what propeller should I use for 1995 Force 40?

[reitsma]

This is the case:

15" glassfiber daycruiser, installed 40 HK '95 modell Force, good condition, well maintained. On full throttle it goes roughly 19-20 knts, original propeller.

It goes in 'plann?e' about ca. 15-16 knts, since it feel likes it's "all or nothing" to get it up to speed I was wondering a stainless steel propeller could get some more fuel efficiency and faster response, any comments on that?

What propeller should I use, there is so much to choose from...

Thanx!

L.

 

[steelespike]

Re: what propeller should I use for 1995 Force 40?

Please read the stickies at the top of the page.
We need prop size, usually on the barrel or under the prop nut.
present max rpm and speed ,in mph would help. No tach? check out the tiny tach.reasonable,easy to install.

 

[hwsiii]

Re: what propeller should I use for 1995 Force 40?

Reit, welcome to Iboats prop forum and we will try to help you as much as we can, but there is certain information that is needed in order to help you. Working over the internet and not being able to see the boat or prop the question is about makes it much harder to propose a solution to the correct prop that you need, and most people don?t know the make and model of the prop . When we get information in bits and pieces we continually have to look back and forth to try and piece the information together. The following form has all of the information that is needed to help you with your problems in finding the right prop. If you do not know all of the information that is asked for on the form please give us the most information you have available as I have a program I designed to find the right prop for any planing hull boat that needs this information. It requires time to find all this information when we have to look for it and in my defense I expect you to be willing to expend as much effort in finding the right prop as I do. We hope to be able to help you get the best prop we can for your particular uses, and this information is required to do that.
It is not as simple to pick the right prop as most people coming to this forum think it is, that is why we ask so many questions, it is for your benefit we ask all these questions. And if you have a stainless steel prop or are changing to one the blade geometry of the prop can make a lot of difference in speed and RPM. Most of my calculations are done assuming an aluminum 3 bladed prop will be used, when changing to a SS prop or changing within SS props we need to discuss what you are trying to accomplish.

Iboats Boat and Motor Info

1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make and model of motor
7. HP and gear ratio of motor IMPORTANT
7A If you have a mercruiser and don?t know the ratio get your serial off the outdrive and go here http://www.sterndrives.com/mercruisersterndrives.html
8. Manufacturer?s recommended WOT range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. If you do not have a tach you can buy a Tiny Tach for $ 50
14. Are you at sea level, or a much higher elevation
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the forgoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
17. Does the prop show any damage that you can see
18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.

H

 

[reitsma]

Re: what propeller should I use for 1995 Force 40?

Thanx, will check things out, so far I can report this:

Engine: Force 40 1995, serial OE123602, original motor/prop good condition, not tampered with.
Top speed 43km/h~ 27 mp/h at ca. 6300 rpm (full throttle),
gear ratio 2.0:1,
reeds: .010 stand open max, .280 in +/- 0.010 in (7.1+/-0.255mm) reed stop max,
trim adjust pin in '2nd hole' (ca. 5 degrees slope)

Boat: Skibsplast 15 VS, see picture of brochure below.

Hope this helps so far.

Edit: mostly used with 2 adults + 3-4 children. Full gas tank, 22 liters + 10l spare, used only for pleasure, f.ex. towing tubes, small tours round the coast. We are at sea level.

 

[reitsma]

Re: what propeller should I use for 1995 Force 40?

@hwsiii:

What does WOT rpm stand for?

Thanx.

 

[hwsiii]

Re: what propeller should I use for 1995 Force 40?

Reit, I have that exact same motor and it was not designed to turn over 5,250 RPM, and you don't mention what prop you are using with it. You certainly are overreving it though.


H

 

[hwsiii]

Re: what propeller should I use for 1995 Force 40?

Wide Open Throttle, sorry.


H

 

[reitsma]

Re: what propeller should I use for 1995 Force 40?

Oops... 6200 was a typo, should be 5300 at WOT off course :redface:

I will try to check my propeller later today.

L.

 

[hwsiii]

Re: what propeller should I use for 1995 Force 40?

LOL, that makes sense. OK I will be glad to help.


H

 

[backyardangler]

Re: what propeller should I use for 1995 Force 40?

I have exactly that motor on a 16' flats skiff. I put a 10" x 14" vortex aluminum on mine. I get about 4600 RPM's, takes a while to plane. Goes about 21mph. The vortex props are cheap without the hub kit, I think $57 here on iboats. I would like to get mine up to 5000 rpms. Hope it helps.

 

[hwsiii]

Re: what propeller should I use for 1995 Force 40?

Backyard, I run a 10 3/8 x 14" Apollo on my 16' Sundance Flats Skiff at about 4850 RPM and 29 MPH on mine. You are showing a 31% prop slip at 21 MPH and something sounds not right with that. I only have a 6% prop slip on mine. Yours must be real heavy and maybe needs to be raised up more on the transom.


H

 

[backyardangler]

Re: what propeller should I use for 1995 Force 40?

Backyard, I run a 10 3/8 x 14" Apollo on my 16' Sundance Flats Skiff at about 4850 RPM and 29 MPH on mine. You are showing a 31% prop slip at 21 MPH and something sounds not right with that. I only have a 6% prop slip on mine. Yours must be real heavy and maybe needs to be raised up more on the transom.


H

Wha, Huh, 30MPH? Dang, I may obsess on this. Do you have a 40HP?

You obviously know WAY more about this than me. Do you think I need to get up to 5000 rpm's? It's a zippy little single hull skiff with an agressive Vee. I wouldn't think it would be draggy. The cav plate is just in line with the bottom of the hull. Man if I could get 5 more mph I'd be thrilled. Tonight I did 4500 rpm's, which I know is low, and got 19.5 kts. 31% slip, well that ain't good.

 

[hwsiii]

Re: what propeller should I use for 1995 Force 40?

I have a 1995 40 HP Force motor stock. Move the motor up two holes higher than it is now, but you will need to change props to 12" pitch like a Black Max aluminum with a higher rake and cup on the trailing edge to run it that high. In the meantime raise it 1 notch to raise your RPM up to see what I am saying is true, but there is a chance that particular prop may ventilate but try it anyway. it will raise your RPM up probably 100 or more RPM.


H