is this speed correct?

[rsimmons42]

I have a 1989 sunbird 16 foot, full fiberglass. I am running a 1977 70 hp Johnson. I clocked my WOT speed (5300 rpm) at 31mph(checked with gps). Does this seem right? Just want to make sure that I am getting everything out of my boat/engine that I can.

 

[ezeke]

Re: is this speed correct?

You will need to know the pitch of your propeller and the gear ratio of your motor to calculate the theoretical maximum speed for your rig. You might then be able to see if you have more slip than normal.

I would expect to prop for a maximum of 5800 RPM.

 

[freddyray21]

Re: is this speed correct?

the rpm range for that motor is 4500 to 5500. 5800 I think is overwinding it, but if you go down a pitch in prop you will increase your rpm about 200, but you will lose speed. It sounds find to me.

 

[rsimmons42]

Re: is this speed correct?

thanks for the responces. The engine model # is 70EL77S. I thought it might be right. I just did some work on the engine recently.. And was the first time to get to WOT.