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Outdrive limits

A

Abel Crosby

Guest
"I have a old 1974 Mercruiser

"I have a old 1974 Mercruiser R-Style outdrive, gear ratio 1.98 rated for 120 or 140 horsepower. I have put a new 165 horsepower inline 6 engine in the boat. Will my outdrive withstand the added pressure? Will it add too much pressure if I buy a prop with 2 more inches of pitch?"
 
"Don't know what an R styl

"Don't know what an R style drive is.
My book shows the 120 140 and 165 all used the model 1 drive for those years right up to 1981. For that matter the same model was used (in different gear ratios) for V-8's up to and including the 260 hp GM small block.
So I don't think you will hurt your drive, and 2 inches more pitch will make no difference.

Rod"
 
"Makes sense. I found a websi

"Makes sense. I found a website that showed me the different gears in different ratio combinations I just never put it together. In your opinion, What max horsepower, prop pitch limit should I not exceed? (I would really like some more speed out of the boat if I can)"
 
"With the 1.98:1 ratio,......

"With the 1.98:1 ratio,......

You might run out of available pitch in props before you get your WOT rpms down to a reasonable 4200rpms with that motor......

All you can do is Try it,+ See......
I Doubt that 2" is going to be Enough........"
 
I'm just a little nervous

I'm just a little nervous on shearing gears or doing internal damage to the outdrive. Think it'll take the pressure if I crank the pitch up?
 
"Abel;
Here is a link to a sp

"Abel;
Here is a link to a spreadsheet that will help you to find your boat's top speed with the current power, as well as the best prop for you to use.

Have fun,
Rod

<center><table border=1><tr><td>http://www.marineengine.com/discus/icons/mime_msexcel.gif""" align=left alt=""application/vnd.ms-excel"">Boat Speed Finder
[url=""][b]Boat Speed Finder.xls[/b][/url] (20.0 k)</td></tr></table></center>"
 
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