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getting a few more ponies out of a 70 johnson
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<blockquote data-quote="Boat2fast" data-source="post: 340283" data-attributes="member: 13358"><p>I don't know any easy mods for the 70hp. It's tuned pretty close to the edge for a stock engine. </p><p> The Merc 3 cylinder is only around 20lbs heavier. It is available in a 90hp version. I like the way they run.</p><p> Couple of things on these 3 cylinder OMCs. The water "tell tale" on some of the earlier engines is piped low off the block. If the water pump gets weak, the water pressure can bleed off through the telltale and the block doesn't fill with water. You still SEE water so it looks OK. The top cylinder bakes from no water. This is fixed by plugging the water fitting and tapping into the top of the block like the later engines. That way water can't flow through the telltale unless the block is full. Look and see if your water telltale is piped from the top of the block or down near the bottom. </p><p> Also, ignition timing and carb synch is everything on these. It's the difference between an engine you love and one you hate.</p></blockquote><p></p>
[QUOTE="Boat2fast, post: 340283, member: 13358"] I don't know any easy mods for the 70hp. It's tuned pretty close to the edge for a stock engine. The Merc 3 cylinder is only around 20lbs heavier. It is available in a 90hp version. I like the way they run. Couple of things on these 3 cylinder OMCs. The water "tell tale" on some of the earlier engines is piped low off the block. If the water pump gets weak, the water pressure can bleed off through the telltale and the block doesn't fill with water. You still SEE water so it looks OK. The top cylinder bakes from no water. This is fixed by plugging the water fitting and tapping into the top of the block like the later engines. That way water can't flow through the telltale unless the block is full. Look and see if your water telltale is piped from the top of the block or down near the bottom. Also, ignition timing and carb synch is everything on these. It's the difference between an engine you love and one you hate. [/QUOTE]
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getting a few more ponies out of a 70 johnson
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