66 merc 500 3 blade prop problem

Hites87

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Ok so I am new to the boating world im doing a restoration on a 66 14 ft runabout while I have her apart I have some questions. The engine is running great but with only a 14 ft boat im hitting about 25 mph tops wide open on calm water. I have a 3 blade 13 pitch prop I believe. And I tried to pull one of my kids on a tube and I had alot of issue getting her to plane out so I tried the other prop that came with the boat 2 blade 11 pitch and as I suspected much worse so back to the 3 blade I went so please if any one has any advice for me please let me know. Thanks

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steelespike

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Apr 26, 2002
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19,069
Re: 66 merc 500 3 blade prop problem

I suspect you may have a motor issue.
A healthy Merc 500 should produce speeds around 30 or better.
I have a 65 500 on a 18 ft. al utility about 1000 lb all up weight with just me aboard.
Boat has a history of running 11" and 12" props.
2 blade props don't do well pulling a load an 11" 3 blade would likely do better than the 13 pulling.
The 2 blade could prove to be faster with a light load than a comparable 3 blade.
A new prop should help a little just figuring modern technology.
Give the motor a good checkup before you decide on a prop.
A service manual would be a big help.
You will need a tach; A Tinytach will work on your motor and almost any other on land or sea.
I think your 66 is easier to find props for.My 65 is different and requires a slightly different harder to find prop.
Fortunately I have 4 good to excellent props for it.
 

Texasmark

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Dec 20, 2005
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14,818
Re: 66 merc 500 3 blade prop problem

If the rest if your boat looks like your prop you need to get the barnacles off the bottom and you'll enjoy better performance. ANY crud on the hull, especially the roughage caused by barnacles will knock your top end off big time.

Mark
 

Hites87

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Re: 66 merc 500 3 blade prop problem

The engine is running good but I am looking for a tach as u have suggested and only the engine has the barnicles the hull is clean and smooth as for a new prop is the 11' 3 blade a good all around prop like for pulling the kids and just cruising
 

jestor68

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Re: 66 merc 500 3 blade prop problem

The engine is running good but I am looking for a tach as u have suggested and only the engine has the barnicles the hull is clean and smooth as for a new prop is the 11' 3 blade a good all around prop like for pulling the kids and just cruising

I recommend a Solas 11 pitch for your motor. The up to date design will work better than your old school prop. The WOT rpm to shoot for is 5200-5300.
 

GA_Boater

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Re: 66 merc 500 3 blade prop problem

New '66 500 props are just about impossible to find because of the 11 spline hub. Same prop for 35-50 hp, 1962-69. I have found one source for new props at $120. 10-15" pitch. Here

EDIT - BTW - the boat in my sig with the same 500 runs at 32 mph WOT, GPS, 10" pitch. That's at 54-5500 RPM. 48-5500 RPM is what my manual says.
 
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GA_Boater

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Re: 66 merc 500 3 blade prop problem

I recommend a Solas 11 pitch for your motor. The up to date design will work better than your old school prop. The WOT rpm to shoot for is 5200-5300.

Where? I would like to find one.
 

GA_Boater

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Re: 66 merc 500 3 blade prop problem

Opps! Forgot the 11 spline thing. Maybe if you call Solas, they will make you one with 11 splines.

Maybe they have a dusty one sitting the warehouse. :rolleyes: Actually I would love to get a hubbed prop, but again the 11 spine thing. I don't even know if an 11 spline hub was ever made.
 

jestor68

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Re: 66 merc 500 3 blade prop problem

You might check out www.propcopropellers.com.

They list mercury 35-50 hp props, 11 spline for 1962-1969 motors; in 10,11,12,13, and 15 pitches in 3 blade aluminum.

Select mercury props; fifth item down the page.

All is not lost. :)
 

GA_Boater

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Re: 66 merc 500 3 blade prop problem

You might check out Propco Marine Propellers and Boat Propeller Manufacturer.

They list mercury 35-50 hp props, 11 spline for 1962-1969 motors; in 10,11,12,13, and 15 pitches in 3 blade aluminum.

Select mercury props; fifth item down the page.

All is not lost. :)

That's the same link I put up earlier. Propco is the only source I've for new 11 spliners. According to Propco, they were the supplier to Merc for OEM props. Could be just talk, I don't know.
 
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