speed

can anybody help, i"ve got a redbay fastfisher 166, with 40hp yam . but am getting only 12 mph flat out 9.8 cruising which i think sould be more. outboard seems to be running well , tried different trims to no avail. maybe wrong prop? would be grateful for any advice. it would nice to know what speed I should have. cheers. paintwise.

what weight is in the boat, one adult or 5?
what size is the prop? is it damaged?
Can you do pressure test the cylinders to see what psi they give?
is the cavitation plate level with the bottom of the boat?

with a 40hp you should be somewhere between 20-25 mph i reckon, with one adult and some gear at least.

What kind of a Yam 40? Remote operated? Rev counter to see if it really is in the red zone?
If its a remote set-up with no rev counter to see of whats going on, full travel on the throttle control might not be fully opening the throttle on the engine. Check your cable for sticking, adjustment etc. A friend had a fairly similar problem and a few minutes simple fiddling transformed his boat's performance.

thanks, guys will check prop size ,when I get to the marina, also throttle cable.and no i have not got rev counter, might consider one though. the prop on the yam [remote,electric start] when bought boat is white, I think its a replacment. not the right size I think.because i removed a 30kilo block from bow locker, so normally she should fly. will get compression checked and engine serviced . oh and I only have 2 aboard fishing so not overloaded. thanks again for your help cheers paintwise.

thanks, guys will check prop size ,when I get to the marina, also throttle cable.and no i have not got rev counter, might consider one though. the prop on the yam [remote,electric start] when bought boat is white, I think its a replacment. not the right size I think.because i removed a 30kilo block from bow locker, so normally she should fly. will get compression checked and engine serviced . oh and I only have 2 aboard fishing so not overloaded. thanks again for your help cheers paintwise.

I read on another forum about a guy with the same boat but a 50 hp engine, he was complaining of very poor handling at speeds over 22 mph (knots?). He too had loaded the bow locker with a substantial weight to keep the nose down at speed. Your 40 should certainly give much more than 12 but be aware that solving the lack of speed problem may lead to the handling problem. The boat is rated for up to 55hp engines, the nose up may be due to inability to "trim in" the engine sufficiently to keep the stern up and nose down. The thread on the other forum suggested fitting a wedge to the transom to improve the trim angle.