prop question

[feklar]

Driving a 2000fisher 18 1/2 deep v repowered with a 2002 merc 115 4 stroke, it has a Michigan aluminum 3 blade 13.75 X 15 pitch prop. Current prop has been filed a bit but looks in good shape.

I don't totally trust the tach because it varies as I drive. GPSS WOT peed is 29-31 MPH, gets up on plane pretty fast. I wouldn't mind if my WOT speed increased.

Thinking I should be carrying a spare prop, OR replace the current prop and use it as a spare.

Boat is used for fishing and I end up in the shallows and I sometimes hit things, so I'm wanting to stay non stainless.

I also use a trolling plate to slow the boat down to .9-1.1 MPH for trolling. I don't want this speed with the plate down to increase.

Suggestions (and why, I'm a prop newbie) for a spare or new primary?

If I'm going to be carrying an extra prop, what other parts from down there should I carry as well?

 

[steelespike]

Re: prop question

You really shouldn't make any changes without reliable rpm info.
We can't even tell if your setup is working with out rpm.
At this point stick with the present size and type prop.
With accurate tach info this could be an opurtunity to improve your performance.

 

[Mi duckdown]

Re: prop question

A spare prop is useless if you don't have spare nut and parts that holds the prop on.
when you drop the nut in the water.
And Oh sh..t
Gotta have both.
I zip tie the parts I need to the spare prop.
Been there, done that. .02

 

[Slow Ride]

Re: prop question

I agree with steel spike, no way to talk props without accurate RPM data. Question, why stay away from stainless if "in the shallows and somtimes hit things?" I live and fish on the Texas coast and I'm in the flats all the time hitting all kinds of stuff from sand bars to oyster reefs to the occaissional rock. I'm no expert but I can tell you that you almost cant find anything but a stainless prop down here and if you go to the docks where all the guide boats are moored, you will see stainless on every boat without exception. Perhaps its due to the salt water but I'm sure it has something to do with durability also.

 

[feklar]

Re: prop question

I've been lurking here for a while and thought if you hit stuff with a stainless prop you had a higher chance of causing lower unit damage. I'm willing to sacrifice a little performance and an aluminum prop to avoid lower unit damge.

 

[steelespike]

Re: prop question

If you are likely to make soft contact at slow speeds in the shallows they say that a ss prop will hold up better.When finally needing repair it will cost more.This doesn't include contact with rocks in the shallows.
If you make soft contact with aluminum it will need repair.Props have a cushion hub that is supposed to protect the drive train.

 

[Slow Ride]

Re: prop question

I had not considered the stress it could put on the gearbox in the event you hit something really hard. That said, I have hit a reef hard enough to knock the motor (Yamaha TRP 150) all the way out of the water! It scared the heck out of me. There was a PVC pipe with a Penzoil can on top of it for a year which marked the pass through the reef. Someone moved the pipe for some reason and I managed to hit a rock the size of my truck. To this day I can't explain how It did virtually no damage to the transom or motor. Only a minor ding in the skeg. That is what the skeg is for and for me, it worked! I was told by an "old timer" that aluminum props get used up to fast down here. We tend to run them really shallow in this area and it is very common to see lower units with the paint taken off all the way to the bottom of the shaft housing. The props on these boats (stainless) have been worn down from running through the mud and sand. Apparently the wearing happens much faster on the softer aluminum props.

A few weeks later I tried to be courteous and go around a fisherman who was parked in the ship channel under a bridge. I went outside the marked waterway, at an idle only to find more fishermen behind the protective wall of the bridge. So, I stopped, backed up and turned around to go back in the channel thinking that the guy in the channel was blocking the navigation lane and would just have to deal with a little boat traffic. While backing up I "bumped" into something at very low RPMs. When I took off and got on plane I noticed a bad vibration. When I got her out of the water I found major prop damage and a cracked lower unit. Who knows why these things happen? As I mentioned earlier, Yamaha TRP! Yep, about $1700 in new props and another $4500 for the gear case. Lesson learned, do not hit anything while in reverse as there is no skeg or lower unit to shield the prop!