84 Force 125 Prop Selection

[ghstwlf]

Hi,<br />I'm brand new to boating and this forum and it's GREAT! I just purchased a 1985 Tara 16' open bow with a Force 125 on it. The Engine seems to start and run fine both at idle and higher RPMS. The problem is I guess I expected a little better performance out of a 125 HP engine on a light 16' boat. The RPM's max out at 5000 and my top speed is about 40. I've seen where other 16 footers with the same motor run out at 55mph. I have purchased new plugs and Mercury power tune for the carbs and I'll be draining the fuel and replacing it with fresh 93 octance and Mercury 2 cycle but I doubt this will make up the difference so am I looking at a prop issue and if so what do you think is the best dia and pitch for that combo? I've seen a 4 blade composite prop for a reasonable price are they worth looking at? Thanks for any help you can give me.

 

[kev_79]

Re: 84 Force 125 Prop Selection

Ghostwolf, I am sorry to tell you that the Force is unfortunately the black sheep of the industry. All other OB measure hp at the propshaft, while Force, up to the day they died, measures from the flywheel. So your 125 is equivalent to about maybe a 110 merc, evinrude, etc. That is a guess though, but it is significantly less. For example, I have a 18' bayliner capri with a 115 merc, and it runs about 43@5200 rpms. That is why the other 16 footers are faster. As for props, it sounds like since you are running 5000+ rpms you have the pitch right, but Force put some cheap props on their outfits, among other things. By the way, I owned a 90 model 90 hp force at one time. The oem prop isn't cupped, and has a straight edge. Better props are cupped and have a gradually increasing edge, though I can't think of the word they use for it. A better prop may get you a mph or so, but that is probably all that you can do with a 125 force on your boat. Good Luck

 

[ghstwlf]

Re: 84 Force 125 Prop Selection

Thanks. When I said another 16 footer with a 125 I DID mean a Force 125. I guess what I was looking for were the specifications of a prop that would give me the best performance from that size boat/motor combination. I Do realize Force rates their HP differently and I also know it's not a popular choice but I was attracted to how easy they are to work on with their simple technology. I also recall seeing somewhere that they should operate between 5500 and 6000 RPMs however my maunal has not arrived yet so maybe that is bad information.

 

[JB]

Re: 84 Force 125 Prop Selection

Ahoy, Ghostwolf. Welcome. Get yourself a cup of coffee. Go to the topic: "Hey, New Boater, Getting Started". When you are done, come back with whatever questions you still have.

 

[kev_79]

Re: 84 Force 125 Prop Selection

O I C, well then, I don't know. I have yet to come across a Force on any boat that would run 55. The best I have seen is a 125 on a 16 foot bayliner, and it ran out at about 44 by the speedo. It had a 21 pitch 13 1/2 dia, I think, on it running about 5400 rpm's, and I thought that was great performance for it.<br /><br />Keep in mind, their is no set chart for props and boat performance. You just have to try it out, and watch your Tach. Most people I have known, usually set the prop to bring you right under (100-200rpms) your upper limit, with a light load. This guarantees you won't over rev your engine under any conditions. <br /><br />I have tried the comprop, and I would recommend it, although I didn't keep it. It is really lightweight, and got out of the hole very well. The only downsides I could see is that if you did hit something, you would have to throw it away. Also, I thought it was ugly on my boat, but I trailer everywhere, and everybody wants their boat to look cool, right? But they are cheap, and short of hitting anything, I think will last longer and outperform any aluminum prop. At the price of the comprop, you could keep one for when you have a light load, and one for when you are carrying 4 people and pulling up a skier. Let us know what you decide. Good Luck

 

[ghstwlf]

Re: 84 Force 125 Prop Selection

Thanks however I read that prior to posting my question about boat length/horsepower/prop diameter-pitch. Pretty good information. I'd still love to hear some thoughts on my unrelated questions though.

 

[JB]

Re: 84 Force 125 Prop Selection

Hi, Ghostwolf. I'm confused. Nothing, of course, says you have to follow the advice you get here. That's up to you.<br /><br />I'll try again.<br /><br />Don't select your prop from a chart or formula. Select it on the water. If your current prop only allows you 5000 rpm and you want 5900-6000 go down a couple of inches in pitch and try it out.<br /><br />Don't use premium fuel. Use 87 octane, alcohol and lead free regular. <br /><br />Kev_79's advice is sound. There are 16' boats and there are 16' boats. Get your prop optimized, then wonder if your speedo is accurate and if the speedo on the 55mph boat is accurate. GPS is always accurate and usually comes in below hydromechanical units. It could be that your 40mph is as fast as the other guy's 55. There are about a dozen tips on getting top speed from your boat.<br /><br />Good luck getting the best prop for your combo. Let us know your results.

 

[sony2001]

Re: 84 Force 125 Prop Selection

GostWolf, Please try the higher octane to see<br />the effect on RPM.<br /> What pitch do you have, it's probably a 19"OEM<br />Your maximum is 21". WOT should be been 4500 and 5500 rpm. I'm running a 17" cupped after my 19"OEM and a 21"OEM. Soon I'll be trying a 4 bladed 19" Comprop. My impression is that the OEM's are not very efficient. {drag}<br />If you are using high octane the spark can be the OEM's recommendation of 32 deg.BTDC.

 

[RIDEPATE]

Re: 84 Force 125 Prop Selection

i just bought a hustler performance prop for my boat and it's my reccomendation from now on.wow.for the money it's worth checking into i bought a 15 degree and hub now a 17 is on the way and i've got less than 200.00 in two props!!!whadda deal

 

[Deerdog]

Re: 84 Force 125 Prop Selection

Hey Kev,<br />I willbe the first to agree that the Force brand isnt the best of motors but it came with my boat and I cant afford a merc....yet.<br /><br />My boat is an 89 model and yep i have rebuilt the engine once (in 94) and had a stator wire problem this year. Other than that now major problems.<br /><br />Im working on that 55 barrier though. My 150 Force will hit 50 fine now. The best I have had it was 53. Considering the Arriva boat is heavy (it is 19 feet) I think I am doing okay. I spoke with a guy who had the same boat but with a 22 pitch SS prop who states his would do 56-57 (that was on a Force 150 also). I am running a 21 pitch Aluminum on mine. The thing will cruise at 45 easily.

 

[sony2001]

Re: 84 Force 125 Prop Selection

My 21" OEM Force prop in aluminum is for sale. No nicks. I'm at {ndg2000@hotmail.com}

 

[ghstwlf]

Re: 84 Force 125 Prop Selection

Thanks for all the great info, I may very well look into those Hustler props. I swapped the plugs out last night and they were NASTY, also check the compression and they were all around 150 so I think it's a solid engine. I'll let you know what I get out of it once I run out the fuel and replace it with my own and run power tune through it.<br />Thanks again!

 

[kev_79]

Re: 84 Force 125 Prop Selection

Deerdog,<br /> I am running 44 with merc 115, wind behind me. What rpm's u running. 50 sounds good to me. The SS prop will give you a little more top end, but not that much, I don't think. Although boats are different, it sounds like you might be falling under what JB stated earlier. Speedos may be off a little. You could be doing a little better than 50, and maybe him a little less than 57. BTW, is that Force 150 a 6 cylinder. I had a 3 cylinder 90hp running 33 on an 18 footer so to me, 50 sounds quite well, considering the hp it takes to push a boat 5 more mph. Good luck breaking 55!

 

[JeffSlade]

Re: 84 Force 125 Prop Selection

I have a 17ft Bayliner Capri with a Force 75. I also own 2 Hustler aluminum props. I can run 35 with the 13 pitch at 5200 rpm. I could only run about 30 with the 16 pitch OEM prop. I would stick with the 87 Octane fuel and Walmarts' Supertech oil. Just about everyone here will agree with Supertech being just as good or better than most others. The CompProp is good until you hit something, then it's a gone. An aluminum prop can be repaired. Stainless steel will transfer the force of an impact to the lower unit and the gear box(bad news). Read many of 12Footers posts on Force, he is our resident expert on that make. He has some great maintenance advice.

 

[Deerdog]

Re: 84 Force 125 Prop Selection

Kev,<br />I forgot to put in the RPM's. It was at 5500 RPM when it hit 53. The hull was freshly waxed and boat stripped down. The Force 150 is a 5 cyl with three carbs. I agree with the SS prop giving more speed but not quite that much although he was running a 22 pitch prop as opposed to my 21 Aluminum. It is feasible considering the differences in props and perfect conditions. Honestly I believed him as he didnt seem the boastful type. The 21 is what is recommended for the boat/motor combo and does great. Yes the speedo could be off but that was all I had to guage it. <br />As for 55...I dont think so at this time with the setup I have. Now a Merc 150 with a 22 SS prop.........no problem. I do love the low end torque this engine has. I can pull two adult slalom skiers out of the water with a person in the boat. It also seems better on fuel than the merc.<br /><br />Deerdog

 

[ChalkBoy]

Re: 84 Force 125 Prop Selection

Well this is interesting. I too have a .....wait I am almost afraid of saying it....FORCE.... Anyway, mine is a '87 85hp, yes, 85 hp... I run it on a 16 ft glass bowrider. I have had it to about 40mph. The previous owner had it up to 45, at the right trim. <br /><br />I think there are several factors that come into play as to the performance of yur boat. However, I must say it can get rather difficult to get advice without the snarls at Force. Force is a pretty good motor if you are nice to them.

 

[manowar]

Re: 84 Force 125 Prop Selection

I have a 20 ft trophy bayliner and it weighs over a ton and a half easily with fuel 30 mph maximum 19 pitch prop dual carbs any suggestions other than get a lighter boat

 

[kevlar3000]

Re: 84 Force 125 Prop Selection

If you are looking for more speed, I don't think a 4 blade comprop is the way to go. You will likely drop a couple mph going to 4 blades. I just got a 21 pitch cupped Hustler and am not in love with it, performance less than I expected. I went back to the old 23 pitch uncupped quicksilver aluminum. I have a Merc V6 150 on a 1974 Glastron Carlson CV 16, with the 23pitch I hit 63 @ 5200 rpm. With the hustler 21 I hit 60 @ 5200 rpm. I had hoped for a few hundred more rpm with the cupped 21, but the cup is extreme enough that it held the rpms down. I got a lot more steering torque and chine walk<br />with the Hustler. I was a bit disappointed.

 

[Deerdog]

Re: 84 Force 125 Prop Selection

Hey Kev<br /><br />Tried again, with a very freshly waxed hull and a stripped out boat. It hit 54 and held, wouldnt go any further. Guess that is the max for me and this current setup - unitl next year when I get a SS prop in 22 pitch. Man I thought it was gonna do it. it did have over 1/2 tank of fuel in it though. will try again labor day weekend on funes and see what happens.<br /><br />Deerdog

 

[JB]

Re: 84 Force 125 Prop Selection

Y'know guys, I haven't seen an accurate pitot tube OR wheel type speedo yet that was within 10% of actual speed. The ones I have actually clocked were as much as 10mph high. That results in guys claiming unrealistic speeds (would you believe -5% slip?).<br /><br />If you care that much about numbers, get a GPS. They are accurate, unaffected by Bournelli Effect, vibration or any other disruption of accuracy.<br /><br />Red sky at night. . . <br />JB