Proper prop and pitch

[frizzy]

Hi all, I have a new to me 18.5 campion explorer 542 with a 1995 merc 125 2+2. Just wondering if anyone has a similar set up and what type of prop and pitch you are running? I recently took it on a trip and couldn’t get it to plain with two adults and 3 small kids on a tube.
Thanks!

 

[chris73]

Hi all, I have a new to me 18.5 campion explorer 542 with a 1995 merc 125 2+2. Just wondering if anyone has a similar set up and what type of prop and pitch you are running? I recently took it on a trip and couldn’t get it to plain with two adults and 3 small kids on a tube.
Thanks!

I'd start with a 13 3/4 x 17 prop and then fine tune from there.

 

[1marko]

Hard to say without knowing what's on there now.?

 

[CIVANO]

4 blade gets you on plane much quicker and at a lower speed than 3 blade but decreases top speed.

 

[Old Fisher]

Agreed. 4 blade. What you may lose in top speed (1-3 mph), you will more than make up for in cruise efficiency, load carrying capability, etc

 

[frizzy]

Thanks guys! It came with a mercury high five 5 blade 20p Witch after running for 10 min realized it was for slow big wake water sports. I switched it with my spare prop 19p 3 blade. Better but not great.

 

[Sentinel]

With the load you expect to be carrying most of the time you should be able to reach max rated rpm of the motor at full throttle, or within a few hundred rpm’s anyway. If you cannot, you are overpropped and overloading your motor , which will get you substantially less service life.

 

[beemer]

by my calculations you should be doing 30 plus knots with the 19. Are you sure it is switching over to the 4 cylinder mode? beemer

 

[frizzy]

As far as I can tell all 4 cylinders are firing.

 

[beemer]

as my wife often says "you may need professional help"

 

[calmsea]

For that motor size you are over-pitched. As chris73 said, try a 17p.

 

[Wwunder]

I have a malibu 185 with a 150 hp and run a 19" pitch (4 blade aluminum). My friend with a malibu 182 and a 115 hp runs a 15" pitch (stainless 3-blade). I think the 17" pitch is good advice to start out... Pulling tubes and skiers is hard work.

 

[Old Fisher]

Keep in mind that the correct prop for your boat depends on several factors. It's not as simple as "x amount of horsepower means I need ____ pitch. Boat motors have different gear ratios. Props have different blade designs, blade areas, blade diameters etc. As an example: A 15 1/4 x 17 P four blade prop is a very different animal than a 13 3/4 x 17P 3 blade. Even props with the same number of blades can be very different.

 

[Wild Bill]

Thanks guys! It came with a mercury high five 5 blade 20p Witch after running for 10 min realized it was for slow big wake water sports. I switched it with my spare prop 19p 3 blade. Better but not great.

So the basics are higher pitch more speed if you have the hp. So your 20" pitch is for a higher speed lighter boat. 17" pitch good start.

 

[Pineapple Express]

FYI, those High Five props were the go-to prop in the 90s for top speed and bow lift. It's definitely not a prop for a heavy slow wake boat. Regardless, with "only" 125hp on an 18ft family boat you need something with less pitch and more blade area to get that boat moving. Look for props that have stern-lifting characteristics....often 4-blade props do this.

 

[Wild Bill]

I had a 16 1/2' deep v with a 115 merc "tower of power" we used for skiing and awesome out of the water, shot straight up with a ski bar and popped us out nice. Actually hull would slam down and ended up with two 4' long breaks along the lift strakes under the driver, big leak! Rebuilt the hull with new stringers and added a dole fin and it tamed it down. It would pull like crazy and top out at 43 mph allowing me to barefoot.

 

[David Hall]

As sentinel has pointed out, your first concern should be reaching your engines peak RPM at W.O.T. Or as close as possible, engine manufacturer provides the recommended peak RPM to shoot for and if you are running more than 150-200 RPM below this you are overpropped and risk shortened engine life.

 

[Island Fish Lifter]

13 1/4X 17 aluminum is the prop you want. I have the same boat.

 

[Prfisher]

My 19’ Livingston Viking came with that same motor. It had a 13 1/4 x 17P on when I bought the boat, but would over rev badly if I let it. I installed a 19P 3 blade aluminum & problem solved.
My boat is likely a bit heavier than yours (around 3,000 lbs. full fuel & gear) & there was power to spare, getting up on plane & at cruise.
From my brief experience with this motor (I used it for 1 1/2 seasons) I found it to be very powerful & reliable.
I replaced it because I couldn’t stand the rough idle (running on 2 cylinders up to about 1700 RPM) & the mess & stink of a two stroke.
If you aren’t seriously overpropped, I would do a compression test & confirm that it’s firing on all cylinders at high power.
One day I was out & the performance was poor. Very slow out of the hole & at WOT. Turned out one plug lead had fallen off. It ran surprisingly smoothly on three cylinders.
Just one guy’s experience, FWIW.