should this boat go faster?

[jeffntanya]

1981 Johnson 70
on a 16' fiberglass boat with open bow

4 people full throttle on the gps was showing 43kms whis is only 26 mph

also taking off takes about 15 seconds to get to full rpm. I haven't hooked up a tach yet to see the rpms at full throttle.

also the bottom of the boat has a brown coating that needs to be cleaned off. would this make a big difference?

 

[WillyBWright]

Re: should this boat go faster?

If the coating is just staining, nope. If it's rough, absolutely. Ballpark, that motor should have a 17p prop on it.

 

[jeffntanya]

Re: more info

Re: more info

boat turns 4900 rpms at full throttle @ 43kms/h

with a 17p prop

 

[Chinewalker]

Re: more info

Re: more info

Dropping a prop size (to a 15) might help as your RPM could come up a bit. Aim for 5500 RPM.

Also possible your boat is lugging a bit of water. Have you ever checked to see if the foam flotation is waterlogged? Not uncommon for 25+ year old fiberglass boats...

- Scott

 

[jeffntanya]

Re: should this boat go faster?

what's the procedure for checking the foam? is the foam between the floor?

 

[tashasdaddy]

Re: should this boat go faster?

i like to use a 2 inch hole saw in a drill, cut a hole thru the floor, save the plug. then take some 1 inch PVC pipe, notch one end so it has teeth, then twist it down into the foam. then push the core out. it will be obvious if it is wet. if dry, use some 3M 4200 or 5200 to reinsert the plug.

 

[jeffntanya]

Re: should this boat go faster?

what if it's wet?

 

[jeffntanya]

Re: should this boat go faster?

ok update..

we changed from a 17 pitch to a 15 pitch prop

went from 4900 rpms to 54/5500 rpm

and from a max speed on the gps of 42km/h to 50km/h

is this more normal?

also pickup is much faster