prop size to speed??

[moterboat]

have a 1969 woodson trihull (light boat) with a 79 rude 140,4 hrs on motor since rebuild,run a 13x21 ss cupped prop and it would only turn 38mph at 4400 wot. thinking that as light as the boat is it should have handled the prop well I would have thought, took a little while to get up to speed,felt like the timing was too far retarded,but I had that set at a outboard repair shop..
do you think this is too much prop for this boat? the boat was a fixer upper when I bought it and it had no motor,I purchased this motor and here I am..

 

[WillyBWright]

Re: prop size to speed??

That motor should easily twist a 21 on a light boat. Perhaps there's some deformation of the hull, water trapped in the hull for floatation foam waterlogged, motor not running on all four.

 

[Crownie2]

Re: prop size to speed??

And are you really sure it is a light boat? How light is light? I can't say that I've seen too many light trihulls...

Bob

 

[moterboat]

Re: prop size to speed??

what Im calling light is 1300lbs w/motor

 

[moterboat]

Re: prop size to speed??

what Im calling light is 1300lbs w/motor

the floor is in sad shape,without ripping up the floor,is there another way to check to see if its waterlogged? I replaced the floor in 1997,but first one I ever did,used plenty of resin,but did not know about putting web or cloth under the floor before putting down,and since I had the complete floor out,there was no foam ,just the bottom of the boat and the stringers.,the gel coat is shot,so Im looking for another boat to put the engine on,so I don't want to do the floor again.there is a 1" hole bettween the floor and bottom of the boat in the bildge across from the drain hole for the boat. I still want to use this boat untill I can find another.