1990 35 hp force prop help

[Scooter329]

1990 35 hp force engine on 16' Grumman v-bottom fishing boat. Engine is in great condition and seems to have proper hp. Boat struggles to get on plane with more than 1 person. Boat is fairly heavy with both batteries, gear, gas etc...Once on plane boat will cruise right along, guessing 20-25 mph. Has P273 prop in good condition. Has a steering console with power trim, have tried different trim settings.. Engine sounds like its laboring(loaded to hard, not a lean condition) trying to get on plane. Wondering if less prop would help get on plane easier when loaded. Willing to give up some top speed. Thanks

 

[steelespike]

For the health and performance of your motor it needs to be propped so it makes its max wot rpm. Probably 5000-5500.
Its obvious by your description you need less pitch. There is a 10" pitch here at iboats.
Your speed by a cellphone gps app would help us guess about your actual rpm.
an induction tach would be excellent.
A 10" pitch could likely work fine put one on a get us the gps speed we'll see if it seems reasonable.
When lightly loaded you may have to beware of the rpm.

 

[steelespike]

There are something more than 25 16 ft Grummans. Weights from about 220 to over 700.
Model number or detail description may help.

 

[Frank Acampora]

"You'e gunna need a bigger engine" Face it: with a hull that large you are at minimum power now. A prop change may help some but then again, it may do nothing. Sorry if my answer does not provide any help but "it is what it is"

You might--watch the replies to this one--you might try a hydro foil and see if it helps to get on plane. Oh, boy! we're going to start a real donnybrook over this one suggestion. BUT, a hydro foil only uses four mounting holes, is cheap, and if you don't like the performance it is EASILY removable

 

[steelespike]

While I have to agree more hp would be best; but he is planing and getting 20 to 25 mph estimate
with about a 13" prop. A readily available 10" should give him a good start.While the boat is well loaded it does appear
it does present some surface to help get a load up.
When we went from a 15 ft lone star with a 25 Gale barely able to plane with 4 adults and gear to a bare 18 ft Crestliner
same 25 planed easily with 6 adults and 2 kids.not particularly fast but guessing about 20.
Of course after a couple of years we put a 50 on.

 

[jestor68]

Propco Props(located in Monroe, GA) sells replacement props for your motor, ranging from 9-14 pitch sizes.

The P273 you have shows as a 10-3/8 X 13-1/4 and is listed for light loads/cruising.

It appears that the P287; a 10-3/8 X 11-1/2 should be a better fit; listed for heavy loads. The smallest size is a 9 pitch.

These are exact replacement props just like the one that came on the motor for $ 93.

They have a web site.