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Alpha 1 prop shaft slop

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pugetsounder

Advanced Contributor
I was switching props and as I

I was switching props and as I was trying to get the 55 lbs of torque on the prop nut I noticed it just kept turning never getting over 20 lbs. I finally stopped although the nut kept threading on. Is it possible to pull the shaft out by over tightening? I've never noticed much thread exposed at the end of the shaft with the prop mounted before.

I also noticed that my prop shaft has some slop in and out about less than 1/8th inch (not side to side) is this normal. I hope I didn't screw anything up.
 
In my book you didn't hurt

In my book you didn't hurt it; 1/8" of in/out play is OK. The different prop could make more prop shaft thread show. I change the nylock prop nut when it goes on too easy.
 
yea guy is right. when i chang

yea guy is right. when i change from my ss prop to my aluminum prop i gain about 4 threads and i just chalked it up as i dont use the spacer on my alum one
 
Thanks for the reassurance guy

Thanks for the reassurance guys. I've switched back and forth between my Al and SS props a few times and never noticed the extra threads before.

On another prop question: Both of my props are 14" 21P. At WOT my RRPMs are a bit high for the MCM470. I can red line it if I wanted to. Would I change to a bigger prop since I could go to a 15" without clearance problems. Or go for a 23 pitch? The boat is a 19' deep V it's not heavy. I'm not to worried about speed more concerned about fuel useage. I would like to keep a decent holeshot because my wife still likes to ski. Any suggestions would be helpful. I've tried the calculators but they don't take holeshot into consideration. Thanks for the advice.
 
puget that kinda strikes me as

puget that kinda strikes me as something else is wrong . the reason i say that is i have a mcm470 with the same prop numbers as you stated my boat is 18'6 and i can only achive 4500 rpm with just me in it what are you calling red line. also i might add i have the alph 1 1:84-1 yours may be different
 
"What can you get for RPMS? If

"What can you get for RPMS? If She likes skiing, you may want to try a 4 Blade 21p Alum, that'll drop you about 100 RPMs from a 3 Blade 21p"
 
"PS: The pitch for props w/fo

"PS: The pitch for props w/four blades are usually even numbered. Select a 4 blade w/1 pitch lower than a 3 blade.

Insert your data into the spreadsheet to get you close; compliments of Rod Stewart.

<center><table border=1><tr><td>http://www.marineengine.com/discus/icons/mime_msexcel.gif""" align=left alt=""application/vnd.ms-excel"">prop finder
[url=""][b]Copy of Copy_of_Boat_Speed_Finder-79780-193827.xls[/b][/url] (26.1 k)</td></tr></table></center>"
 
steve as far as the tach goes

steve as far as the tach goes which may not be right i can get up to 5100. seems really high to me. I've only taken it up once and everything seemed OK so maybe the tach is off. The boat is almost 30 years old.

brian I do have a 4 blade ss prop. it does drop things down about 100 but i think 5000 rpms is still too high for this motor. is there a way to test a tach? that could be my problem instead of the prop. I know the dashboard speedometer is off by 4-5 mphs according to my fish finder so the dashboard tach may have issues as well. thanks guys.
 
"PS:

Open the dash and clea

"PS:

Open the dash and clean w/800 grit sandpaper all of the gauge connectors and lube w/WD-40; some may need replaced due to corrosion. If you find black copper wires when replacing a connector, just clean off the black corrosion w/200 grit sand paper until the wire is shiney and then make your connection and solder it if possible."
 
I forgot to say: spray the ta

I forgot to say: spray the tachometer switches w/WD-40 and a nozzle then work them back and forth several times to remove internal corrosion.
 
It's funny I put on my aft

It's funny I put on my after market 4 blade SS prop and everything fits nicely and the nut tightens up to 55 lbs immediately. The OEM MC prop didn't want to tighten up.

Thanks Guy. Everything under the dash is pretty clean and no corrosion. I point sprayed the connections so we'll see. Maybe it's just time for a new Tach. I assume most marine tachs are electric and run off the dizzy?
 
"PugetSounder
There is a way

"PugetSounder
There is a way to test a tach but I forget the formula. What you do is get a 120v to 12v step down transformer. Put the 12v side onto the tach input and the 60 cycles will trigger the tach. Now you just have to calculate the 60 cycles/sec pulses with the tachs 4,6,8 cylinder setting. There must be some math whiz on here that will tackle the calculation.
happy.gif


Bert"
 
PS:

"I also would like

PS:

"I also would like to install a trim gauge too."

Do you have a trim sender in place on the starboard side of the OD or just a Merc. dummy puck? I think you have to pull the gimbal ring loose to slip the wires inside.
 
Bert: It sounds a lot easier a

Bert: It sounds a lot easier and cheaper just to buy a new tach! But thanks for the advice.

Brian my OEM prop doesn't have the sac hub but my SS prop does and it works great. Plus I have an extra hub just in case. It's like having an extra prop.

Guy Yes I do have the trim and tilt on my OD but I hardwired the OD to just tilt. The trim sending unit it fried and I haven't put a new set on yet. When I get around to it I will put a trim gauge on as well. As for now I don't trim at all to be safe. I do have Bennett trim tabs so no big deal on not trimming the OD.
 
"PS: I have had success w/thi

"PS: I have had success w/this procedure.

Cleaning Trim Limit Switch & Trim Position Sender

For the trim/tilt problem you are experiencing, if the wires from the limit switch (port side) and trim position sender (starboard side) are in good condition, they (Switch or sender) can be disassembled to clean out the old hardened grease. SCRIBE the sides of each one and the OD for a reference mark before removal. Clean out the old grease and pump fresh Mercruiser 2-4-C grease thru the zerk fittings before reinstallation. Clean the small brass contact points with solvent and a pencil eraser until shiny; repack w/ 2-4-C grease and reinstall by aligning reference marks."
 
Thanks Guy I might give that a

Thanks Guy I might give that a shot. That sounds a lot easier than replacing the pucks from what I've read. Pulling an outdrive just to run a couple of wires does not sound fun. I haven't really inspected it thoroughly to find out if the wires are bad or just the sending unit itself. I know the wires and solenoids inside the boat are good. Time for boating now heading out for the weekend! Hasta!
 
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