Originally Posted by
JohnsonM50
With low power to be more the goal than speed the best way to achieve that is a prop change. 10 is pretty low but 9 to 9-1/2 P might do it. You might not be sacrificing much speed either because alot has to do with how much the load will allow the motor to gain RPM's. The motor works best in the upper area of it's range & is really hammered when pushed too hard at lower R's.
Being stock you want to check your syncronizing of timing to throttle, it's an easy adjustment. Also look at the economizer adj, [be sure the carb actually gets to WOT] As for carb size I've tried many OMC single barrels, 2 barrel from a 90 & 85, for all the 2 barrel effort & got 1 MPH under the best single barrel. It's no surprise that the ones that worked best for me are the ones made for the motor. I've also modified several singles, added hi speed jets, removed the choke plates & plugged the shaft holes. I've taken a router & carbide bits to the throat, beveled 1 to act as a velocity stack & round overed several. For working with what you have, the plate-less 30 carb interests me, that's what I'd try 1st ,then the older plate style.
Is the 25 on the same transom setting as the 30 was? Do you have actual RPM & speed #'s ? It's hard to tell without altho the grunt difference would be more noticeable than speed.
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