explained the settings. I did it myself rather than take it 3 hours away to the dealer. Thanks for your responses!
 

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Yes the tachs are all now set for 4 stroke from the factory and had to be adjusted for 2 stroke, Dealer should have caught it, when doing the walk thru and test run. and on the PDI when you picked it up. Glad you got it fixed, it should turn up to 5500 boat with a normal load.
 
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