Repitching propeller

[Andy Rogers]

Hi.

In the diesel survey I commissioned as part of the buying process the mechanic noted that the propeller seem overwheeled. The max RPM achievable under load was 2100 RPM on the Universal 1984 M-40. I have found that I typically cruise around 1500-1600 RPM.

The mechanic suggested getting the prop repitched to bring the engine up to normal cruising RPM (2000-2500) to avoid carbon buildup in the engine and to be able to achieve max horsepower when it's needed.

Any suggestions, warnings, or thoughts on the repitching process. I'm about to ship my prop off for a quote and I'm guessing I'll be hit up for around $200-250.

Andy

 

[jwolfgra]

I replaced my prop when I repowered some years ago. First pass we weren't tall enough, I was able to over rev. The prop shop added an inch and everything was a ok. If memory serves, they indicated 2 inches was about the max they could change in on my prop. 200 hundred sounds high to me, is this a fixed pitch two blade, or is it a folder?

 

[Andy Rogers]

The prop is 16RH15 two blade fixed. When I first spoke to them (Machine Works at Essex, New London CT) the person mentioned 2 inches as probably what it needs to get to the appropriate cruising RPM.

I've asked for a quote first and then I'll go from there. I'll report back what they offer to do it for but I'm also interested to know what others have paid in the past.

Machine Works at Essex came highly recommended.

Andy

 

[jwolfgra]

I'm on the west coast so pricing may be different. In my situation, either the prop shop or my engine installer picked up the cost of the repitch, they missized it going in. If memory serves, I got the prop a 12/12 Martec from Killian Prop's in Alameda CA. They repitched to 12/14 for me. The prop itself was just under 300. I thought they mentioned 75-100 for a repitch if I'd been paying. Hope this helps.

 

[Andy Rogers]

I just finished emailing a bunch of prop shops to get an idea of prices. So for, one reply and the person suggested that I need about 10 or 12 inches of pitch so I wouldn't be able to get my 16x15 prop down to that.

Any E-38 owners out there know the diameter and pitch of their fixed two blade props?

 

[u079721]

If memory serves (and I'm out of the country right now so I can't look it up) my '89 E-38 came with a 16" diameter by 13" pitch two bladed prop. The PO of my boat had the prop replaced with a three blade 16" diameter Max Prop, which the yard (in its infinite wisdom) went ahead and pitched at 13"! So my boat was WAY overpropped (is that a word?) when I got her, with max rpm of 2100, down from the 2900 the book says. It two me two or three tries at repitching the Max (which is easy, but does involved having the boat on the hard) to get the pitch down to where the max rpm is again 2900. I think the setting is now 16" x 10.5" for the three blades.

You didn't say how many blades you have, but I wouldn't be at all surprised if a PO of your boat did the same thing mine did, and went from 2 blade 16 x 13 to 3 blade 16 x 13. In any case I would suggest at least a 2" change in pitch, since like me you have a long way to go to get back up to 2900 rpm

 

[u079721]

Woops - Andy I missed where you mentioned in your follow up that you know the current prop is 16" by 15". (I read the posts too quickly.) Given that mine came with 16"' by 13" two blade, I would sure recommend that as a good target for re-pitching.

OR, you could use this an excuse to buy a re-pitchable Max or Auto prop? What the hell, they're only about two grand!

 

[Andy Rogers]

So my quotes came in between $75 and $150 to repitch two inches. This should bring me into the bottom end of the cruising range for the 5432 (M-40) so I've decided to go ahead and have it done by Machine Works at Essex in New London CT.

As for the Max Prop, I've just blown my G's for this spring on a new Harken roller furler.

Thanks to everyone for their advice and help. Very informative, as usual.

Andy

 

[tdtrimmer]

Steve,
I also have an Ericson 38 (1981) with a Universal 5432 (same as the M40) on Lake St. Clair. I currently have a Michigan Wheel 16X13 two blade and have been evaluating 3 blade feathering. I have decided on the Maxprop 3 blade 16. I would appreciate knowing what improvements in speed, vibration, engine performance, boat speed, etc you have achieved by going to the Maxprop. I was going to pitch it initially at 12 but based on your comments, I'll go with 10.5. Thanks, Tom S/V Mistress

 

[u079721]

Wish I could be of more help, but since the boat came with the Max I can't really speak to the changes achieved in moving from a fixed 2 blade to a feathering 3 blade, such as how much better it might or might not have been under sail with the new prop.

I can tell you that the Max is amazing in reverse. A friend with a fixed 2 blade prop is used to using full throttle in reverse to stop his boat, and he was at the helm of our boat once coming into the slip. He went full reverse, and we started backing out of the slip before we knew what was happening.

Nice as the Max is, if I were in the market for a prop today I might be more inclined to go with an Auto Prop. Some friends with a Tartan 40 bought one, and have been very impressed. Supposedly you never have to mess with the pitch, and the effective pitch even changes with rmp. It does, however, have rather more drag under sail, so there ain't no free lunch.

 

[u079721]

OK, I'm back from my business trip to Germany now and I was able to look up the data on my Max Prop. My Ericson 38 originally came with a two blade 16"d by 13"p prop, but the PO replaced that with a three bladed 16" diameter Max, which his yard set to 13.4" pitch - way too much. The manual for my engine suggests the max rpm should be about 2800, but when I got the boat the max rpm was only 2100!

So here is my empirical data for pitch vs rpm for the 3 bladed Max prop on a 1989 Ericson 38:

13.4" pitch = 2100 rpm max
12.2" pitch = 2300 rpm max
11.0" pitch = 2550 rpm max
9.8" pitch = 2850 rpm max

So my recollection of 10.5" pitch above was just a bit off. I'm pretty satisfied with this set up now. If anyone has a Max with this boat, the current settings to get this pitch are X = E and Y = H.

 

[tdtrimmer]

Your empirical data is very helpful. I assume the increments are 9.8 , 11,12.2 with no adjustment in between. Did you settle on 9.8 or 11.0 for your prop pitch? My Universal also has a 2800 max rpm.

I agree, the Autoprop appears to have advantages. The one negative is that if you are in a long distance race and need to start your engine to recharge batteries and thus must keep the engine in neutral, the Autoprop will spin and cause considerable drag; or so I'm told. I also looked at the 3 blade Gori folding prop; a very interesting design. I couldn't find anyone who had one however.

Tom

 

[u079721]

Yes, those weird values for the pitch are fixed, with no adjustment available between the values. And I did finally settle on the 9.8" pitch.

 

[Brisdon]

It cost me about a hundred last time I pitched my prop, but I guessed wrong the first time and had to down pitch it again. Two hundred seems a little high, but everything in your area seems a little high to me. I only know west coast prices. I'm thinking that 16-13 sounds like a good place to be focusing.

 

[Andy Rogers]

So I ended up sending out my prop for repitching my Machine Works at Essex. I haven't received the bill yet but it's going to be between 120 and 140 for repitching, reconditioning, balancing and cleaning. The end result will be a two blade 16x13 which should get me closer to the bottom end of the 2000-2500 RPM cruising range of the 5432 (M-40).

And then next year maybe I'll drop some $$$ on a MaxProp.

Thanks to everyone who provided valuable input.

Andy

 

[juneausailin]

16RH13 two blade to a 15RH12 three blade folder

Hi all, have bought an E38 this week in S.D. area... it came with the 16RH13 fixed two blade. Am thinking of replacing with a Gori 15RH12. It has the 32 horse Universal... The 32 should be able to handle the extra blade given the smaller diameter and lower pitch I would think... opinions?

-david

 

[EGregerson]

prop

Is this the prop gori suggests for your boat (based on its specs?) on their web site? the size seems a little small.

 

[u079721]

On our E38 the PO switched from the stock two blade 16 x 13 to a three blade 16 x 13 Max, which of course was way too much. We finally settled on about 16 x 10 three blade for good performance.

Assuming you too are going to a three blade, I would get a copy of Dave Gerr's Propeller Handbook and run the math to see if 16 x 13 two blade equals 15 x12 three blade.

 

[juneausailin]

Prop Size

Well, I have a couple of goals. I want to reduce the distance between the strut and the prop. So in order to maintain a distance between 12-15% of the prop diameter from the hull I was thinking I would:

1. cut an inch or so off the shaft on the coupling side (coupling has to be replaced anyhow).
2. Drop the diameter of the prop down to 15" from the stock 16" two blade fixed so as to accommodate the smaller distance from the strut to the prop while maintaining enough space betwen the prop and the hull.
3. Thinking the three blade would accommodate for the smaller prop diameter, and in going to a folding prop, help add extra juice in reverse.

Dave Gerr's Propeller Handbook sounds interesting.. will look it up.. thanks for the tip and feedback all..
-david

 

[Greg Ross]

Diameter and pitch determination

If I am understanding correctly, the Gori folding prop has no means of adjusting pitch. Getting the recommendation from Gori - AB Marine as to equivalency to the existing 16 - 3 three blade has to be the way to go.
Would also suggest if she`s out of the water some effort at templating the folded vs swung positions of the blades considering your shortened shaft would be very worthwhile.
Can`t recall which feathering prop I was looking at some time ago but once I`d worked up a representation of the length of the hub vs the aft position of the blades it looked like too much overhang to swing in the space under my hull. Ended up instead with a Max Prop.