Marine Forum

propeller size

Anonymous user

25 May 2009 23:17:04

Joined: Unknown | Posts: Unknown

hi i have a 50hp 2 stroke tohatsu on a shallow v hull shetland alaska 500. i want to know if going up a couple of inches on propeller size would make a noticeable differance to the top speed of the boat. at the moment we can get about 25 knots on a flat day. would you reccommend going up a few sizes and if so what size? thanks, Rob.

Re: propeller size

costapo

05 June 2009 18:40:32

Joined: 01 June 2009 19:32:36 | Posts: 5

Hi...if there is space for longer blades its ok. Alternative (better) you can put a 4 blade propeller with same pitch from Tohatsu. If they haven't got, try other companies but make sure that the conical hole is the same!!! You can get another 5 knots. But don't forget the rule...more speed = more load = more fuel.
and use always Synthetic oils (must) for much longer life of your engine. I suggest AMSOIL .. http://www.hi-techlubricantoils.co.uk
they also have a special premixed!!

Re: propeller size

Anonymous user

25 October 2011 07:16:54

Joined: Unknown | Posts: Unknown

I'm going to have to disagree on this one.
4 blades gives better acceleration and hole shot, with better torque, but less top end speed.
I also have a tohatsu 50 2 stroke, but its on a thundercat, originally had a 15p stainless prop got 39knots, now ive got an 18p mercury chopper and getting around 47 knots (still testing).
Max diameter prop for a standard tohatsu 50 is 11.5, if its TLDI then i dont know.

Just remember, more pitch = more top speed, less acceleration,
just find a balance between them.