Is current prop ok for my application?

[newkidontheblock]

I just picked up a fairly decent boat for $1100. It's a 16' 1986? Four Winns Freedom I. It has a 140HP Mercruiser inboard engine which seems to run quite well. The outdrive was replaced 3 years ago with an SE106 whatever that is. The interior is immaculate. Anyways, the prop on it is a 14.5x19. I have no idea what the numbers mean but its an aluminium prop and also has this on it "Mi Wheel B". I plan to use this boat for pulling water skis and maybe a tube or two. I also would like to just putt around on the lake at decent speeds (36-43Mph? 50 would be haulin *** and scary as hell so not that fast). I also plan to carry 4-6 adults at times as well. So I think my application would probably be somewhere between top speed and hauling power? I dont even know if thats the right way to look at it lol. So my question is, does this thing have the right prop on it for what I'd like to do? It does have a nice sized chunk missing on one of the props, the other 2 are pretty much fine and very smooth. Currently I get 4600RPM when its wide open and the speedo reads about 37MPH with 2 170lb adults in the boat with the tilt all the way up. If I move the tilt all the way down the nose digs the water and speed slows to about 30MPH which is to be expected since it's pushing itself into the water. The boat seems excessively wide and very deep compared to other 16' boats I've seen which I liked but its probably also heavier because of this. I like the width as its quite roomy for a small craft. It has a sticker on the inside of the boat that says it can handle 1000lbs for a load (7 adults) but the manual on the fourwins site states 1200lbs (yet still says 7 adults, go figure). I assume the sticker is for safety and the 1200lbs is for marketing so it can probably hold 1100.

1) Performance issue you are trying to correct.
None, just a chipped prop atm that looks like it needs replacing. Wouldnt mind a little more speed if possible (39-43mph with 2 people)

2) Current prop manufacturer, model, aluminum or stainless and as a minimum.
Vortex? Mi Wheel B 14.5x19 Aluminum in bad shape on 1 blade

3) Current prop diameter and pitch (required).
No idea. I assume 14.5 dia and 19 pitch?

4) Wide open throttle RPM and speed with an average load (very helpful)
4300 or so with 2 170lb adults

5) Engine/drive make, model, year, and HP
Mercruiser 140HP, displacement 181 CID (dont even know what that means)
Sternengine SE106 outdrive, no idea on the year but it was put on brand new 3 years ago

6) Boat make model, year, length and weight
Four Winns Freedom I 1986/5? 16' weights a ton lol very wide.

 

[steelespike]

Re: Is current prop ok for my application?

86 Freedom 16',7'2" wide chart says 130 hp.181 (C)ubic (I)nch (D)isplacement.1900lbs.
Not knowing the gear ratio but based on the info
I would estimate speeds close to 40 and rpm close to 4,600.
In your text you state 4,600 and 37.In the specs 4,300 but no speed.
I would check that the motor is well tuned,Throttle opening all the way.
Maybe do a compression check.Get the prop repaired and do another test.
If still only 4300 I would suggest a prop change.

 

[newkidontheblock]

Re: Is current prop ok for my application?

It's definately a Mercruiser 140. I had to open the engine cover to see what was in it and it has 140 stamped right on it. I got the CID thing from a small sticker on the engine itself. So I dont know, maybe the engine was replaced at some point as well. But getting speeds up to 40mph have definately not been possible even with 1 person in the boat and trimmed all the way up to the point of porpoising. Once it does that, I back the tilt down a touch and it evens out and usually just barely gets 37 on the speedo. I have a GPS in the car so I think I'll take that with me next time and get an accurate reading. Maybe it is hitting 40 and I just dont know it. But the RPMs are definately at or around 4600rpm which on the engine block, it states is 4200-4600rpm for the max.

How do I find out the gear ratio? I've looked all over the place and I just cant find it anywhere. Every prop calculator I run into asks for it and I have 0 idea what to put for it, I dont even know what an educated guess at it would be to get something close.

I'm sure it needs a prop change, thats not really the question. But the question is, do I get the same exact prop, or should I get something totally different. I've been looking at the Propulse prop from http://propulse.jetshop.se/ but I dont know if it's something I should get or not. It seems to me like I could adjust this thing to whatever I need at the time. But I dont know how well designed it is, if it breaks a lot, how readily available the props are locally in the US, etc. I dont even know what size the prop should be to begin with or the pitch or any of that.