What's a good Prop for my 4.3L 220hp 18' open bow?

I have a Tahoe Q5 (18' open bow runabout) with a 220hp 4.3L MPI Mercruiser. I have two teenagers that wakeboard and water ski. My boat has a good top end speed but has trouble getting out of the hole. I had an aluminum 3 blade 21 pitch prop and went to a steel 3 blade 19 pitch. I saw no difference at all. A friend told me that it's because I went from Aluminum to steel and that due to the fact that aluminum flexes and steel doesn't I wouldn't see a difference. So I figure I should try a 17 pitch steel, or should I get a 19 pitch aluminum? I really like the looks of the stainless and I figure it will last longer, assuming I don't hit anything.

Thoughts?

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

Ayuh,... What kinda Rpms are ya turnin' at Wot,..??

Normal load...

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

Between 4500 and 5000.

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

If the aluminum three blade 19 is stock, then a four blade 17 would give you a better hole shot and keep your RPM's where they were, for the most part, based on my experience.

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

Between 4500 and 5000 is a pretty broad range especially since each inch of pitch change with the same manufacturer and series of props changes RPM by 200 up or down. Lets be a little more specific.

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

gwershing said:

I have a Tahoe Q5 (18' open bow runabout) with a 220hp 4.3L MPI Mercruiser. I have two teenagers that wakeboard and water ski. My boat has a good top end speed but has trouble getting out of the hole. I had an aluminum 3 blade 21 pitch prop and went to a steel 3 blade 19 pitch. I saw no difference at all. A friend told me that it's because I went from Aluminum to steel and that due to the fact that aluminum flexes and steel doesn't I wouldn't see a difference. So I figure I should try a 17 pitch steel, or should I get a 19 pitch aluminum? I really like the looks of the stainless and I figure it will last longer, assuming I don't hit anything.

Thoughts?

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The fact that there is no difference to you probably means you are under propped from the start. Post your gear ratio it is on the outside of the drive on a merc it should be on the very back of the leg aka 1.6...1.89...2.0.. With a 1.6 drive that boat should need a 21 or 22p agressive 3 blade ss

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

I need to check the actual RPMs next time I go out. Sorry that range is the best I could do from memory.

The Ratio reads: 1.62R. Wouldn't pitching it up make it lag more?

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

Put on the 21 and get actaull readings. use gps and see if your tach is accurate if you can. I know its only a boat but a good ss prop runs 300 and above take some time if you can. Two things come to mind a trim tabs and a 4 blade ss....tabs get you out of the hole and the 4 blade makes the boat respond from plane to high midrange. You may lose 1-3 mph with a well picked ss...probably gain speed over the 21 alum you have now

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

Another thought is to work with a prop supplier who allows trades- you keep same brand/model of prop, but can swap up and down in pitch for a reasonable time after purchase with no penalty, assuming prop is in good condition when returned, etc.......
Sometimes you just have to run and experiment.
To share my personal experience, I have the same motor you do and my boat is similar. I was running a 21P Alum. 3 blade, and swapped it for a 19P Stainless 4 blade. Worked for me- better overall performance, pops up on plane quicker, and stays on plane at a lower speed. That's my experience. Yours may differ, hence the niceness of being able to swap around till you find the right prop.

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

Tail_Gunner said:

Put on the 21 and get actaull readings. use gps and see if your tach is accurate if you can. I know its only a boat but a good ss prop runs 300 and above take some time if you can. Two things come to mind a trim tabs and a 4 blade ss....tabs get you out of the hole and the 4 blade makes the boat respond from plane to high midrange. You may lose 1-3 mph with a well picked ss...probably gain speed over the 21 alum you have now

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I don't understand how to use a GPS to check the tach? you mean check the speedometer? Also, when you say trim tabs, are you talking about a hydrofoil for the out drive or actual transom mounted tabs?

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

gwershing said:

I don't understand how to use a GPS to check the tach? you mean check the speedometer? Also, when you say trim tabs, are you talking about a hydrofoil for the out drive or actual transom mounted tabs?

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These are trim tabs they lift the boat out of the water aka a better hole shot everytime

http://www.iboats.com/SX-Smart-Tabs...3225876--**********.002001174--view_id.352488





As to gps it gives a very accurate measurement of speed and give people a ideal of just how far one can push prop size...Talk to some kids..gps is avaible on most cell phones

As to your tach it again is a way to again push the limits of performance...200 rpm can make a difference but in this case never mind

Hydrofoils were great in the 70's tabs have replaced them

That 19 is to small.. Id pick a Stilletto baypro 2 in a 20 pitch and the boat would be ready for anything including a full passenger load....Or a Solas 21 pitch hr titian in a 4 blade ...put those tabs on and have fun

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

I'm hoping I phrased my question properly. My problem is that when I try to pull a skier out of the water I can't seem to accelerate quickly enough to pop them up. I can pull my 14 year old up okay, but I feel like if i tried to pull and adult it would be tough. I need quicker acceleration.

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

Then the trim tabs would be all you need

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

Get a Merc High Five prop and be done with it. I had the same issues before I put one on mine. Boat leaps out of the water now pulling a skier or boarder. I put on a 19 pitch unit, similar boat to yours. They're a bit pricey but worth it.

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

fossill said:

Get a Merc High Five prop and be done with it. I had the same issues before I put one on mine. Boat leaps out of the water now pulling a skier or boarder. I put on a 19 pitch unit, similar boat to yours. They're a bit pricey but worth it.

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Not a good solution by any means. Tabs will lift the hull out at a far more reasonable price.

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

I want to clarify for original poster regarding the recommendation of trim tabs. Do NOT take the cheap route and purchase Smart Tabs for this boat. I am an avid wakeboarder who purchased Smart Tabs for my runabout several years ago, with all the same hoopla and promises that are still given for the product, I can attest that they do everything they are advertised to do. They also do something that is NOT advertised...they completely wash out and destroy a good clean wakeboarding wake. After much adjusting and talking to the manufacturer who was very helpful in supporting their product, I gave up and removed the Smart Tabs and went to power trim tabs...and after I learned to use them, I got my wake back. The Smart Tabs were good for skiing. They were NOT good for wakeboarding tricks.

Wakeboarders NEED their hull to sink into the water to create a nice clean wake for jumping. Therefore only adjustable power trim tabs can provide this solution (as Tail Gunner is suggesting). Run tabs down for takeoff to help holeshot accelleration, and then lift them up flat (or even higher than flat) as soon as the boat planes to allow the hull to sink and create a nice clean wake for jumping.

I also agree that a 4 or 5 blade prop will help with holeshot more than you may realize over your current 3 blade. High 5's are expensive, IMO too expensive. But a good quality brand new stinless 4 blade can be had for $300 to $350, and an aluminum 4 blade for much less. Both alternatives cost much less than a set of power trim tabs, and are substantially easier to install. I feel it's worthy of trying. But what pitch should you buy? We have no idea....

I'll echo Silvertip that "between 4500 and 5000" at top speed is WAAAY too big of a range to make a specific recommendtion. We need an exact number. I'm not sure how Tail Gunner figured out that 19 is too small without knowing your RPM? Probably based on boat weight/size, etc...and I agree that makes sense. But if you were still at at 4500 with that 19 SS you tried, then I suspect that exactly is why your holeshot was still pretty poor, and in that case a 21 or 22 would not make any sense at all. But if you were spinning 5000 with that 19?, then your holeshot should have been maximized and you certainly wouldn't want to go any lower in pitch or you'd over-rev. There is a HUGE difference in holeshot between these two RPM numbers.

To summarize, everyone is making educated guesses based on questionable data. You need to provide more accurate RPM information in order for anyone here to provide more specific recommendation of what you should do...but as a generic answer, yes trim tabs will always improve holeshot. And yes 4 and 5 blade props will ALMOST always improve holeshot...but that depends fully on your exact current 3 blade RPM, and projected your 4 blade rpm.

Re: What's a good Prop for my 4.3L 220hp 18' open bow?

If you shop around a High Five can be had for around $400 which isn't too bad compared to other 4 blade stainless units out there. Lots of people use them without complaint. I too looked at trim tabs but after looking at several boats with them installed I figured it ruined the look of the boat, plus I never wanted to go about drilling all kinds of holes in my brand new boat. With the prop it's "plug and play" without having another set of toggle switches to operate as the boat speed up. To each his own, I prefer the prop route. There are thousands of newer Tahoe Q5's out there already running 5 blade props, so all you have to do is go to your dealer and find out what prop pitch works for that particular boat.