Prop Advice for Merc EFI 115 on Malibu 182

[SteelyDan]

Try a powertech rbx4 stainless. There is an exchange policy so if your pitch is wrong you can return. I just bought a rbx4 for my 17 hourston running a merc 90 and the I originally ordered a 17p which didn't yield enough rpm so im currently waiting on the 15p replacement. Insane holeshot, cruise at a lower rpm and even picked up top speed.

Another thing you can look at with the props you have is motor mounting height. Raise the motor a hole and re test your higher pitch props and see how you like your results.

 

[MikePA]

Try a powertech rbx4 stainless. There is an exchange policy so if your pitch is wrong you can return. I just bought a rbx4 for my 17 hourston running a merc 90 and the I originally ordered a 17p which didn't yield enough rpm so im currently waiting on the 15p replacement. Insane holeshot, cruise at a lower rpm and even picked up top speed.

Another thing you can look at with the props you have is motor mounting height. Raise the motor a hole and re test your higher pitch props and see how you like your results.

Where is this that let's you return if the wrong pitch?

 

[SteelyDan]

Any powertech dealer. This time I used canada propeller but I have ordered through prop gods. I think there was a dealer on van Island but not sure about that anymore @MikePA

 

[Aquaholic]

Here are the specs for the 15” Turning Point 4 blade I am currently running.

 

[Macdeep]

Here are the specs for the 15” Turning Point 4 blade I am currently running.


View attachment 93074

And that’s on a 90?

 

[Aquaholic]

115. Replaced the 90 in December.

90 with the 2.33 leg used the 17”. 6000 rpm.

115 with the 2.07 leg uses the 15. 6000 rpm.

 

[Macdeep]

Update- the hydrofoil seems like the magic bullet for me.

Sticking with the 17 pitch prop and probably not going to bother with a 4 blade.

Hole shot has dramatically improved as has performance. Can get down to 4500rpm on plane for 18k with just me, and managed to haul 4 kids and 3 adults just fine planing at 5000rpm for 18-20 knots.

WOT is still way north of 6000, but I can live with it. Got her up to 33-35knots when approaching 6000rpm but the water wasn’t perfectly flat so it started to get a bit scary for me. I’m a max 20-25knot guy.

Best thing is, with two adults I don’t need to use the trim tabs to help with launch, just to level the boat.

And almost totally eliminates any porpoising.

Night and day. Performs like a different boat.

 

[Aquaholic]

They. Do. Work.
Great feedback.

 

[SpringVelocity]

Yes they work. Especially those hulls. Running with trim tab and the foil up on plane almost instantly. Zero porpoise. Of course hull extension changes it a bit vs this one.

Seeing your results at 35 knots at WOT makes me wonder still on my boat.

My 150hp gets that. I think I am maxed at 5700 with the 19p.

 

[Aquaholic]

Now that the hydrofoil has given you a great result, if you recall I shared my results that I reduced my minimum plane rpm by at least 400 rpm by going to a 4 blade (with SE 300). If you do ever try a 4 blade (pitch for pitch if Spitfire) you could go from 4500 to 4100 rpm to plane.

 

[Macdeep]

Now that the hydrofoil has given you a great result, if you recall I shared my results that I reduced my minimum plane rpm by at least 400 rpm by going to a 4 blade (with SE 300). If you do ever try a 4 blade (pitch for pitch if Spitfire) you could go from 4500 to 4100 rpm to plane.

!! Sounds like a good next step for me then!

I'm definitely more and more satisfied with the 17p 3 blade as I get used to trimming, but still want a bit more out of it, so ya, I think I'm sold.

Curious though if it's worth trying a 19p... or is that a step too far? Talking with a local shop and my mechanic and both were scratching their heads about the 4 blade and both suggested I try a 19p or even a 21p in a 3 blade... 21 seems a bit much though.

Currently seeing what my options are but no places in McNeill or Hardy are into letting me test before purchase which is a bummer. Might have to suffer through the season and then drag my boat to Campbell if there's a dealer/mechanic that offers the option to test props before buying.

If Amazon still offers free returns, I might have to go that route...

 

[Aquaholic]

With your high rpm at WOT, going up to a 19” is worth a try but your hole shot will suffer. Holeshot was one of your initial concerns.

 

[Macdeep]

With your high rpm at WOT, going up to a 19” is worth a try but your hole shot will suffer. Holeshot was one of your initial concerns.

Ya my mechanic thought I should think about going to a 14x17. Add some diameter to get the RPM down and improve whats left of the hole shot while maintaining my cruise speed, and stabilize it some what in chop etc.

Mid you, all my calculations are thrown for a loop because I still suspect my Tach is faulty above 3000rpm.

I entered my planned route for my trip on Saturday. Hardy to sutil, around Hope island and back to hardy. 27LpH at 5000rpm at 20 knots was supposed to be 82L fuel consumption plus a couple litres for trolling.

Filled up at the end of the day and it was only 60L.

Makes me think that when the gauge says 5000, it’s actually 4500, so possibly I’m propped just about right with a 17p. It still flips around without moving the throttle or the trim, it’s not often but sometimes it surges to 6k and the creeps back to 5k when I’ve been on plane for a bit and have things trimmed and good.

Time (and $) will tell I guess. Gotta get my tach checked during a water test this fall once my mechanic isn’t so busy, and find a shop that lets me water test a few props… hard to find up my way. I guess I can abuse amazons return policies!?? See if I can order a half dozen props, pick the good one and send back the rest?

At least I got my kicker to troll nicer. I think I passed carb cleaning 101 so that’s good.

 

[Aquaholic]

Another concern raised from your first post was that your tach was not reading properly, and you replied the mechanic tested it and said it was alright, but now you do think it is off? I would consider the tach accuracy as the baseline requirement for any testing, so hopefully that's an easy fix and then you can continue tweaking.

 

[Macdeep]

Another concern raised from your first post was that your tach was not reading properly, and you replied the mechanic tested it and said it was alright, but now you do think it is off? I would consider the tach accuracy as the baseline requirement for any testing, so hopefully that's an easy fix and then you can continue tweaking.

Yep- a few things to sort out.