Four and five blade props

[sub2010ss]

I'm interested in a prop that can get my boat on plane fast. Does anyone have any experience with these props, which brands would be good? My I have a bayliner Capri 2050 with a 5.7 repower up from a 5.0. I have a vengeance 21p prop right now that was tapping on the rev limiter at 5200 rpm doing 53 mph with a full load an not at wot yet. Any advice would be great.

 

[achris]

Best way to turn a boat into a propelled rocket is a vented prop, like a High 5 and Laser II... Pull the vent plugs out and HANG ON. That thing will rev instantly to about 3000, then take a nice bite of the water and have you at cruising speed faster than a 747 can accelerate (and that is not a joke!) If you plan towing a skier, WARN THEM! or you'll be putting arms back in sockets! When I had my boat shop I took a Laser II for a spin. Hit the throttle, there was nothing but the engine revving up for the first 0.8seconds, then it was like someone lit the afterburner, that thing just got up took off like we'd been shot out of a cannon. Hardest acceleration I've ever experienced (and I travel all over the world for work, so I know how planes accelerate!).... The closest I have come to feeling that again was a 'car' a friend built. It weighed about 1,000lbs, had a 2l twin cam engine and would do 0-60mph in about 4.2 seconds... Scary as all get out.... And in the boat I had to pull myself up on the steering wheel because it felt like the seat would break if I didn't...

 

[sub2010ss]

Do vented props work without through prop exhaust? My exhaust ports out well above the prop.

 

[steelespike]

We probably need your gear ratio to make a educated guess to get you within rpm range.As it stands now with the 21" prop hole shot should be impressive.
Though I don't know if the Vengeance is a good hole shot prop.Keep in mind an I/O is tail heavy and you added a little more with the 5.7.
It seems I recall that someone said Vented props aren't that effective with a I/O.
I don't think there is a rev limiter your motor was simply at its design limit.
You will need to increase pitch to get your rpm down. Increasing pitch usually slows hole shot.
The gurus will be along to suggest some ideas I'm thinking a 24" pitch if your tach was accurate and you weren't at wot yet.

 

[floater212]

I have a 21' rinker with the 350 mpi, we do a lot of skiing and tubing. before I used a 21" 3 blade and it was ... ok. slow out of the hole, the boat had a spare 21" high five so I put that on what a difference in hole shot, then my kid hit a submerged something... poof no more high five, all bent up, took it in for rebuild and they said, " I don't know who did this but it's been rebuilt 2-3 times and not by someone that knows what they are doing, all the blades didn't match pitch and they were skinnier too". I found ron hill props and got one of those in a 19", it's a full 14 1/4" dia. ( not like the 13 3/8" dia high five) and the pitch is dead on and cost less than the high five, now with a full load ( 10 people) no loss of speed or bite. it will throw you back in your seat! better prop in my opinion.

 

[achris]

...Though I don't know if the Vengeance is a good hole shot prop.Keep in mind an I/O is tail heavy and you added a little more with the 5.7.

I have a couple of Vengeance props and although not as good as a 5 blade (for obvious reasons) is still quite impressive. Even cruising at around 20knots, if I open the throttle hard, I get a kick in the backside...

The weight of a 5.0 and a 5.7 are EXACTLY the same... So he has not added any weight whatsoever.

It seems I recall that someone said Vented props aren't that effective with a I/O.

If that's the case, they must be nothing short of heart-stopping on an outboard. On my 4.3LX a vented 21" Laser II was accelerating far quicker than I even expected, or believe my boat could ever do...

I don't think there is a rev limiter your motor was simply at its design limit.

Need to know what ignition system he has to know if there's a rev limit. One thing he does need to consider, and this may be contibuting to his performance problem (and I've only just realised it :facepalm is he changed from a 5.0 engine block to a 5.7 engine block. Now, the rest of the gear is bolt-off, bolt-on, but the ignition module controls timing advance, and there is quite a difference in the curves between those 2 engines....

You will need to increase pitch to get your rpm down. Increasing pitch usually slows hole shot.
The gurus will be along to suggest some ideas I'm thinking a 24" pitch if your tach was accurate and you weren't at wot yet.

He also needs to get a 'shop-tach' in there. Dash tachos are notoriously inaccurate....

Do vented props work without through prop exhaust? My exhaust ports out well above the prop.

Last drive without thru-prop exhaust was a VERY old Volvo or Chrysler. What drive do you have? (knowing it's likely a Mercruiser since you're running a Vengeance prop... ??????)

And there in lies another issue... Props like Vengeance, Laser, High-5, Mirage, etc, etc are designed to have exhaust gasses running through them. It's part of the 'tuning' of the prop. No exhaust gases means a massive vacuum is created behind the prop, seriously limiting performance.... This may well be the reason your acceleration is so off.... It would be like trying to drag a small parachute behind you.

If your exhaust ports are 'well above the prop' because of thru-hull.... Ditch them, and go back to thru-prop. The performance benefits of thru-hull on a 5.7 engine can't be measured, it's that little.... And you're acceleration will be considerably improved.

Chris.......

 

[sub2010ss]

Well at least my train of thought isn't far off from yours. I did some pretty extensive research on the ignition system on my engine yesterday. I don't know exactly where the limiter is set but it definitely has one. That drug on my mind for over a week when I brought this up before and someone said I didn't have a limiter and that there was another problem. No matter what my load was I was hitting 52-53 with either a fast pop pop or a slow pop pop and not at wot.

My thought was I've read now a few places that stated that more blades hurt top end performance. I don't mind that as 50mph is fast enough for me. But I'd like to be able to go wot without rapping on the limiter with a full load of 3 adults and a boat full of kids.

Gear ratio is a good question. I couldn't find a legible serial number on my drive to save my life. The closest I can read is E444504 but I cant be certain on all of those digits. Its stamped in but not clear at all.

 

[achris]

Can you at least give us a year? Serial numbers are useless if incomplete or inaccurate... But I suspect you have a 1.62:1 as it was a 2bbl 5 litre engine, and that was the 'standard' ratio supplied with those engines. BTW, if that's the case, that will not hurt your acceleration... You'll just have to find a 'taller' prop...

EDIT: Just ran your numbers through my prop calculator and 1.62:1 looks right... HTH

 

[sub2010ss]

That is what I was thinking. The boat is a 1999. The engine was the 5.0, 2 barrel carb, vortec.

 

[SkiDad]

I wonder is a 23p high-five is the way to go - i've seen a few of those on ebay. I don't have personal experience though. I do know larger diameter can help your plane time.

Chris, is that calculator available online for use ? that looks really COOL !

 

[muskyfins]

Somewhere I recall reading that the high five was designed as an outboard prop?

 

[achris]

I wonder is a 23p high-five is the way to go - i've seen a few of those on ebay. I don't have personal experience though. I do know larger diameter can help your plane time.

If you have the torque to carry it through.

Chris, is that calculator available online for use ? that looks really COOL !

No, that's mine... As in, I own the code... I wrote it...

Chris.....

 

[achris]

Somewhere I recall reading that the high five was designed as an outboard prop?

It was designed as a ski prop. But they work very well on stern drives...

 

[sub2010ss]

Thanks for all of the advice. I am definitely looking at the High Five.

 

[floater212]

try Ron Hill, they are a full 14" diameter prop which means more power will go to the water and the wider blades would bite better and about 1/3 cheaper than high five. they also have a great help link, I had a 21" pitch high five and they suggested a 19" and my boat is quicker and faster than the high five even with 10 people in the boat! their claim also states a slip ratio of 6-8% and it feels like it too.

 

[sub2010ss]

Awesome! Thanks for the advice. I'll definitely check them out!

 

[sub2010ss]

So I found a used high five on eBay that I got a pretty good deal on. It's a 23p so I'm hoping it isn't too much. Find out soon and I'll post the results.

 

[sub2010ss]

I got my prop installed today. Crossing my fingers for nice weather on friday so I can get her out and see how she runs.

 

[sub2010ss]

Finally got out on the water today. I went from a 21p Vengeance to a 23p High Five. My top speed seems about the same. I didn't trim it out at all but was tapping right about 5200 rpm at 53 MPH. What I did notice was much quicker plane, and much better low speed control. It feels strange though. At top speed it feels like its trying to lift the back end right out of the water.

 

[smokeonthewater]

You need to always trim up for high speed