Can You Change A Propellar While The Boat Is In The Water?

[UNCIVILIZED]

To remove all worry about losing parts by dropping them, some guys will hang XXL white bed sheets, a good distance underneath of the area surrounding the prop.

As to the key, when it's out, it wouldn't hurt to break out your dial calipers & write down it's specs. That way, after this job's done, you can go & have a couple of spares made now, just in case. For the next time I mean.

Also, if you keep your eyes open, & or post some wanted ads, you can typically find used Max-Props fairly inexpensively. They have Great thrust in both directions, plus, you can re-pitch them without having to remove them from the shaft.
Thus you can match them up to your engine & hull form, for maximum output & fuel economy fairly easily.

Ah, & Max-Prop offers a service to recondition used/older/worn props to as new condition... for a fee. Still, it's better than tossing out a worn, but quality bit of kit.

[fstbttms]

Originally Posted by UNCIVILIZED

To remove all worry about losing parts by dropping them, some guys will hang XXL white bed sheets, a good distance underneath of the area surrounding the prop.

Bedsheets are for amatures.

[UNCIVILIZED]

Originally Posted by fstbttms

Bedsheets are for amatures.

So then yours is only for breaking in/training new guys, right?

[fstbttms]

Originally Posted by UNCIVILIZED

So then yours is only for breaking in/training new guys, right?

No, mine is used when I install Max Props. No other prop is complex enough to require a "safety net", for this experienced installer. And I don't let rookies do that kind of work for me.

Plus, I wouldn't be caught dead dragging a soaking wet, filthy bedsheet around with me.

[cmcguinness]

I think its more than a marginal gain in power. My engine specs are max at 3500rpm, so optimal operating range around 3000-3250rpm. Currently with the folding prop the engine maxes out at ~2600rpm. I think with the original propellar I can run the engine in its desired range improving efficiency and power. I don't anticipate loosing too much speed from drag, a fraction of knot at most I would imagine. What do you think? Do those number make sense to people? This is mostly from my own reading and casual advice from an engine mechanic. Thanks

[Scout 30]

Your folding prop has too much pitch. You should be able to attain max rpm at WOT. Over propping causes stress & is not good for diesels. The general rule is 1 inch of pitch equals 100 rpm. A prop shop can change the pitch on a fixed blade prop if its not too significant a change but I don't know about a folding prop. If it's adjustable I would try reducing the pitch before replacing it.

[hellosailor]

It can pay to confirm that particular folding prop IS the right one for the boat. Often someone has the wrong prop on, period.


But even if you are alone, please DO take the engine key down with you, or put it in an envelope and put a "DO NOT START" tape over the switch. People find the oddest reasons to start up engines while they can't see the guy who has his hands or head at the nasty end of things, like on the prop. Make sure you can't win that lottery.


It can also help to take a mesh diver's bag or mesh laundry bag down with you, to keep all the parts in it while you are working. No need to fumble or drop them that way. And to wear a neoprene "helmet" or at least, a couple of wool caps, which provide a surprising amount of padding if you are working where any swell or buoyancy problems keep tapping your head on the hull.

[fguptill]

I recommend against changing the prop in the water. I hired a diver in Miami to replace my prop. A few months later the prop fell off in deep water, costing me a 2 week haul out plus $3,000 for new prop and shaft.


Sent from my iPad using Cruisers Sailing Forum

[fstbttms]

Originally Posted by fguptill

I recommend against changing the prop in the water. I hired a diver in Miami to replace my prop. A few months later the prop fell off in deep water, costing me a 2 week haul out plus $3,000 for new prop

In-water Max Prop installation is not a job that the average untrained hull cleaner should attempt. Unfortunately, you apparently hired someone who didn't know what he was doing. A properly installed Max Prop requires so many failures to occur before it could fall off the shaft that it is highly unlikely if not nearly impossible.

To others- PYI can recommend qualified installer divers in your area.

[Randyonr3]

Originally Posted by cmcguinness

I think its more than a marginal gain in power. My engine specs are max at 3500rpm, so optimal operating range around 3000-3250rpm. Currently with the folding prop the engine maxes out at ~2600rpm. I think with the original propellar I can run the engine in its desired range improving efficiency and power. I don't anticipate loosing too much speed from drag, a fraction of knot at most I would imagine. What do you think? Do those number make sense to people? This is mostly from my own reading and casual advice from an engine mechanic. Thanks

You might find that the whole system has been researched prior to you owning the boat..
Reason being, If your max is rated at 3500 , the prop should be pitched at a point where it stalls the motor about 200 RPM less than max. (this is NOT my openion, its from MAXI PROP) , but while talking to other cruisers you'll find that most motors run really smooth and use best fuel at about 2/3 of max RPM.. Ours runs best at about 1800 to 2000 for long distance motoring..
If your prop is stalling the motor at 2600, the previous owner might have pitched it at just a few hundred over of what he normally would opperate the motor........