2000 Force 120 OB - Propeller Recommendations

[Onegazza]

Hi All,

Took a hit to the current Ali prop on my OB today.

I have always said I will replace it with a stainless, when the ali has had it.

So, recommendations on prop size and pitch?

2000 (I know they stopped manufacturing in, 1999 but, mine is stamped 2000) Force 120hp outboard

The boat is a Bayliner Capri 1800 CC

Normal use is a full tank of fuel and 2-3 passengers including driver. Is also used for tubing and water-skiing occasionally.


I don't know the size and pitch of the current prop - the invoice just says 'propeller'. If I had any criticisms with the current prop, I would say my instant acceleration is a bit harsh and top speed could be more (currently 36mph assuming no tide) (ideally what I'm looking for out of a prop). The current props allows it to reach 5250rpm easily.

As I understand, on the later Force models, it's a Mercury gear casing and of course, thru exhaust system.

Recommendations on prop size and pitch?

 

[harringtondav]

Start here: https://www.iboats.com/shop/boat-propellers.html Or check out other prop brand's site. Each has a prop selector tool that will get you close. If you have a prop shop close they can tell you what you now have. If you want to exchange acceleration for top speed you may want to buy a new prop with 1" higher pitch.

Each to their own. I've taken bad hits with my SS props, and had a bent prop shaft to go along with it. Where I boat dead head (submerged logs) are common. I use aluminum. props. They act like a fuse in protecting my out drive.

 

[jerryjerry05]

Your old prop has to have some #s on it???
To change to SS you'll need to go down in pitch say from a 19 to a 17.
Going up 1 pitch would work but!!
It would drop the rpm by 300-400 (maybe more).
You might get a little faster but the economy would suffer.

I changed from a pair of 17p to a 19p
I got 3mph more but the fuel usage went up about 20%

If you can't get the #s off the old prop then contact Bayliner and send them the hull ID #
They can tell you what was on it.

Changing from alum. to SS isn't always a good idea.
If you know for certain you won't ever hit the bottom or run aground then change.
The SS isn't as forgiving as alum.
The chances of breaking the prop shaft after a change is real good.

 

[Onegazza]

Hi All, turned the boat around and had a good look at the prop from the pontoon.

Measuring the prop, it is a 13".

So, there is no manufacturer on the prop BUT:

Part number is TPD 1395. Anyone recognise the manufacturer?

The serial number is 48 77346 A40L 19P


So....

This gives it away I imagine? So, my current prop is a 13" prop with a 19" pitch.

On that basis, if I were to replace with an Ali or a SS and given what I want to get from the boat (Max rrpm and top speed), which sizes should I opt for for Ali or SS?

 

[harringtondav]

Rule of thumb holds fairly true. 1" in pitch change = 200 rpm change WOT. Increase or decrease. Maintaining/increasing your WOT speed is a function of available HP. 120 hp on a 20' boat may be close to being maxed out. You could loose ground with speed and fuel economy as stated above.

Also as I stated earlier and repeated, SS props are tough. Tough enough to damage your prop shaft if you take a bad hit. Alum props tend to give up the ghost before damaging the shaft.

 

[Onegazza]

Ok so, given the current prop reaches WOT 5250rpm then, I should just stick with the same size?

 

[roscoe]

Your rpm's are spot on for that motor.
Prop is a Mercury prop.
Still made and available for $150-$180.

Just google the part number you posted earlier.

If you switch prop models, or manufacturers, the performance may be different and rpm's too.

 

[jerryjerry05]

A stainless prop for your app.
It needs to be 2 pitches smaller
A 19p alum. go to a 17p SS.
Your local Mercury dealer can get you what you need.

 

[Onegazza]

So, the local dealer was going to provide a Michigan prop. I wasn't keen because, they'd already said the blades were quite thin.

I took your advice and didn't go for a stainless prop.

So, I thought I'd try the Turning Point Aluminium prop after a recommendation and seeing a comparison video on YouTube, where they tested like for like against the same boat.

The Turning Point is a 13.25" prop 19" pitch. The result is around 1mph extra, for 150 less revs at WOT, which seems good, given I've gone for similar specs to the previous prop.