Tach reading at WOT

[ross_larter]

Hope you can help.<br /><br />I have a 1996 Mariner 60hp Bigfoot (2 stroke), with a 13 1/4, 17 pitch prop on it, it has a gear ration of 2.33, so I figure at 5500rpm i should be going about 36mph,(its fitted to a planing hull) when on the water i get to about 37mph and the motor does not sound like it is over reving. <br /><br />The problem is that my new teleflex tach (set on 6p) says at WOT I am at 7000+rpm (I've ran this engine for 15hours before i fitted the tach with no problems). At tick over it sits at about 800 rpm which is normal, and is smooth on the way up and down.<br /><br />Can this motor rev to over 7000rpm?<br />Or does that tach need some sort of resistor for this motor.<br /><br />Please help I do not want the motor to blow it by reving that high.

 

[ross_larter]

Re: Tach reading at WOT

oops, Thats a 13 3/4 X 17 prop, the boat is a 14' deep vhull fibreglass ski type boat, and i has 3 people and all kit/fuel on board at 7000+rpm.

 

[sharkcat]

Re: Tach reading at WOT

I think your tach is out if you were doing 7000rpm the boat would be doing around 45mph allowing for some slip.