1990 alpha one mercruiser 3.0 prop

dlogvine

Master Chief Petty Officer
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May 4, 2015
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832
i bought a nice stainless steel M14 1/4X18 3 blade prop to replace my old beaten up aluminum prop. It fits the recommended specs for such an outdrive, but when i installed it it is hitting the fin on the outdrive. Is there anything i can do with the outdrive to fit the prop and could this prop in general be used with alpha one outboard? Also the prop does not have a manufacturer stamp, so how can i find who made it and what does the letter m stand for in the prop specs?
Thx, any help is appreciated
 

tpenfield

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Jul 18, 2011
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17,620
There should be an 'offset' tab anode available for the outdrive that is designed to clear props with a high amount of rake.

Can't tell you much about the ID numbering other than it looks to be 14.25" D x 18" P
 

steelespike

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Apr 26, 2002
Messages
19,069
What is the size of the old prop?(usually near the base of the blades or under the prop nut.
What was the wide open throttle rpm when the old prop was relatively good.
You may find the new prop performs much differently than the old prop on its best day.
This will likely be good but may be disappointing.
 

dlogvine

Master Chief Petty Officer
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May 4, 2015
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832
Replaced the anode trim plate and the new prop fits as it was born there. Also it gives me a perfect wot 4500-4700 rpm. Much better than the old prop. Had some trouble with taking the old anode plate, but managed to resolve it all. Thx guys
 

steelespike

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Apr 26, 2002
Messages
19,069
Replaced the anode trim plate and the new prop fits as it was born there. Also it gives me a perfect wot 4500-4700 rpm. Much better than the old prop. Had some trouble with taking the old anode plate, but managed to resolve it all. Thx guys
Sounds good but would be interesting to know the gps speed at wot.
 

steelespike

Supreme Mariner
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Apr 26, 2002
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19,069
The numbers look pretty good but an 18" should be over revving with a light load.
unless the boat is a 20' cuddy.
If you want to refine your setup you could do a lightly loaded wot test run, pin down the rpm and gps speed.
to a specific number.
 

dlogvine

Master Chief Petty Officer
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May 4, 2015
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832
The boat when I measured the RPMs and speed was loaded 4 people and their swimming skiing stuff, will try with a light load next
 
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