Underpowered, which propeller to install?

[inquestof]

I have a 326 Hunter sailboat. It is sluggish at best while motoring. I have read tons of info about folding and feathering props... almost to much info. I have read the pro's on con's on them all... however cannot come up with anything that convinces me to make that choice. Does anybody have experience with the Gori folding props? Maxi-props? EWOL props? My goal is to reduce the prop-walk in reverse and get more forward bit from the propeller. All of them reduce drag under sail, which is not that big of an issue being my boat sails amazing in all conditions. As info... Not interested in the Kiwi prop...

[UNCIVILIZED]

Max Prop's can be pitch adjusted in the water while in place, on the shaft, sans disassembly. Great thrust ahead & astern. All are traits which most folders lack. But it's not as if there's a dearth of prop reviews & comparisons done by Practical Sailor & similar. Ditto comparisons of them here on CF. And probably about 30 sec after I post this the EWOL prop vendor will chime in

Edit: It's worth talking to a prop shop/repowering specialist in order to first best diagnose what the problem is. Otherwise you could be spending lots of coin on at best, semi-educated guesses as to what's wrong, & why.
Including doing simpe things like temp. analysis in a few places on the engine, & exhaust. Oil analysis, ditto transmission fluid. Etc.

Kinda' like when someone has back trouble, & you notice that their poor posture begins at their feet. Without fixing that first, no wonder drug, or surgery will fix the problem ultimately if they have the muscle tone of overcooked noodles down there, or anywhere from their feet to their ears.

[Cheechako]

I've had many Max Props and love them. But they prop walk as well as any. I like prop walk, it can be used to advantage quite well on a long keel bot etc. Seems to me the less a prop walks... the poorer it's working....... true? I like the Max for it's reverse thrust. I found no noticeable difference in forward fuel efficiency vs a 3 blade fixed.

[JPS27]

I would just add to the above post that I was way underpowered due to replacing an engine A-4 to diesel, but waited on prop change due to lack o' funds. I found that practically all I did in reverse was prop walk. and forward was pathetic. I took advice like given above. After listening to know it alls in my marina I decided to listen to a prop shop expert. I went with 3 bladed michigan prop because I'm concerned with control not racing. I now don't worry as much about unwanted prop walk. usually get the boat moving back and then put into neutral and rudder starts to bite. And foward hit hull speed with room to spare. Frankly maybe notice .25 knot drop in speed. Just my two cents. Talk props is like talking religion or politics I have found!

[Cheechako]

Re-reading the original post... if you are "underpowered".... meaning too small an engine, not sure the answer, probably the biggest diameter prop with least pitch. if that is what you meant.

[UNCIVILIZED]

Yes, as stated above, the difference clarification from your initial statement does certainly play a role. That said, with something like a Max Prop, you won't need to be in reverse for nearly as much time as you would with a standard prop, as it's efficacy in reverse is so much higher. Thus the actual amount your boat walks due to the prop will be less, or less so long as you don't stay in reverse for intermediate to extended periods.

Putting a Max Prop into reverse is kind of like putting Corvette sized disc brakes on a bicycle. You stop NOW if/when you apply any amount of RPM's astern. Ditto on using it to propel the boat astern. And this applies to most reversable pitch props. The EWOL for example, or the brand that Ann & Jim Cate have. Can't recall what it is at the moment, but it works!

One other tip, fiscally, is if you find the right sized used Max Prop for your boat, you can have it factory reconditioned. The blades, the gearing, pretty much everything. And a few folks here on CF have had good things to say about their experiences with same. Plus the pics that they posted of the prop before & after it's tune-up were amazing.

[inquestof]

The engine is a 18 hp diesel and according to Hunter and a few other shops... the boat has the power but the power / prop combination leaves you wanting. From what my mechanic says ... a bigger motor will give me bigger problems. Also I have talked to other Hunter boat owners and they all say they are under powered. Only most leave well enough alone... I read one article where a Kiwi prop was the fix... however I cannot put a fiber prop blade under my boat and feel good about it.. and they recommend buying extra blades... I could not live with having to fix out in the middle of the ocean... thank you all for the responses...

[IslandHopper]

Assuming the boat is still in it's original form with original engine (or repowered with same) get in touch with the boat manufacturer, they can tell you what the correct prop should be for optimum performance (is it still the original prop?)

As for trying to remove the prop walk in reverse question? propellers are almost always optimised for forward propulsion (fixed or feathering) what you get in reverse and the resultant prop walk is what you have to live with (and learn to use to your advantage) trying to reduce the prop walk in reverse will adversely affect the forward performance.

As UNCIVILIZED suggested, get in touch with a specialist and go through the process of elimination first, far cheaper and less stressful than trying to nut it out yourself......

Edit: I have just gone through a similar process, I've just repowered from a 40hp up to a new 75hp 4JH4-TE, Yanmar would not sign off on the warranty until the engine was running within the accepted rev range at WOT. It took 2 pitch adjustments (fixed 3 blade) to get it right, the initial on the hard stand and another after a sea trial, and as I'm a full keeler, I love my prop walk....


2nd Edit: I see you have already mentioned getting in touch with Hunter while I was still typing, way to go.

[IslandHopper]

I wouldn't write off the Kiwi Prop just yet, one thing the Kiwi's know (besides sheep) is boats, might be worth spending a bit more time looking into....

[inquestof]

I was sold on the Kiwi prop at first... but then did more research and found a few folks that had issues with them breaking. Kiwi recommends buying extra blades... Over the years I have hit logs and other sunken debris and do not want the prop to break off while away from port. My boat is heavy... reason for the sluggishness but is a fin keel and the rudder is huge... and sometimes the prop walk does help... but more often not. Thank you for the reply...

[inquestof]

Also as info... I have talked to all of the manufactures about the proper propeller for my boat... and they all have the solution... funny how that works... the Gori manufacture almost had me sold... after reading the study from the Practical Sailor magazine... I started questioning the whole idea of changing the prop.

[a64pilot]

OK as far as producing thrust, nothing or almost nothing can match a good cheap fixed blade prop. Most feathering props like a maxprop, the blades have no aerodynamic profile, they are flat plates, and a flat plate will never produce as much thrust as a properly shaped prop blade.
Many people will vehemently disagree, but it is true, prop blades are shaped they way they are, because that shape produces the most thrust.
Another thing that a proper blade has that feathering props do not is twist, that is the angle of attack at the hub is higher than at the tip. This is also necessary to produce max thrust.

So if you are after more power and thrust, nothing will equal a proper fixed blade prop, and it will be hugely cheaper too. It will have more drag sailing though, there is rarely a free lunch.
I left an Autoprop out as it may come close to a fixed pitch prop in producing thrust, but they are stupidly expensive and almost certainly not what you need, waste of money.
All this is in my opinion of course.

[Jim Cate]

The EWOL for example, or the brand that Ann & Jim Cate have. Can't recall what it is at the moment, but it works!

The prop on this boat is a Flex-O-Fold three blade, and this is not a feathering prop, but the best of the folding prop offerings. On our previous boat we had an AutoStream feathering prop, made here in Oz, and IMO, a better bit of kit than the Max Prop, and at a considerably smaller price (when we bought it in ~ 1998). Dunno about now.

When considering feathering props, one needs to factor in their lower efficiency than other prop types, due to the flat, non-twisted blade shape and in the smaller diameters, the relatively large hub diameter which limits blade size. There have been numerous threads on this subject here on CF, and if one looks at actual data instead of personal opinions, the F-O-F actually outperforms the Max prop except for static thrust in reverse. Whether this, or any prop will help the OP's situation is beyond my pay grade, but if I was worried about lack of power I'd not be willing to take the efficiency loss associated with a feathering prop of any manufacture.

Jim

[a64pilot]

The reason a good fixed pitch prop is so poor in reverse is two fold. Mostly it is because the leading and trailing edges swap, that is the prop is being turned backwards so that it is very inefficient, a feathering prop, the flat plates just change pitch and it is as efficient in fwd as reverse.
The other reason is that usually a transmission has different gear ratios for fwd and reverse.

The odd ball is the Autoprop, it's blades actually spin completely around so that the leading edge is still the leading edge, even though the shaft is turning backwards. I believe it was actually designed to be the most powerful prop possible in reverse as it was designed to get a WWII landing craft off of the beach. I guess they later hit on it being a sailboat prop.
However putting an Autoprop on your boat would be as foolish as putting carbon fiber laminate racing sails on mine, lipstick on a pig

[Pete7]

Originally Posted by inquestof

I was sold on the Kiwi prop at first... but then did more research and found a few folks that had issues with them breaking. Kiwi recommends buying extra blades... Over the years I have hit logs and other sunken debris and do not want the prop to break off while away from port. My boat is heavy... reason for the sluggishness but is a fin keel and the rudder is huge... and sometimes the prop walk does help... but more often not. Thank you for the reply...

I think I would rather have the prop blades break than the gearbox from hitting something solid. I tended to run ali props on the dive boat rather than stainless steel for this reason.

Pete