E28 prop size

[mattingamells]

Just bought an E28 with M12 diesel. Has 12x7 two blade propellor, but has trouble exceeding 5 knots in flat water. The owners manual says a 12x10 is the standard propellor. If you have a M12 with this propellor are you satisfied with the performance? The standard panel does not have a tach so Im not sure when/if I'm at max rpm. Thanks for any input.

 

[Dave G.]

A 7" pitch sounds low for a 2 blade prop IMHO. If that prop hasn't been re-pitched before you could have a prop shop re-pitch it to 9" as I don't think they can go more than 2". That may get you another knot but I would contact a prop shop or 2 and get a quote for your boat and they should be able to spec the right prop for your engine and trans. You may need to supply the engine and boat/hull specs , but most reputable shops should have that info on hand. What year model is your boat(28+ or 28-2) ? You can put all your boat info into the signature line as that helps others give more precise answers. I'm guessing with an M12 it's a 28

 

[mattingamells]

A 7" pitch sounds low for a 2 blade prop IMHO. If that prop hasn't been re-pitched before you could have a prop shop re-pitch it to 9" as I don't think they can go more than 2". That may get you another knot but I would contact a prop shop or 2 and get a quote for your boat and they should be able to spec the right prop for your engine and trans. You may need to supply the engine and boat/hull specs , but most reputable shops should have that info on hand. What year model is your boat(28+ or 28-2) ? You can put all your boat info into the signature line as that helps others give more precise answers. I'm guessing with an M12 it's a 28

Thanks Dave, its a 1986 E28. I'm pretty sure a 12x10 prop is in the ballpark, but wanted input from other M12 owners before I spend $500 and wait 3-4 months (3/4" shafts are unusual and prop must be ordered).

 

[Alan Gomes]

Have you considered going with a Campbell Sailer prop, sold by West by North? It's a great, low-drag fixed 3-blade prop. Their tech support is also fantastic and I'm sure they could advise you on just the pitch you need for your engine.

 

[Second Star]

For a 28 with a LWL of about 24 ft the best hull speed is 6.5 kts. (1.34 X sqrt of LWL) This of course just deals with the hull shape. further limiting factors are the HP of the engine, the prop and condition of the hull surface. The M12 is a bit small in HP to get max hull speed IMHO and the 2 blade prop may not maximize the available HP. My 28+ when clean with a M18 (15 HP) and 3 fixed blade 12X12 makes best speed of 6 kts over a measured mile in 2 directions.

 

[mattingamells]

For a 28 with a LWL of about 24 ft the best hull speed is 6.5 kts. (1.34 X sqrt of LWL) This of course just deals with the hull shape. further limiting factors are the HP of the engine, the prop and condition of the hull surface. The M12 is a bit small in HP to get max hull speed IMHO and the 2 blade prop may not maximize the available HP. My 28+ when clean with a M18 (15 HP) and 3 fixed blade 12X12 makes best speed of 6 kts over a measured mile in 2 directions.

Thanks Dave. Just got a recommendation from West by North for a Campbell Sailor 3 blade of 11 x 5, which seems like a very small pitch. BTW, does the E28+ have the same hull as the E28 such that replacing the M12 with a M18 is not too difficult, if not expensive?

 

[Alan Gomes]

Just got a recommendation from West by North for a Campbell Sailor 3 blade of 11 x 5, which seems like a very small pitch.

The Campbell Sailer is pitched less than a conventional prop.

 

[Second Star]

I've only looked into a few 28s. The 28+ denotes the fractional rig not the hull. The interiors are different but the basic hull shape seems the same. The M18 is an older engine, which I think is out of production but, a used one would likely be available. The effort and expense may not gain you much. A new Beta or such would cost more but deliver a lot more reliability long term. I've never changed out an engine for different, but many in this forum have great experience with it.

 

[Special K]

Our E28 also suffered from low speed from a fixed 2 blade prop. We switched to a Flex-o-fold 2 bladed folding prop. Not only did I see speed of 6 knots under power, but also an increase of sailing speed of .5 to 1 knot. Although the cost is significant, I highly recommend that you consider a Flex-o-fold.