posted 04-30-2015 01:00 PM ET (US)            

On my boat with both engines there was never a problem getting on plane, running on plane, or handling any sort of seas. I would presume that a single 135-HP would give equivalent performance to twin 70-HP engines, and, on that basis, I believe a Honda BF135 would "work out" for your REVENGE 20 W-T. Regarding the ultimate top speed, as I recall my boat would not quite reach 40-MPH. If your boat hits 40-MPH with the single 135-HP I would say you are getting very good results.

Regarding the change in fuel consumption that will occur if you change to a modern four-cycle engine--particularly a Honda--compared to what you have been experiencing with your "gas-guzzling Mercury 200-HP 1991" outboard engine: there is a great deal of anecdotal reporting that a c.1990 Mercury V6 2.5-liter two-cycle engine has excellent fuel economy and it is often described as being much better than other makes or models or brands of comparable two-cycle engines using the technology of that time.

I don't agree with that representation, but it has often been made, particularly by owners of Mercury engines who seem to have a special relationship with Mercury as a brand. If you believe the representation that a c.1990 Mercury 200-HP V6 is delivering good fuel economy, you might be inclined to think you won't see much change by switching to a modern engine like a BF135.

What I anticipate will be found is something along these lines. The new Honda four-cycle engine will consume significantly less fuel. This savings will be due to several factors:

--having less horsepower, at full throttle the Honda will consume less fuel than the Mercury because it makes less power; of course, the boat will be going slower, as well;

--at any throttle setting producing equivalent power, the Honda will consume less fuel because it is more efficient at converting fuel into power than the Mercury throughout its power range;

--the difference in efficiency will always favor the Honda over the Mercury. The amount of difference will be the least in the region of operation where the Mercury had its best efficiency, which was about three-quarter throttle or cruise speed; the difference will be the greatest at low engine speeds, such as the speeds used in angling when trolling. At low engine speeds the advantage of the Honda over the Mercury will be the greatest and will be on the order of a reduction in fuel to less than half of what was previously used.