Need advice on more aggressive prop for my situation

[Maclin]

On my boat the 21p basic aluminum will not hold when cornering or even going straight in rough water, or at trim much over 1/4 on the gauge. I know now it is the wrong prop after some research on this size and brand of boat (the one in my sig). I can even get it to blow out on a holeshot if I have the trim up even a little, not even to the 1/4 mark. When I am cruising at about 3k rpm trimmed up and nail it all the way the prop spools up and then the boat speed catches up in a couple of seconds. Slip calcs are not good.

It had a High Five 19p on it when I bought it, all vent plugs were in. First time I took it out I got it to overrev, kinda freaked me out. It accelerated well. I was just going to try to get used to the potential overrev, but didn't like that and figured I needed a prop change. It also felt odd in reverse as well, had to give it a lot of throttle before it would move. Just not used to that feeling. So I sold it and got the 21p alum. Even though the engine is just under max RPM's at WOT, this was a BAD decision.

Now I want to fix all this with a new prop. Short list is...:

• Enertia 20p
• High Five 19p
• High Five 21p

All of those are vented.

No budget for expensive prop-swapping supertune effort this year, so maybe the known entity, a High Five 19p is best "economcal" choice. Not sure if going to a 21p on the 5blade may be too much. I like the Enertia because it seems to be an aggressive prop with the rake needed and is available in the one inch pitch increments. I do not know how it compares to a High Five. BTW: Do all of these feel weird in Reverse? or is that just me!

Any experience with this situation? Thanks in advance.

Engine..........: 4.3MPI
RPM range...: 4400-4800
Current prop is Michigan Wheel 21p Aluminum Vortex
Current WOT RPM...: 4700
Current top MPH is about 45
I also have a 19p Merc aluminum and it can overrev. Hits about 45 also.

Original baseline recommendation from Bryant for this boat in 2002 via brochure and owner's manual was a stainless Vengeance. Next up was a High Five. No pitch was mentioned. Further research shows the boat responds best to props with more rake for the bow lift, again this is from reading about props and also testimonials from Bryant owners. Fuel tank is in the front, and the hull has the extended planing surface in the rear. Outdrive seems to be a little higher than some/most. From the evidence, a stern lift prop is exactly the opposite of what the boat's configuration dictates.

 

[WesNewell]

WAG. Hub kit slipping? Is prop vented? Install vent plugs.

 

[jimmbo]

It is well known that I like the Enertia and that’s what I recommend. The Enertia has lots of rake and can lift the entire boat vertically out of the water, not just the bow. It also has a tenacious grip on the water. I did vent mine using the smaller of the medium sized vents.

 

[Maclin]

Thanks jimmbo . Any idea about the pitch for the Enertia, based on a high5 19p that could overrev at normal loads?

 

[porscheguy]

I’d opt for the 19P Enertia. They run heavy on pitch, and iirc, you’ve got a 1.62 ratio. You’re not making 4800 with your current 21p aluminum. But you are making 22% prop slip. That’s high for 19’ runabout.

A 19P Enertia, 1.62 ratio, @4850rpm or so, going 50mph is a slip of 7%. This is well within reason.

And dont ignore the quicksilver q3 at $450 vs the Enertia at $700.

The extended planing surface is like having fixed trim tabs. They’re good for reducing bow rise on acceleration, but they also limit the function of the outdrive trim.

 

[Maclin]

Thanks porscheguy what I wanted to find out about the Enertia, tends to run heavy on pitch. Yeah, ratio is 1.62, left that out up top there.

On the Q3, looks like those are not vented?

Thanks again, y'all are the best.

 

[porscheguy]

Those aren’t actual pictures of the prop, they’re illustrations, and the illustrations aren’t always accurate. Even mercury doesn’t spend much time keeping the Quicksilver site up to date. They are vented. Says so in the paper catalog.

With a 1.62 ratio I would stick to 19P on any stainless props. If you search through old threads, you’ll see plenty of 19-20’ runabouts with 1.62 gears and either the 4.3 or the 5.0 and 19P seems to be the limit on pitch.

 

[Tail_Gunner]

Ive experienced this a bit with a old stiletto 4 blade with vents, I always ease a boat up on plane, once there I trimmed and off to the race's...well kinda she would always blow out under full power, I would have to lower the leg again to power up until 40 then go to full trim. As time went on I found there was a trim level for different speeds, I acutally had a lot of fun hitting it hard at 35 mph, she would spool up (slip) for a fraction of a second then catch or hook up. It would pull like the secondaries had just opened up on a big block carb engine of old. In the end it was just the rake of the prop combined with the nature of the hull, it would literally lift the boat ...leg right out of the water. The was no set trim level for continuous operation perhaps as many a 4, part of the whole combination. At high wot I believe she raised as much as 10" out of the water. With that said your cav plate sets where in relation to the bottome of the keel. The barrel of the prop is it flush to the drive. I have some pics of the lift somewhere PB cut me off of the old one's. I only bring this up due to a high five losing grip that's way wrong its something mechanical in nature...lol I think.

 

[Maclin]

I did not experience blowout with the High5. Replacing it was a bad move on my part.

 

[89retta]

I know when I tried a High five 21 pitch I could hit the rev limiter. Same engine as yours but Volvo.

 

[jimmbo]

While the High 5 and the similar QST 5 have five blades, the blades are smaller. They also have a progressive variable pitch and rake. The smaller diameter of the High 5 effectively puts the tips of the blades quite far from the bottom of the AV plate. I often wondered if an engine spinning a High 5 could tolerate higher transom heights more easily. The blade shape itself looks like it should be able to handle some surface breaking

 

[Maclin]

Yeah, the blades are small, and it had no grip in reverse, just felt weird. It was probably one of the 2 best props for this boat, sigh.

 

[jimmbo]

Yeah, the blades are small, and it had no grip in reverse, just felt weird. It was probably one of the 2 best props for this boat, sigh.

Once you try an Enertia, you will know what the best prop is

 

[Maclin]

Hey Guys,

I looked at all this again, and am taking some advice that I would have given this guy...!

I am going to do a reset, and put a (used) 19p High5 back on it. It is the recommendation from the factory, albeit in 2002. The one that came with the boat when I bought it had obviously been on there a long time, I know they slalomed a LOT. Perfect condition, just dull from living in the water where it was stored.

I did not exercise my original one much at all, just one session for about 1.5 hours. It went pretty good, but I did not like how much throttle it needed when reversing, and it overrevved right at full throttle. Light load, but I really did not like the amount of throttle it needed when reversing, just thought something was wrong with it I guess. From inter-webbing, I have seen where that is a very common complaint with this prop. If all else is good then most just live with the (lack of?) performance when backing up apparently.

I will run it through the gauntlet and make notes. Then, having a better understand of strong and weak points, will reach another decision point with much more realworld performance data.

Thanks for the input, very much appreciated. Prop should be here soon, looking forward to wringing it out.

 

[89retta]

Maclin I too have been playing the prop game. When we first got the boat it came with 17&19 SS Volvo props both would hit the limiter. Tried a 21 High 5 and could also hit the limiter. Then I purchased a Apollo 4 blade SS 20" decent hole shot and could hit 50mph at 4700 rpm Best prop I've had till I dinged it on some rocks. Due to finances started a search for replacement aluminium. Got a TP 4 blade 19 and it performed pretty close to the Apollo. 47 mph at 4800 rpm and good hole shot. But like many kept searching for the perfect prop. Tried a stock Volvo 21 hole shot suffered and same speed. Tried a TP 19" 3 blade great hole shot but hits the limiter. Picked up a Rapture SS 21 poor hole shot and slower then the TP 4 blade 19. Just picked up a Solas SS 4 blade 19 and waiting to try it out. Will let you know how it works out.

 

[Maclin]

Thanks 89retta. Does yours have the 1.66 or a 1.79 ratio? This Merc I have is the 1.62, seems to affect me more than I like. I have a couple of reliable "testimonials" that this was a legitimate 50mph boat, those came after I bought it so was not just sales propaganda. Seems a stretch to me though from what I have experienced so far. Basic prop calculator shows if I can get 4800 rpm's at 5% that is 50 on the nose, so maybe I did give up on the original High5 too soon.

Going out tomorrow just for a lark hopefully, using my spare 3blade 19p aluminum in place of the 21p and see what happens. The High5 should be here next week.

Just for some background on what is going on inside my head...
The 22' HydroSwift sterndrive boat I had just before this one had a 5.7 275hp with DP-A DuoProp. A legitimate 50mph all day with B7 propset and had grip in every condition, holeshot was great, had minimal bowrise. That is what I am comparing this one to in my brain, hence my disappointments. I did not buy this one for top speed honors, just seems that an 18 footer with advertised 220hp would behave similarly. The DuoProp probably spoiled me without me realizing it!

 

[89retta]

Have a 1.79 SX-M. I've found our current boat is hard to prop for what I'm after. Like I said 2nd to that Apollo 20 pitch the TP 4 blade 19 was great. Mid range acceleration was amazing. I'm with you on hitting that 50mph mark and with a 225 HP Volvo on a 18.5 foot boat think it would be easy. Let me know how you make out with that 3 blade 19

 

[Maclin]

I got the High5 Monday and put it on, waiting for a chance to go out when it is not too hot or windy. Also thinking I may need a proplock for this shiny thing...

 

[Maclin]

The High5 19p is much better. Holeshot is really good, did not blowout in any of the conditions that the 21p was known for., very responsive when maneuvering at speed. Backing up is noticeably less grippy, but is ok for me now that I expect it as normal behavior, not a surprise. I should have hung with the High5 the boat came with a little longer. I sold it last year for about what I paid for this one, it had oxidized and was very dull, this one is polished so I may have saved some money and effort all things considered

Interesting condition this time, I had forgotten to hook the speedo tube at the drive the last time I had it off, and lost my GPS a while back so I had no idea what my speed was. I actually think that was better for me this trip! I could focus on the changes that small increments in trim and throttle made by feelings noises and comfort levels. I keep telling myself that top speed is not important to me, so Karma & Serendipity ganged up on me and give me the chance to see if that is true or not.

When and If I get the top speed tuning bug I will acquire an Enertia 19p and start a new thread with a same-same comparo.

Happy Boating y'all!

 

[SkiGuy1980]

Maclin, glad you got 'er worked out.

Not wanting to latch onto your thread, but what is the ratio that you are referring to? Is there a calculation I need to do before switching props?

I just replaced my 3 blade 21P aluminum with a 4 blade 18P SS based on input from someone that had the same model/engine set up. Huge difference in performance (bow drop went from 8 seconds to less than 4, less likely to blow out, and no blow out due to mild side waves). I gave up about 3 mph... but still hitting 52. I'm hitting about 4900 at WOT (range is 4800-5200 on the 350Mag).