Overpitched Maxprop

[rotorhead]

Last time we went sailing, I could not get the engine (Yanmar 3JH2E) past 1,800 rpm, so i suspect the Maxprop is overpitched. Based on the engine's user manual, maximum HP should be around 3,400-3,600 rpm.

Does anybody knows if adjusting the pitch on one of these props can be done underwater (SCUBA)?

The manual is not too clear, at least for me. Can anybody tell me a step by step procedure to adjust the pitch?
Thanks
Ismael

 

[hodo]

If you are not familiar with a Max Prop, the first time you do it, you should have it out of the water. There are some small parts that are expensive if you drop them. A local guy here takes a net device with him when he does them. also, the markings are not easy to read under water. you have to line up certain marks to get where you want to be. If you do it like I did the first time, you will find it will go backwards when you put it in forward. Then you haul it and do it the easy way.{dry] Good Luck, Harold

 

[rotorhead]

Thank you very much. We can motor they way it is as long as the weather is calm. Otherwise, the boat struggles if the wind or the seas are high.
I guess I'll wait until hurricane season haul out.
ismael

 

[Loren Beach]

What Harold said!
I have watched this done, and it seemed to involve four hands, small parts, gooey grease, and a lot of concentration... and this was in the yard.

The Maxprop is a great design, otherwise, with a very slender hub, for that extra nano-knot under sail.

(External pitch adjustment was one strong reason I went with Martec when changing from a fixed prop.)

Taking the Maxprop apart under water would be quite a challenge... and if any parts are lost...

This opinion worth $.02.

Loren

 

[NateHanson]

Agreed. I actually found it very difficult to reassemble our Maxprop on land by myself. Another set of hands is much easier.

I'm amazed that someone can do this underwater, because the engraved letters that you have to line up would (I think) be so hard to read underwater! I hope he charges a lot!

Before you haul it though, make sure it's not just fouled or jammed by barnacles. You could possibly even grease it underwater to make sure that it's operating correctly (you just thread a zerc fitting into one of the threaded holes on top, and squish out the old grease (though the second hole) with a grease gun. I can't say I've used one underwater, but I can't see why that wouldn't work.

Nate

 

[rotorhead]

Nate and Loren,
Thanks....
The boat is clean, as the bottom was done in Xmas..
I'll wait until the Big H season starts; I'll have enough time to experiment..
Kinds regards..
Ismael
Erica of Falmouth
E380 hull 24

 

[rotorhead]

Repitching the 3-blade Maxprop underwater

Well guys...
I went to Tortola this week end, and consulted with Mr. Phil Oliver, from Antilles Yacht Management Ltd, Tortola, about repitching the Maxprop. We went through the schematics, and the specs from the boat, a Yanmar 3JH2E, clockwise forward rotation, a 16 inch Max 3-blade, and the reduction gear ratio for the transmission. We went step by step through the whole process, noting the hardest steps, which IMHO was the simplest one, removing the retaining pins from each Allen screw, on a silty marina with about 1 ft of visibility.

We don the SCUBA gear, and went to work. Sure thing, removing the pins was the hardest thing. We hanged a bucket with a 3 lb lead weight on the bottom, and proceded to disassemble the prop, droping all the parts in the bucket. We could see only one of the original settings (X=P), as the other one was obscured by grease. It took 30 min, step by step. After cleaning the prop from marine growth, we set the prop at the PYI recomended setting, X=S, Y=C, another 30 minutes. Took the boat out, and only could make 1,800 r's @ 4.5 knt. Back on the slip, the prop was repitched again by Phil in 20 minutes, at X=L, Y=D. Took out the boat, but this time, the engine would rev up over to 3700, but the boat would barely make 5.5 knt. Back at the slip, the prop was repitched to X=P, Y=C. This time, we hit 6 knts at 3,000, and 7 knt at 3500. I think we are almost there. We may try going up 2°, to X=T, Y=B. We'll see.

If you know what you are doing, it is feasible to do it underwater, and save the hauling expenses.
Ismael
S/V Erica of Falmouth
1997 E380 # 24.

 

[CaptnNero]

Overpropping is a serious matter. It can lead to deposits in the exhaust elbow which will increase back pressure. A diesel mechanic at a seminar said that among other things the increased pressure can cause the engine to "weep" small amounts of oil from various places. Your first indication may be oil in the bilge without a serious point source.