Prop selection

[Javelinman]

I have a new aluminum mod-v bass boat with a Merc 150pro xs. I have a 19p and 21p tempest. With talons,electronics and gear I run a little heavy. My problem is my 19 can cause me to exceed 6000 rpm and my 21 runs about 5600 while solo at WOT. While I know it’s not a speed demon and never will be I still want to be at the upper end of operation range while solo. My thought is to try a 19p revolution 4 as mercury states a 4 blade robs 50-100 rpm’s. It’s like the perfect prop would be a 20p tempest which is not made. I spoke with Phil’s prop and it’s not recommended to try to reshape my 21. I’ve also have spoken with a couple places that claim these new 4 strokes are a bear to prop. Has anyone had any experience with the Revolution 4 or does anyone have any other recommendations. Thanks.

[TonyM]

I would probably get a 2nd opinion on re-working one of the props if that’s what you want to do and it would get you into the RPM range you’re looking for. 1st I’ve heard of a prop shot not wanting to re-work a Tempest.

[monte300]

I also recommend a second opinion on reworking your prop. When I got my new Triton TR19 with a 175 Evinrude back in 2000 it came with a 25 pitch four bladed bass prop. I could never figure out how to keep it from chine walking at WOT. I had that prop worked down to a 23 and I love it. This was never the fastest boat on the water and I happily traded a couple MPH on the top end for better hole shot and mid range responsiveness. I think the rework cost me $200 or $250 which was better than $600 for a new prop.

[WRB]

Contact Phil’s Prop Shop in Redding and discuss your situation. Phil’s has loaner props to try and reworks props.
Fury 4 blade 22P may work for example, better hole shot and may hit your 5800 rpm target.
Tom

[BIG DADDY BLUE RANGER]

The Merc 150 Pro XS 4S has a 2.08 gear ratio (like the Suzuki SS) which makes finding the right prop a little more difficult.

Of the two props you have now, which gives you more top end speed? Either way the 19 is definitely to small if you're getting to 6200 rpm but it's good to know... the motor has an overrev at 6100 if you're there for more than 10 or 20 seconds...not good

Do you get decent hole shot with the 21?? If so, 5600 is in the correct operating range (5500-6000). The only advantage to getting closer to the upper end of the operating range is quicker acceleration but that doesn't necessarily mean higher top end speed. You have to experiment with props to find which gives you decent enough hole shot plus the best top end speed. How does the 21 perform with a full load? Are you still getting at least 5500 rpm? If so I'd leave it alone

I have a 150 Pro XS 4S on a ranger hull and run a 25P Fury 3 and under light load will get 5900 rpm. I don't have any experience with aluminum hulls (some have a pad design and some don't) but I can't imagine there's that much difference in performance compared to your numbers (maybe there is IDK). I'm obviously running a much larger prop and getting higher RPM which seems really odd to me but who knows. When you say WOT do you mean WOT AND fully trimmed out? If you're not fully trimmed out (or don't know what''s considered fully trimmed for your boat) your RPM numbers will be way too low and you can't determine the right prop until you know what you're really working with. If your engine is mounted too low that will rob you of performance too.

Also, when comparing a Tempest to a Fury 3, the comparable Fury will be one pitch size smaller because it has longer blades. So a 24P Fury compares to a 25P Tempest etc. The advantage of a Fury would be that it's a lighter weight metal and has a smaller hub diameter so it will give you better hole shot over a Tempest. The Tempest is better for carrying heavy load boats...... for example, I can turn a 26P Tempest on mine and get similar top speed but it really struggles on the hold shot so the Fury is a better choice for mine. I don't know if Merc make a Fury in the 20P size though

I would definitely not run a 4 blade on your boat. An aluminum hull is pretty light already and probably doesn't need additional stern lift

[Javelinman]

The 21 has better top end and still a fast hole shot. I have a jack plate and best performance is with vent plate an inch and a half from bottom of hull. This is not a pad boat. Never thought it would be fast and these hulls don’t lift. Sort of just skip on the surface. Too much hull in water to be very fast. With the 19 at 6100 I hit 51. I’ve hit 53-4 with 21p. Both at full trim. Depends on lake. Lose about 1 mph with buddy in boat. I also porpoise if I reduce speed too much. My thought is that since the bow doesn’t lift much I might benefit from a 4 blade as I’d get more stern lift and probably reduce porpoising. The Revolution 4 has multiple pitches. In theory a 19 4 blade should lose 100rpm off my 19p 3 blade putting me at 6000. They have a 20p so I should lose another 200 rpm putting me at 5800………. In theory. I switch to aluminum since it was the biggest boat that still fit in my single car garage and the massive front deck and huge rod locker. Knew what I was getting into. I just want to have enough rpm so I don’t have to keep changing prop every time I go to higher altitude lake. My last trip to clear lake I was about 5400 rpm. Operating range 5200-6000. Thanks.

[BIG DADDY BLUE RANGER]

Boatmasters has loaner props too if they’re closer than Phils. May just need to experiment a bit and see what’s best. You could always have your 21 worked down a tad without reshaping it so it’s closer to 20.5 or even 20. Before I switched to lithium batteries I used to switch down to a 24p Fury 3 when going to Clear Lake tournaments from the Delta during the hot months because of the elevation change….. it’s not that much but it’s enough to alter performance about 200 rpm for me. Good luck

[monte300]

My understanding is a prop can be reworked two sizes either direction. A 21 can be worked to a 19, 20, 22 or 23

[LEN B]

Try these guys. Len
http://www.marksprops.com/

[Jboutfishn]

Phil's has resized SS and aluminum for me. They took a 21 SS down to a 20 and a 21 Aluminum down to a 19.