Prop Question

[SimilarIsland]

I have a Lund Outfitter 1750 with a 90 Opti. It came with a 12.75 x 21 Prop. The max rpm on the motor is 5750 and my Wide Open Throttle is 5400 with a top speed of 42. I asked my dealer for a prop today to give me a bit more hole shot for skiing and he gave me a 13 x 19. I understand the 19 should increase my rpms by about 200, but how will the larger prop effect performance? When I plug in all the variables into the Mercury HSOforum, it tells me to use a 13.25 x 17. These are all aluminum props.

Thanks

[Ralph Wiggum]

I don't think those minor prop diameter differences are going to make much of a difference at all. A 21" pitch seems a bit steep for that set-up (especially considering your RPMs). I'd try out the 19", but if you're looking for hole shot for skiing, I think a 17" would be better. SS would be best, but they're a lot more money.

My M-I-L has a Alumacraft Competitor 170 with a 115 Johnson on it. I've got a 13.25" x 17" stock Evinrude/Johnson aluminum prop on it and it pops some decent size skiers out of the water pretty well. I'm about 235 and have no problems getting up on two skis. One of my brother in laws is about 210 and can get up on one with some patience (plus he's a better skier than I).

[wakeguy]

I think you may actually see a greater RPM increase than 200RPMs. We often see 200RPMs per pitch given the fact that you are using the same brand and model of prop. There are many more factors aside from pitch and diameter including rake and cupping so if you change brands of props you are basically starting from scratch. Your other option is to switch to a 4-blade prop; Mercury offers one although it may be made under the Quicksilver name. If you decide to run the 17 pitch prop make sure you are watching your RPM's at WOT and make sure you instruct anyone else who might be driving your boat that they can't run it wide open.

[SimilarIsland]

Thanks guys for the input.

I guess I'm kinda hoping that the increased wicth of a 13.25 x 17 would keep me under the 5750, but maybe I'll only be able to go to a 19 pitch. Even the 21 is not that bad. My son is about 240 and I can pull him up on two pretty well. But I'd really like to get him up on one - which pulls pretty hard.

[Ralph Wiggum]

which pulls pretty hard.

Tell me about it I'll do it this year!

[marine_man]

Dropping to the 17 is going to put your RPM's at Wide Open Throttle over the 5750 without a doubt...

The 19 will be borderline, but I'd definitely try it.

marine_man

[dan z]

the 17 will make your boat jump out of the water but you will loose top end. a 19 is going to be the best all round pitch. and like you have stated the 21 is just a dog out of the hole but its the fastest of the three.. we have a 19 and a 21 and use the 21 up north and the 19 around here

[mamohr686]

You should step up to a 4-blade trophy prop or a new 3-blade fury if they make it in 21 pitch. The stainless mercury props have an interchangeable vent system that allows exhaust gasses to vent over the blades and bring up your rpms while getting up on plane. When your getting up on plane your rpms should be able to hop up to about 3500 or so without slipping too much. The fury is a lot more expensive because it is a thinner, lighter, composite metal that is stronger than SS props. You can get any stainless prop from kenyon power boats in FL (with the exception of the fury) for $400 and they will exchange it if it's not right for your rig. That's way cheaper than any boat dealer im MN will sell them for. They have a HSOforum so google it and talk to one of their prop experts, you won't be dissapointed.

[Ralph Wiggum]

Dropping to the 17 is going to put your RPM's at Wide Open Throttle over the 5750 without a doubt...

The 19 will be borderline, but I'd definitely try it.

marine_man

Oops, I was thinking 200 RPMS for every 2" in pitch you drop. It's really about 200 RPMs for every 1" in pitch, correct?

It's definitely worth buying from a dealer that will let you try out a few props to see what works. There's just too many variables involved.

[SimilarIsland]

Thanks Guys for all the great advice!

[marine_man]

Oops, I was thinking 200 RPMS for every 2" in pitch you drop. It's really about 200 RPMs for every 1" in pitch, correct?

That's correct...

marine_man

[MEGASLAM]

Is there a place a guy can find one of these dealers in the east metro that will let you try out a few props? I want to experiment with diameter, in order to get a nice stable plane at lower speeds, without adding to my prop collection.

[marine_man]

You'd have to call and find out. They'll usually hold your credit card, or "sell" you the prop, and if you bring it back in the same condition it left in they'll let you exchange it.

marine_man