Think I need a new Prop

[c130king]

Got in about 2 hours worth of sailing today and while looking over the stern to ensure the rudders were still down I identified a "rip" in one of the blades of my prop.

The rip is on the edge and is probably 1-inch long and 1/3-inch wide. THe rip is bent almost completely backwards. Additionally there is a pretty good nick further up the same blade edge towards the hub.

I have no idea how this happened...really. Obviously I hit something at some point in the last few days.

I will pull the boat out of the water later this week and remove the prop and see if I can "bend" it back into shape. But as this is the second incident with my prop and it already has scars from a previous incident I am thinking maybe I should get a new prop.

There is a sticker on the engine that says 12 x 22 and 1.83 gear ratio. Anybody else have a 40 HP Mercury 2-stroke?

I can't seem to find a 12 x 22 three bladed prop on the WM website. Anybody able to offer thoughts/opinions/guidance on my options for props.

Thanks,
Jim

[James V]

You can check with a prop shop but it looks like a new prop is needed. Check with the local Mercury dealier.

The SS is more duarable but if you hit something really hard it can break the transmission. All of the water police boats in Florida use SS props.

[Robert]

c130king, your 40hp if it is pushing a Mac26 will need a very low pitch prop. Tell your Mercury dealer to find a prop suited for pushing a 3000lb. pontoon boat or small houseboat. Your 1.83:1 gear ratio is why you need the low pitch. Your high thust prop will have big wide blades for a good grip on the water.
..
If you really do have a 22 pitch prop on there now, you will notice a huge improvement in motor smoothness, power and control when you get a low pitch high thrust prop instead.
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The Tohatsu / Nissan prop that is 7.1 pitch with 4 bladed would be ideal. If this prop could be adapted to the Mercury 1.83:1 gear ratio outboards it would be a good prop.
..

[Night Sailor]

I have a Merc 50 2 stroke. I have tested many props and find that one must have a low pitch to reach max rpms at WOT as recommended by the factory. I'm currently running a four blade for heavy loads, slow cruising, or a 3 blade for no ballast faster travel. I happen to have a few props left over from the testing. All in excellent condition if you are interested. A Mercury Black Max aluminum 11x11x3 13 spline for your two stroke, (it gives me no ballast speeds of 15 mph at 5200 rpm.) and a Comprop comp that is 10x10 x 4 also 13 spline as a backup. Contact me by private message if you want to comment.

[delevi]

You can also get the prop rebuilt for a bout half the cost of a new one, however, the 22 pitch does sound ridiculously high, so you may be better off with new. SS prop in my opinion isn't worth the money for these relatively low HP engines, and as already mentioned, better break the prop than the engine. Most boaters will ding a prop sooner or later, so again, the extra money for an SS prop just doesn't make sense to me.

[James V]

delevi - The SS prop will not be heard with sand or hitting something in the water like other metals. They do stay clean looking longer and thus performs better in the long run. It all depends on where you cruise in.

Hitting sand with a SS prop will do no damage.

[Moe]

It's doubtful you have a 22" pitch prop on a small foot Merc. Take the prop off and look at the front of the hub for the size cast in it. As Robert said, with that high gearing in the small foot Mercs, designed to be pushing a lightweight fishing boat at high speeds, you'll need a low pitch to compensate for the weight of the Mac.

[Terry]

One would be amazed at what those prop shops can do to a badly damaged prop. I saw some of the before props on a shelf there and asked the guy if they were really repairable and he said with all confidence, certainly!. They looked well beyond repair to me! Anyway it is less than half the replacement cost and I cannot imagine a 22 pitch prop on a 40hp merc, must be some mistake. The reair shop can accurately ascertain the existing pitch and change it. When I have spare money to burn I'd like to buy a SS prop but they are 3 times the cost of aluminum.

[c130king]

I have found a sucker (I mean a friend) to go help me take the prop off. I will look at it more closey, maybe I was mistaken on the 22 pitch thing.

I know that I do have the"Power Thruster" on my engine (installed by the PO). Don't know if that makes a difference.

Whatever my prop size is it seemed to work pretty good. I could hit 16 mph with two people on fairly calm water. 13 mph with ballast in and two people.

I also normally could get around 5200 RPM at WOT. With 4 people on board I would normally only get around 5000.

I definitely don't want to waste money and get a prop that doesn't end up working. I will probably just get another of whatever I got since it works okay for me.

Thanks for all the advice. I will let you know what I find out in a few hours.

Thanks again,
Jim

[c130king]

Got the prop off pretty easily. Can't get the pictures from the camera to the computer just yet (my friend is workig on that problem).

The sticker on the engine definitely says 12 x 22. There only seems to be a part number on the prop itself. No brands or names or anything else.

48 42738A11 8P

I assume it is a Mercury Marine Prop.

I will take it to the prop shop tomorrow and see what they say. I will try a lower pitch prop if they are willing to let me try it out and return if it doesn't work or if they can give me a loaner prop or something.

But I am leary of going to a new pitch when my old pitch seemed to work just fine.

Jim

[Bobby T.-26X #4767]

the reason why it might be a 22 pitch is because it's a 12".
that is, the 40-60hp Merc BigFoot accomodates a 14" prop (which most prefer). when using a 14" prop, you need a 10-13 pitch.
by going with a 12", i suppose that a 21-23 pitch could work.
it obviously has been working for c130king.

Quicksilver Props

Bob T.
"DāBob"
'02X w/ '04 90-TLDI (14" x 11 pitch)
Dinghy Motor: '06 2.5-Suzuki

[Moe]

There only seems to be a part number on the prop itself. No brands or names or anything else.

48 42738A11 8P

I assume it is a Mercury Marine Prop.

That part number (not including the 8P on the end, which is the pitch) is a Mercury/Mariner 25-60HP non-BigFoot, 12-1/2" diameter, 8" pitch, 3 blade, aluminum Black Max prop, retail $145.99.

48- 42738A13 is just like it, same price, but with extra cupping for better grip. But it would result in lower max rpms, and I don't think performance would be as good in reverse.

48- 87818A11 is a 12-1/4"" diameter x 9" standard cup, same price, but again, would result in lower max rpms.

Reference: Mercury Parts Express website.

Hope this helps,
--
Moe

[edit] It just occurred to me and I forgot to mention... the 12-22 is usually the number of gear teeth on the input and output gears.

[c130king]

Moe,

Are you saying this is a 12.5 x 8 prop then?

Thanks,
Jim

[Moe]

Yep.

Defender shows it in stock for $128.99, plus shipping (no tax).

http://www.defender.com/product.jsp?&id=53633

[c130king]

Moe,

You are awesome! That is why I love this website.

I think I figured out what happened. I have a "power thruster" (http://www.powerthruster.com) and I noticed that one of the bolts/locknuts was missing when I got in on Sunday (I thought locknuts weren't supposed to come off). I bet when nut worked its way off and the bolt started backing out the prop caught on it and got ripped. I just didn't notice the rip until Tuesday.

Thanks again,
Jim