Mercury 50 Hp

Hey, i have a mid 70's 50 hp merc and i was wondering, what is the max pitch prop i could put on it under the following conditions. it is a 14 ft aluminum, i dont know the rpm, and under normal condtions, drive alone, the boat is light, and i have a 14 pitch prop right now, it tops out at 33 mph, and has no trouble. i was wondering what prop pitch might be best, what can i go up to?

thanks

fishmonger.33

Re: Mercury 50 Hp

I think the max offering is 17. If you have a bare-bones flat-bottom it might work. Otherwise that 14 would've been my recommendation.

Re: Mercury 50 Hp

fishmonger.33 said:

i have a 14 pitch prop right now, it tops out at 33 mph, and has no trouble.

fishmonger.33

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Not sure what you're basing your statement of "has no trouble" on. Maybe it's years of no engine trouble or maybe its the sweet sound.

It sounds like you weren't the one that chose the prop you have now. Did the prop and motor come with the boat. If so they were probably matched.

Changing your pitch can affect your rpms. According to a post on the FAQ board a change of 3inches on the pitch could change your rpms by possibly over 400.

Pitch Recommendations:As a general rule, 2 inches in pitch change will result in a 350-400RPM change. EXAMPLE: A 15 inch pitch prop turns 5600 at WOT. A 17 inch pitch on the same engine/boat would turn about 5200RPM at WOT.

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http://forums.iboats.com/showthread.php?t=158083


Combine that bit of information with the information on the following FAQ and you might want to look more before you leap.
http://forums.iboats.com/showthread.php?t=158075

I've got a much heavier 16' fiberglass boat with a 50hp that runs about 30mph at a WOT of 5300 rpms with a 10-3/4 by 12pitch prop. The recommended WOT for my 1971 is 4800 to 5500 rpms.

Some people don't care about tachs but they are pretty handy when you start changing props.