Mercury 115 Propping help?

[100333624]

Hello friends! We've picked up another boat, a 1991 Campion Explorer 19' with a 1991 Mercury 115hp. You can see the stats for the boat on the iboats website posted below. It weighs 1700 pounds dry. We were 4 adults and gear (800 pounds), with a full tank (140 liters) and a spare optima battery (50 pounds?) With this 115 4cyl Mercury motor we were clocked at 51 KPH on GPS at WOT but she was turning 6000 RPM. We are looking for a better prop to hit the optimal WOT RPM range which I believe is either 5500 or 5750 if anyone can confirm? The prop we are currently using is the original 19 pitch aluminum prop. Plans in a few seconds and runs pretty good. We always fish with 3 or 4 guys so we are usually loaded. Looking for something to give a better overall performance, what do YOU guys recommend?http://boatspecs.iboats.com/Campion_Marine__190_Explorer__1991/bp/66b13320

 

[wired247]

Re: Mercury 115 Propping help?

First things first. That prop is horrible. You are going 51 KPH (30 ish MPH) at 6000 RPM with a 19 pitch prop. I dont doubt that because I have used those aluminum Merc props before and had similar horrible prop slip numbers. Yours is in the 40% slip range. Awful. If you had a "good" 19 pitch prop you'd be more into the mid 50 Miles Per Hour range. In any case absolutely do not use the numbers you get from that prop as a baseline for deciding on a new propeller.

My recommendation would be a 17 pitch Solas stainless Titian 4. It will get you to 45-50 MPH with a great holeshot and put you in the high 5000's. The Solas Titans have a heavy cup and that 17 pitch number should be taken with a grain of salt. Its more like a 19-20 pitch prop.

 

[Dave1027]

Re: Mercury 115 Propping help?

Hello friends! We've picked up another boat, a 1991 Campion Explorer 19' with a 1991 Mercury 115hp. You can see the stats for the boat on the iboats website posted below. It weighs 1700 pounds dry. We were 4 adults and gear (800 pounds), with a full tank (140 liters) and a spare optima battery (50 pounds?) With this 115 4cyl Mercury motor we were clocked at 51 KPH on GPS at WOT but she was turning 6000 RPM.

51 kph is only 31 mph! Your prop must have issues like maybe a spun hub? A 19 pitch on that motor doing 6000 rpm should be close to 50 mph. I know your boat is big and heavy but that's some serious slippage. +1 to what Wired posted. SS is the way to go.

 

[100333624]

Re: Mercury 115 Propping help?

Thanks for the response guys! I don't understand how the hub could be spun because I took it to my dealer and he said its perfectly fine. It looks ok too nothing wrong with it? It's a square hub and fits snug in the prop... How can I tell if it's spun?

 

[wired247]

Re: Mercury 115 Propping help?

Its probably not spun. Those old OEM merc aluminum props just suck. Tried one on my boat once and it went 35 MPH. Its normally a 56 MPH boat with a good 19 pitch.

 

[100333624]

Re: Mercury 115 Propping help?

Thank you wired247 for your input! It just so happened that there was the EXACT prop you mentioned, a brand new Solas Titan 4 17" pitch prop for sale with a Yamaha hub that just so happens to fit my 115 Merc! I will have it out for a water test by this weekend and let you know the results!

 

[Luckymann77]

Re: Mercury 115 Propping help?

I have been wanting to re-prop my 77 1150 as well...
Currently have a Quicksilver 23p which is WAAAYY too much prop for it and My 83 Hydra Sports Bass Boat...

Anyone have any thoughts on one of the Solas in a 4 blade aluminum ???
Can't spend 300 smackers on a SS one...DANG IT !!!

Waiting to hear from you 100333624 on your next outing with the new prop !!!:joyous:

Thanks,
Luckymann77

 

[wired247]

Re: Mercury 115 Propping help?

I have tried one of their 21 pitch 4 blade props in aluminum. 7% slip in my boat with a 140 Johnson. Didnt go any faster than my old 19 pitch OMC prop. Wasnt that excited by it. After you use one of their titan 4 props its hard to use much of anything else as a multi duty prop.

 

[Luckymann77]

Re: Mercury 115 Propping help?

Hey wired,
Thanks for the input...
Does Solas make an aluminum version of the Titan???

And...
How does one measure 7% slip???

Sorry if this a newby question...
Mine feels like 40% !!!

Maybe I just haven't gotten it to a big enough lake to get it a wound up???

23P seems like a lot for this motor or am I mistaken???

Thanks,
Luckymann77

 

[wired247]

Re: Mercury 115 Propping help?

Prop Slip Calculator | Propellers | Mercury Racing

23 pitch is too much for an inline merc on anything bigger than a small race boat. I'm surprised you can get that thing on plane. In any case you don't have the power to push a 23 pitch prop with a relatively heavy bass boat to its full potential. You'd go just as fast with a 17-19 pitch and have a much better hole shot.

Aluminum props are machined differently that SS props. The blades can be thinner on stainless and are usually more efficient. Ive owned half a dozen of the SS Titan 4 props in different pitches. Their advertised pitch is usually bogus as their slip numbers are too good to be true but they pull great and have decent top speeds. For example I can go 60 MPH ( GPS ) at 6100 RPM with my 19 pitch Titan 4 on a 2:1 lower. Do the match and you will see that is impossible. That 19 pitch is probably actually more like a 22 pitch. Still pulls hard and runs great .

 

[jestor68]

Re: Mercury 115 Propping help?

The WOT rpm range for the 1991 Mercury in line 4 cylinder 115 is 4750--5250 rpm.

 

[jestor68]

Re: Mercury 115 Propping help?

Your weight calculations left out the weight of the motor(1700 is just the boat). The dry weight of your boat/motor is about 2075(not accounting for any wet foam).

The Merc prop selector comes up with a 13 X 19(al) or a 13.25 X 19 Laser II and says you should be able to do about 39-40 mph(8-10% slip) at about 5000 rpm.

If you are turning 6000 rpm, I'd suspect the prop hub or the tachometer's accuracy.