Prop suggestions

[SkiDad]

i have a 19' boat with a Force 125. My lower unit was swapped to 2:1 ratio. Typical load is 2500 lbs. We setup our boat to pull hard for skiing.

Anyhow with my 13-3/4 x 15 Michigan stainless prop I average 36 @ 5200. The prop is cupped but not a lot and while it takes off great it does't corner that well. I can blow out very easy if I gas it when turning to retrieve a skier. I don't trim up much - at most 20%. My AV plate is level with bottom of boat.

I just threw on my Hustler 13-3/4 x 15 aluminum props for kicks this weekend (only used it a few times in the past) ... while it doesn't have quite as much hole shot it held a TON better in turns. 38 @ 5100. The prop probably has twice the cupping the SS prop has and acts like a 17p for numbers.

Anyhow what are your suggestions for props - i can only fit props that are a universal fit like Michigan or Turning point, probably Solas and some Power techs (with removable plastic ring and square hubs). I was told the Power Tech NRS3 would work for me but it shows a ton of cupping. I also was looking at RED3 (less cup) and a New old stock Michigan Rapture.

I understand propping rpm very well I just get lost in the science of all the cupping, rake, etc. My boat is not a go fast boat.

my concern is hurting my slalom hole shot which is great right now.

 

[alldodge]

my concern is hurting my slalom hole shot which is great right now.

My suggestion is to keep what you have and use your thumb more. Depending on speed I have blown the prop out a tad, so when I start my turn I trim down a bit and once straightened out, trim back up

 

[steelespike]

I'm thinking maybe you could ventilate the Hustler.It is said to improve holeshot without affecting top end.
Maybe a 14" Hustler. Maybe a 14" 4 blade?

 

[SkiDad]

Good thoughts, my lower unit is not thru hub exhaust even though I used that type of prop - the exhaust exits a snout. As for trimming i set it at the beginning of the day and don't touch it b/c it's on the dash vs on the throttle - i pretty much set it perpendicular to the water at the dock. But even if i go all the way down it will vent about the same - i think that stainless prop is just not a good gripper in the corners.

 

[GoldDuster360]

We did allot of skiing behind a 23 Mako with a 225 Evinrude. It spun a big cupped stainless prop and we used the trim liberally. Typical launch prodedure was:

Trim down for maximum holeshot and then trim up once the skier was out of the water and the boat was on plane at our desired speed. We had to make some fairly tight turns on the ICW down on west palm area so when we were ready to turn around it required a fair amount of trim down to avoid ventilating the prop and knocking the skier off the top of the water. Our boat had a trim gauge so we had a point of reference for launch, plane and turning.

My boat that I have now has manual tilt/trim so prop selection and boat loading is critical. I recently purchased a prop in stainless because with few exceptions stainless props generally have more cupping as the metal accepts it better than most aluminim alloys. I lost 150rpm's on a heavily cupped prop with progressive pitch. Ventilating was greatly reduced.

You are going to lose some rpm on a more aggressively cupped prop. How much depends on how much cupping your current prop has. I would go down in pitch one number for a prop with cupping that grips like your Michigan prop in an effort to maintain hole shot. This is just my opinion.

My final vote however is with Alldodge: Use your thumb more

 

[Frank Acampora]

Sharp turns will make the prop ventilate. How much depends upon the prop design. You do not have the option of a vented prop. At this point, your choices are limited. Why not try moving the trim switch to a more accessible spot? Tuck in the engine for turns and hole shot. The switch can be in parallel with the existing dash switch. Buy a single or double pole MOM switch from Radio Shack or other electronic suppliers.

Another option that costs more money is to replace the 2 to 1 lower unit with a 1.95 to 1 dual exhaust lower unit. Then more props are available and you can vent them. However, depending upon the year of your engine you may need to cut some metal out of the cross web to allow clearance for the larger Mercury water pump.

BTW: I have a 150 with dual exhaust on my 21 foot cuddy cabin. The prop is a 13 X 19 stainless vented. It gives good performance but I can not trim up more than about 1/4 of travel otherwise the prop ventilates. I believe it is the design of the hull bottom that causes this. I went to all the bother and fuss of cutting down the transom by one inch and it did not help.

What I am saying is that depending upon your hull, you may always have a ventilation problem no matter what you do.

 

[SkiDad]

so i sent my stainless prop in to a shop to be cupped more and they call me and tell me my blades are out of pitch - one is 14.75 one is 14.6ish and I forget the other one. The prop is supposed to be 15 pitch. They seemed to think that this could cause my venting issues. I only paid 70 bucks for the prop and i don't notice any vibration - would this repair be warranted or would that be a waste of 160 bucks ?

 

[steelespike]

It's a relatively straight forward procedure to repitch a prop. That's assuming it hasn't been stretched out of shape.
If you want stainless this may be the only way out. Frank can probably give you an idea whats out there for A Force.
I don't know the details but I think some thru hubs will work on your motor.

 

[Frank Acampora]

Awwww! The prop has probably been lightly hit or driven through sand a couple of times and the blades bent a little. BUT---Why spend 160 to re-pitch and cup it when you can spend about the same amount on a good used prop? If it is not giving you trouble keep it as a spare.It is the end of the season. Use it until you find a suitable replacement.

 

[SkiDad]

So I decided to have them fix the prop. I'm very happy with the results. The Hale MRI report I got back showed the blades were 14.77, 14.37 and 14.69. Effective pitch of 14.6. They returned the blades to 15 pitch and did some additional cupping. Cupping made a huge difference in the turns. Rpm on top is the same. Cruise is about 1-200 less. Now the boat ride noticeablely higher out of the water - which in turn made my slalom wake softer !!!

 

[Frank Acampora]

Looking back at your original post, I forgot to mention that if you have a 2-1 ratio lower unit you are NOT limited on prop selection. You merely need to get a little creative. If you search my past posts of more than a year ago in both the prop forum and Force forum you will find how I modify both props and the lower unit. For example: I modified the mounting and thrust washer to accept a high rake fully cupped Ballistic prop. This allowed it to clear the exhaust snout without grinding away any of the snout. Since you do not have dual exhaust, many other props can be used simply by cutting away the rear flange. On aluminum props, just for aesthetics, I cut and glue the flange back inside the prop outer hub.
If by chance you do tear the gears out of the 2-1 lower unit, a 1.93 lower from 1989-1993 Force will fit and give almost the same results. The advantages are: Stronger gears and a better/bigger water pump. You can get either a single exhaust or dual exhaust. Both have two piece drive shafts. Since the water pump housing is larger you may need to cut a little metal out of the cross web inside the mid leg.