Prop pitch

[jfair]

I recently bought a Crestliner 2100 Rampage deckboat . It is a 2000 model aluminum deep v.2002 mercury 125 outboard is what's powering it.My prop is a stainless three blade marked ts1116.... boat has great holeshot and tops out at 40. At cruising speeds it is drinking alot of fuel so im looking to get a higher pitch put on it. Tach just got replaced so im not sure what rpm im turning but I figured I would see if anyone had some thoughts to which pitch I should go with.

[Brian@BNE]

correct pitch for an outboard is the one that allows the motor to reach max. rpm at WOT. If you try for a longer pitch than you have now, but cant reach max rpm then you will start to damage your motor.

'drinking a lot' is pretty vague. If you can supply some figures then somebody will know whether that's in the normal range or not.

If you want improved economy you have two choices: remove any unnecessary weight, or cruise at a slower speed. Those two things have the biggest impact on any given hull/engine combination for a planing boat.

[jfair]

Ok thanks for the input...all my boats have always been I/o so this is my first outboard. I will do some running and provide rpm, time running,and fuel use then repost.

[Stumble]

It would also be good to know what engine is on the outboard. They made a couple of different models of the 2002 125.

Particularly the 2+2 models (where the engine shuts down cylinders at low speed) have been known to be problematic.

[tunnels]

Originally Posted by jfair

Ok thanks for the input...all my boats have always been I/o so this is my first outboard. I will do some running and provide rpm, time running,and fuel use then repost.

I discovered a good site called boattest.com
They do tests on all kinds a boats so have a look for a boat with about the same hp and size and see the test and see the speed and rpms and fuel usage etc etc

[Frosty]

Originally Posted by Brian@BNE

correct pitch for an outboard is the one that allows the motor to reach max. rpm at WOT. If you try for a longer pitch than you have now, but cant reach max rpm then you will start to damage your motor.

Staight out of the owners manual and not strictly true,--- bit over the top dont you think. More rule of thumb--something to aim for.

If its a real light boat and you never use full but cruise, a high pitch can be used,----without damage.

[bailarjw]

Why buy a motor if you won't use full power? Doesn't it make sense to spend less on a smaller motor that you'll run up to full?

[tunnels]

Originally Posted by bailarjw

Why buy a motor if you won't use full power? Doesn't it make sense to spend less on a smaller motor that you'll run up to full?

Why keep flogging a small motor all the time when you can use a bigger motor that will last maybe twice as long because its only using part of it hp !. I had a 75 on my old boat and the motor struggled all the time Now i use a 115 and its shear delight because there is only a few times i know i can use all those horses but i can still go at the speed the old 75 went at and have lots in reserve . Plus the 115 uses less fuel than the wide out 75 dong the same things .

[eyschulman]

You can over prop some motors and get away with it. Don't make it right and the next owner of that motor may find out why. Working staight out of the book may be a little stiff but truth be told not many of us messen with boats know as much as the guys who write the specs and test the motors for the company that makes em.

[tunnels]

Originally Posted by eyschulman

You can over prop some motors and get away with it. Don't make it right and the next owner of that motor may find out why. Working staight out of the book may be a little stiff but truth be told not many of us messen with boats know as much as the guys who write the specs and test the motors for the company that makes em.

I love that term ! you can get away with it !! Covers a wide range of stupid things people do !.
Why over prop??
Why do you want to over load your motor all the time ??
why abuse the poor motor ? just for the hell of it!! .
It hits you in the pocket any way ,so why be a dum mutt
Costs more in fuel and running costs every time you use it because its over loaded and working beyond its capabilities ,
Costs more in repair because it wears out quicker ,and it becomes un reliable and will break down more often
In a dangerous situation of a boat being damaged and half filled with water it could even cost you your life ! so what have you gained at the end !!

[Frosty]

Its not a problem to over prop a motor!!! BUT--you need to be able to understand what you are doing --full throttle can not now be used.

You have no doubt over propped becaue you have the power to do so and wish to cruise,--common thing to do on yachts that power sail.

But full power must not be used.

[bailarjw]

If you get a bigger motor and an overpitched prop, does the motor really last longer? Do you get better fuel economy?

[tunnels]

Originally Posted by bailarjw

If you get a bigger motor and an overpitched prop, does the motor really last longer? Do you get better fuel economy?

Every motor ever made has a ideal speed to run at so when you find that speed thats where it is economical ! A big motor is doing a fraction of it potentual and at 2500 rpms for me is ideal in my situation and a comfortable cruising speed so all is sweet .
With my old motor at way less hp it was working hard to do that same boat speed and the motors rpms were above the ideal and into the drinking fuel region .
MY YAMAHA MOTOR RANGE IS 2500 RPMS TO 3700 ! STAY WITHIN THAT AND ITS GOOD Go above and the fuel rate goes into the red . BECAUSE THE MOTOR IS BIG FOR MY SIZED BOAT I WAS ABLE TO FIT A MUCH BIGGER PITCHED PROP AS WELL SO WAS A GAIN BOTH WAYS . MORE SPEED AT LESS RPMS . You need to watch boattest.com and compare some of the boat tests information they give

[Frosty]

A diesel uses 5 gallons of fuel per hour at 100HP used.

This is the rule of thumb.Doesnt mastter what size the engine is.

[whitepointer23]

Originally Posted by Frosty

Staight out of the owners manual and not strictly true,--- bit over the top dont you think. More rule of thumb--something to aim for.

If its a real light boat and you never use full but cruise, a high pitch can be used,----without damage.

i have seen a 115 merc that grabbed a piston because it ran an extra 2 inchs of pitch, i would never over prop one again.