Merc Power for Tuffy

Report the performance of your boat, supply as much information as possible (weight, HP, prop, speed, etc.).
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Scott
Posts: 308
Joined: Sun Sep 17, 2006 3:21 pm
Location: Canada, Southern Ontario

Merc Power for Tuffy

Post by Scott » Wed Apr 06, 2011 9:58 pm

From selling my P.O.S Mercury 4 stroke to obtaining a completely opposite model - the 650XS. To trading that for 2.5 + parts of Merc 650's. Then to almost getting a In-Line Six Mark 78 short shaft Merc. Then almost getting a Johnson Stinger short shaft. To finally building a Merc 650 short shaft 1975 with all of the correct parts. Its time to mount it on the boat and hit the water.

I've further reduced my boats weight by over 100 pounds with the engine installed. Smaller battery, no stainless steel modified transom and lighter motor overall.

According to the service/shop manual for the outboard to correct prop for the Merc 650 is a 10.75 x 17 which are pretty hard to find actually. My boat over qualifies for it by being under 700lbs and less than 14'. The theoretical speed is 43-50mph. I could see 43 but 50? No chance. I also have a brand new Merc Chopper II measuring 10.375 x 18 that'll fit on my prop shaft. Even though its a poor choice since its a surface piercing prop and will generate huge acceleration lag times I've read and gotten feedback from others that it'll still be faster than a stock aluminium prop.

With the 40hp Merc w/ power trim I was getting 36mph on a good day and 38.5mph was my best on GPS. It weighed a ton, porpoised like hell and I hated it.

I'll post results with pictures of GPS later on this Spring.
Thun.der.bolt
ˈTHəndərˌbōlt

A flash of lightning with a simultaneous crash of thunder.

An ignition system of early Mercury outboards that not only is a nightmare to diagnose but also improves a marine mechanics competency.

upspirate

Re: Merc Power for Tuffy

Post by upspirate » Thu Apr 07, 2011 5:01 am

i GUESS THIS IS MORE OF A STATEMENT THAN A QUESTION.....LOOKING FORWARD TO HEARING HOW THIS RUNS!!!

Oops caps lock by mistake,but too lazy and tired to go back and retype!!! :roll:

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