what prop for 60hp rude on a 13ft dory ?

phillnjack · 07-06-2012

I have a 1995 evinrude 3cyl on a 13ft orkney dory.
for those in the states its the same sort of boat as a classic 13ft boston whaler.
Hull shape underneath almost identical.

The boat weight is around 500 pounds, me and a buddy weigh 170lbs and 250lbs.
the engine has power trim so about 250 pounds..so total around 1200 pounds.

At the moment it has a 13 1/2 x 15 inch omc alloy prop and gives max 35mph with fantastic instant acceleration.

im looking for a bit more top speed,

what prop size would you think to get more speed ?

phill

phillnjack · 07-06-2012

would an early omc 13 x 19 stainless prop be good ? or is this too much ?

It does fit on the drive shaft perfect.

I ask as i do have a very good condition OMC prop that was teflon coated from new.
the part no i can see on the prop is 38414 with possibly a 2 at the end.
Definitely says 13x19 on it though.

It is getting on a bit now in age, but its an almost unused prop.!!!

It was given to me about 15 years ago by an ex uk powerboat racer called Nobby Nievens.
It was only used the once on a boat called FLY GUY in the paris to london race back in the early 1970's.
The the boat got put away and sadly never used again.
The prop sat in its box up in the bow of the boat untill he gave it to me.
Ive got the box as well and its looking a bit tattered now, but the prop has no dings at all.
The teflon was starting to just come off a bit and a few rust marks as well, so i decided to get it looking like a polished prop.

Im wondering if this would be a good prop for my 60hp 56ci, or is it just a race type prop ?
It seems very very heavy compared to the alloy prop on the engine at moment.

Any thoughts on this prop ?

pic below

.

**ultrafast30** · 07-13-2012

I have the same setup. The 13x19 works good. My fastest prop is a 11x21 yamaha 4 blade. The boat wants to porpoise as you jack the motor.

phillnjack · 07-13-2012

Hi ultrafast 30

is yours the 3 cylinder or the 2 cylinder engine ?
and what make of boat.

what sort of speed do you get with the 19inch and also the 21 pitch props.

I dont have any porposing problems at all just a lot of torque screw at moment that will be nullified when the prop guard is fitted..

Im running with the engine 1 inch up from level with cav plate.
The boat gets up on plane very very quick, and rides high.
Hitting 34mph with 2 people using the 13 diameter x 15inch pitch alloy.

What yamaha engine is your prop from ?
as 11 inch diameter seems a bit small for this gearcase, i dont have any rpm problems at all, if anything a bit too much rev thats why im stepping upto the 13x19 stainless.

**ultrafast30** · 07-13-2012

I run the propshaft 2" below the bottom of the boat. The 19 runs 41. The little yammi runs 46 at 6000 rpm.

phillnjack · 07-15-2012

so if your running the engine with propshaft 2 inch below boat your trying to use
the 13x19 SST prop as a Surface piercing prop .

I wouldnt of thought these props would be much good for surface piercing !!!!!!!!!!!!!!!!!!!!
I thought it would need to be a proper surface prop to work any good at all ???

When i run mine with the 15inch prop the cav plate is running just barely touching the water at 34/35 mph with engine
screaming its nuts off with me and a friend onboard.
(need to get rev counter working,but i think its way to high rpms)

If i came up 5 inches no way would i get any water in the impellor housing.
centreline of propshaft to cavitation plate is only 7 inches on my engine,
so for propshaft to be only 2 inch below boat you would have to be jacked up 5 inches !!!!!!!!

if your jacked up 5 inches might as well get a short shaft engine and save some weight as well.

I will be trying the boat out again very soon and will be giving the 13x19 a try out.
.
The 13x19 is stainless and 4 inches more pitch than the alloy prop,
if was doing direct swap for 15 to a stainless prop to get same speed i would need to drop
an inch in pitch to14inch !!
so in comparison this will be like adding 5 inches of pitch due to stainless v alloy prop (in theory)

its all just gonna be a case of wait and see test test and test again i suppose

If i was to go to 21 inch i would keep the same diameter for thrust and just put a couple of
vent holes in the prop for acceleration.
I done this with props on a 1992 mercury 60hp, the prop i realy wanted to use was just too slow out of the hole,
but once i drilled the prop it was a different story .

40mph plus would be good for me with the 4 metre orkney, 45mph will be magic. .

.

if the 19 inch pitch SST is a bit sluggish out the hole, ill drill vent holes and see what happens.
can always plug it if dont work . .

phill.......

**ultrafast30** · 07-15-2012

Yes the motor runs high and has no problem with water, 22-25 psi water pressure. It only breaks loose on tight turns when pulling a water skier. And then only slightly. my daughter weighs 115 and I pull her on slalom- deep water start. I do have the motor set back 4" on a jack plate.

phillnjack · 07-15-2012

ahh your using a set back of 4 inches !!!!!!!
that explains a lot.
as soon as you go back 4 inch you would need a 5 inch lift.

so your prop is running about the same height as mine in the water, im 1 inch up from the bottom.

set back is in deeper water when the boat is planning.

i had thought about using a set back, ive never had any dealing with them, read a lot about them but never used one myself.

Have you tried the boat and engine without this ? if so what is the difference ?

is your boat an orkney dory as well ? or other ?

how and where do you fit a water pressure pipe to the engine ?

sorry for all the questions ,

phill