E 35 Speed v Propeller

[barrett]

I have an 87 E 35MkIII with a Gori folding 2 blade propeller. Max speed is about 6.2 kts at 2500 rpm on the M-25XP engine. Engine will go to about 2800 rpm but with no additional speed. However, at 2100 rpm speed down to 5 kts, and in any kind of seas or headwinds speed falls in 3.5-4.5 kt range at 2300-2400 rpm.

My questions are: 1) do these speeds strike others as slower than expected, and 2) how much of it is due to the Gori Propeller? Don't know propeller model or pitch (installed by PO), but when hauled boat for survey prior to purchase noticed blades covered with light pitting-wondered if this could explain performance of prop, of if I am just facing the tradeoff of low drag under sail for limited performance under power.

Thanks in advance for any thoughts.

Jeff Barrett

 

[Loren Beach]

If you look at my 11-7 post in this forum you can see what my featherer looks like. Note that these types of prop have no cupping for best efficiency. Perhaps your folder is like this, also. I can say that I get about 6. kt at 2300 rpm and with a clean bottom can get over 6.5 at 2800.
I can maintain about 5.5 kts with maybe 10 kts of headwind and a one ft chop. In bigger stuff I too slow down to 4 kt.
I also have an M25XP.
Depending on how pitted your prop is, this could well lower the efficiency. What with the inherent inefficiencies of folders and feathers, the only solution may be to go with a 3 blade featherer or an AutoProp (bigger $$ involved). More blade area is always good, other things being equal.

Best,

Loren
'88 Olson 34

 

[Duncan]

Maxprop: propeller and performance

on an E34 '90 with a fairly dirty bottom using a 15 inch folding maxprop and the M25XP I get 5 knots at 2100 rpm, 6.2 at 2600 and it slows down with adverse wind and sea. sounds the same.

 

[escapade]

more prop stuff

I'm getting 6.0 kn @ 2200 with my '88 E34 & M25XP. This is a Martec 2 blade folder. The proper pitch & diameter can make a HUGE difference. Went with 1" more diameter & I believe it was 3" more pitch than the standard 2 blade fixed. I will have to look again to get the exact numbers. Big improvement in both forward & reverse thrust plus increased sailing performance! Plus the cost was MUCH less than a 3 blade feathering. Used Martec's recomendations (we are in fresh water). Talk to the Gori people & describe your concerns. You might just need the proper blades to maxamize performance. Lot's cheaper than all new.
Have fun & sail fast
Bud E34 "Escapade"