New prop doesn't fit - trim tab is in the way

[zmoz]

I bought a new prop this morning for my '74 150hp inline 6 mercury outboard. Went from 19 pitch to 21. Now the damn thing doesn't fit...the trim tab is in the way! What do I do? Do they make different size trim tabs or something?

[mxz]

You can get a flat one without the tab or just saw your tab off. I don't think they really do much anyways except for corrosion control.

[zmoz]

I'm glad you said that...I just spent the last half hour cutting it off. :D Now I've got a different problem...the inner round part of the prop...the cylinder that the blades attach to...is to long. When I tighten down the prop nut it won't spin, because it is too tight. Is this the wrong prop?!?

[VELOCITOY]

HEY ZMOZ...You need a different thrust washer by the sound of it...If you know what type of prop it is, post it & I'll bet one of the gurus here will probably be able to give you the part number you need to make it work...These guyz know their ****e...:D ...

[baddjonny]

try the thrust hub from the old prop bet you have the same problem I just had on a old outdrive the new thrust hub is thin and fit's on a tapered shaft the old style has a much longer thrust hub with a square sholder and using the new one let's the prop go back too far and hit the carrier cover cap the old hub should work your problay using a new flow torq 2 hub.

jon b

[zmoz]

I tried the washer from a different prop - I don't know what it was from but it came with the boat. It was much thicker, and I thought it would work, but when I tightened the nut down it was still too tight. I think the problem is that the old prop would go inside of the lower unit a little bit, the newer prop has a bigger diameter and does not go in. Did I get the wrong prop?

[MarkHP]

What is the diameter of the gear case?

[zmoz]

Originally posted by MarkHP
What is the diameter of the gear case?

I haven't got the slightest idea...how do I tell?

[MarkHP]

Is the prop binding on the inside edge of the gearcase or the back face of the prop/gearcase. If it is the inside of the gearcase where the pop fits check for nicks and dents. If it is the back face then the thrust washer is too rhin for the prop.

[MarkHP]

I had a similar thing happen when I got a new prop. The thrustwasher was just a little too thin , about 1/16th inch. I added shim washer and all was fine. I was fortunate that the shim washer was splined otherwise it may rotate and cause wear on the thrust washer.

[MarkHP]

I guess I should read your post a little closer. you say the new prop is not going into the gearcase and the old one did a little. What is the diameter of the two props where they go into the gearcase?

[zmoz]

Originally posted by MarkHP
I guess I should read your post a little closer. you say the new prop is not going into the gearcase and the old one did a little. What is the diameter of the two props where they go into the gearcase?

Yes, the old prop is slightly less than 4", the new one is slightly more than 4 1/4".

[MarkHP]

Yup. That's it you have the wron prop. The new one is for a 4 1/4" gearcase. Measure your gearcase where the prop fits in, this is the size you need, usually a 3 1/2". Where did you get the prop?

[zmoz]

I got it at a local Merc dealer. Dumbasses! :mad: :mad: :mad:

Thanks everyone...

[pyro]

MarkHP, your rig sounds familiar. Isn't there a picture of it on the HS registry?

[MarkHP]

Yes. I have had the rig for about thre years but only posted this summer (just got a digital camera).

[zmoz]

Originally posted by Cigarette Guy
Is that little thing on the motor called a trim tab? When I think of trim tabs I think of the hydraulic plates that control the pitch and level of the boat.

I don't know, but that's what my (really bad) repair manual called it. Now that I've cut it off...is it going to be alot harder to steer?:)

[O/B Dude]

That is a torque tab not a trim tab. Cutting it off is fine. It does little or nothing to correct the steering torque. The prop you just got is for a standard v-6. You need a smaller diameter prop made for your size case. If you went from a 19 aluminum to a 21 stainless, thats like going from a 19 aluminum to a 23 aluminum because the stainless prop grabs better. You may not be able to turn it. E-mail aquaholic from this board. He is a prop technician at "The Prop Doctor" prop shop. He can fix you up with the right prop...new or used...at a good price.

[zmoz]

Originally posted by O/B Dude
That is a torque tab not a trim tab. Cutting it off is fine. It does little or nothing to correct the steering torque. The prop you just got is for a standard v-6. You need a smaller diameter prop made for your size case. If you went from a 19 aluminum to a 21 stainless, thats like going from a 19 aluminum to a 23 aluminum because the stainless prop grabs better. You may not be able to turn it. E-mail aquaholic from this board. He is a prop technician at "The Prop Doctor" prop shop. He can fix you up with the right prop...new or used...at a good price.

I went from a 19 aluminum to a 21 aluminum. I wanted a 20 but they didn't have any in stock. I would order one online somewhere...problem is I REALLY want it tomarrow. Hopefully I'll be able to exchange the prop tomarrow morning for the right one. I'll probably have the old 19 pitch fixed for pulling things.

[O/B Dude]

If the 21 aluminum puts you in the correct rpm range, save up for a 19 stainless. You will get better holeshot, accelleration, and top end. Stainless props are thinner, stronger, are truer than aluminum and dont get damaged nearly as easily. A 20 or 21 in-line chopper and a jackplate will increase speed quite a bit.