Motor rebuilding options

"I have a 2000 40 HP mariner o

"I have a 2000 40 HP mariner outboard that I've got to rebuild. In looking at my manual, I noticed the 40 HP and the 50 HP have mainly the same specs. Is it possible to upgrade to the 50 HP by simply using 50 HP parts (carburation etc)? Years ago I changed a 10 HP Johnson to a 15 HP by changing the carburator and water pump.}}}"

"Yes, essentially the same mot

"Yes, essentially the same motor. You would need to replace the carbs (all 3 are different), and the reed retainers.

The carbs are not simply rejetted, they are a little different. Carbs for the 50 are still available from Merc for between 150-175 bucks a piece (depending whether it's a WME 68-1, -2 or -3, and as stated you need one of each).

If you can get the carbs used, it may be worthwhile, otherwise you have to trade off the cost against the very minimal performance improvement.

Moving from a 40 to a 50 horse on a given rig will likely result in maybe a 2 mph gain at wide open throttle, and only under ideal conditions.

To see a significant change in performance (7 to 10 mph) you would have to double your horsepower - moving up by 25% will have a very very small impact, and likely, the only thing you will notice is an increase in fuel consumption.

With boats, "x" % increse in horsepower does not result in "x" % increase in performance.

In general for each 50% increse in horsepower you see about a 15% increase in performance..."