Prop advice stainless moving to lower pitch alum and possibly a hydrofoil add

[lilharryjr]

I've read much and spoken w many on this but get as many differing answers. I have just launched our "new to us boat" a 96 celebrity w/ 4.3 l mercruiser 190hp. Right now it has a 21 pitch stainless Mirage and is sluggish out of the hole but a demon at top end...Trimmed out full bore it runs at about 4800, trimed down at about 45-4600. We like to cruise and look around a bit so slow speed planing would be a plus, but we also like to ski/ tube and wakeboard, I am also a bigger person that could use the umph to get up. I was thinking about going to a 4 blade aluminum (we have some shallow areas in our lake)19 pitch...and possibly adding a foil. What's the consensus out there...and how much should I be able to get for the used stainless in good condition?

 

[495v]

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Howdy lilharryjr, I may have some interest in your prop. I have a 5.7l mercruiser and I am currently running a mirage ss 19 pitch. I have great holeshot but sometimes run short on rpm's with a heavy load. I was thinking of going to a bravo1 ss prop, 4 blade with a 20 or 21" pitch. I, personnaly, would stay away from the aluminum props. Do a search on props and you will find some good articles and debates.

 

[lilharryjr]

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Thanks 495v...I'm tossed up on the ss vs alum issue. If it were not for the shallow area where I dock the boat and some other areas of the lake it probably would be an easy decision to go with a lower pitch 4-blade ss. It seems we have less chance of signifigant damage with an aluminum. I have an offer of $300 for the 3-blade 21 Mirage, if you are interested let me know...the Bravo1 is nice though...

 

[Bondo]

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

LILHARRYJR, if your running 4500 to 4800 now,dropping pitch will put you WAY over the rev. limits of that motor, you need a prop style that'll slip a bit more out of the hole, NOT less pitch....try a 21' alu. prop, it'll flex more,+ maybe give you the low-end you need.. the foil will help to keep you on plane at slower speeds...$300. is a fair price for your used prop....495V if you can't pull top rpms now, switching to a higher pitch will LOWER your rpms...you need to go the other way.....

 

[hondon]

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

I can't remember if the Mirage is a ventilated prop or not but if it is not you might consider having it made one at the prop shop .This could give you everything you are looking for with your current prop.Look for three holes near the leading edge of the blades in the prop body.These holes allow exhaust to escape during hole shot causing some slip and allowing your engine to achieve higher hole shot rpm.Vented props can make a big difference.

 

[lilharryjr]

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

I went down to a local shop that carried Solas props and the proprietor was adamant that a 17" 4-blade aluminum was the way to go. He insisted that the boat should have had a 19 3-blade to begin with (I'm not sure on this)hence go down two. So, he says try it and if it is not good bring it back for the 19. I get it on yesterday and the thing does do a much better job of getting the boat on plane and keeping it there. Also, the boat does hold the water much better, less porpoising. But at WOT it is running 5k maybe just a bit more. And not that I really need the top end but I seem to have lost 5mph, I'm not exactly sure on the mph as I need to fool with the speedo and get it working.<br /> I'm wondering if this is not good and am thinking of going back to swap out for the 19 I had wanted in the first place...

 

[lilharryjr]

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

This prop thing is going to keep me up nights I swear. I spoke with Mercury again today and it's tough to get a straight answer. I like the idea of the four blade aluminum, but getting the pitch right would be nice. My main concerns are these:<br />1.) WOT RPM's @ 5k, this seems high, is this something that will cause problems?<br />2.) Have I sacrificed too much top end by going to a 17" pitch.<br />3.) Will a 19" pitch give me about the same hole shot as well as increase top end and keep revs down @WOT?<br />4.) What effect will more persons in the boat have? Often we have 4-5 adults for cruising and skiing...<br />Thanks again to "hondo" "bond-o" and "495v" for previous responses...

 

[sho305]

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

It is a tradeoff: small prop = good holeshot and skiing, bigger prop = slow holeshot and top speed. <br /><br />I have used clevor type props that rev for holeshot but they are a pain. I found that 4 blades reved less at low rpm and are slower on top end, but that could be boat specific. They are more stable in handling and blow out and useful if your drive(s) are mounted high. I found a Mirage best for all around use. I sharpened the leading edge for 100-200 more rpm and 2 mph, then trimmed up quick just as it came on plane for some cavitation to rev it up. It would grab and plant you in the seat. I used engine mods for more power to pull it but was using a BB chevy mostly(some @6500-6800rpm, 500+ hp). Also ran 305 & 350s. Mercruser normally says rpm range on spark arrestor on carb. The top rpm w/empty boat & trimmed out usualy best if stock, higher if mods. I used SS props only as they were fastest and would hold a good edge. Never pulled skiers at 80mph on Lake Michigan you know, but I think it would have.<br /><br />A hydrofoil might help you get out of the hole better too if your cavitaion plate is out of the water on plane. IMHO, would not use if above not true, otherwise they work good.<br /><br />Extra weight in the boat will just slow the mph/rpm a little per 100lb. You mostly set it up for what you do the most, or top speed if it will still pull a skier or whatever you can get along with(my choice). Over rev is not a good idea with a stock motor. A little normaly does not hurt, but you are just taking life off the motor. Typically stock motors make LESS power above the spec. rpm anyway so it is pointless unless you get a better exhaust, etc, and then improve the valvetrain. That is why it can be slower at a higher rpm with a smaller prop, it is past the powerband. Great for skiing and burning fuel, not top speed. Also can cause valvefloat, a ticking time bomb. Every motor is different though, and some pull at higher rpm, most GM do not if stock. Factory leaves room for error, so stay close to specs and it is ok. I would try/borrow a 19 and see if it will do the job. Best to have the biggest prop that will work, otherwise get two and change out for your use; lots of people do.

 

[bertherr]

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

How about one prop that gives you the best of both worlds, good pull from a stop and protection from too many RPM's? I have a QuickSiler Power2 stainless prop. I used it on a 3.0L Mercruiser in a 17' SeaRay. It starts out @ 17" pitch and then shifts to 21" pitch. It makes your boat work like you have an automatic transmission. It felt like I added 4 more cylinders to my boat when I put on this prop. I sold my boat without the prop and now have a new boat with a Yamaha HPDI. I want to sell the prop. I have scanned the information I have from QuickSilver if you want copies. Email me and I will send it. bert.herr@perkinelmer.com.

 

[lilharryjr]

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Well, looks like trial and error will prevail. I called the guy who sold me the prop and he says"he told me" that 17" was too low LOL? Anyway, he's a nice ol local guy and he has no problem swapping out for 19 4-blade. After reading the posts on "Do hydrofoils work" I think I may also try this, or get the file out...could be a mute subject if I continue to have trim pump probs (please do not confuse me with that golfer69kyonhisass scum). Thanks all for your replys...Great site here!

 

[SeaDawg]

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

lilharryjr, you really did hit the nail on the head with some "trial and error" testing. The best thing that anyone can have is someone that will let them swap props if they guess wrong.<br /><br />Every boat is loaded differently, the water conditions are different, etc. and on and on.<br /><br />You can theoritically calculate what you think you need, and it can still be different when you hit the water.<br /><br />Bottom line rule of thumbs are: a hydrofoil will usually help you get on plane better, sometimes hurt top speed slightly.<br /><br />A higher pitch prop will generally slow your hole shot (but not always)<br /><br />A less pitch prop will generally hurt your top speed (again, not always).<br /><br />Soooooo trial and error is always the the absolute right answer, IF you can swap props at no cost, except your time.

 

[Clay]

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

Re: Prop advice stainless moving to lower pitch alum and possibly a hydrofoil ad

If you can, try a 21 high five It will plane quicker and stay on plane at lower rpms. you may also gain rpms at wot. I would stay away from foils on stern drives.