9.9 vs 9.9

[longshanks]

this weekend I had an opportunity to test 2 different motors under the same conditions. I tested them with my (heavy) brother, his (heavy) dog, and fishing gear, in a 13' Valco aluminum boat that is rated for 20HP.

The first was an '08 Mercury 4-stroke, @ 84lbs. It took about 12 seconds to plane out, and didn't seem to reach full RPM with the heavy load. I wasn't able to measure top speed, but if it was going much slower it would have fallen off plane.

The second was a 90's vintage Nissan 2-stroke, which weighed approximately 90lbs. It took about 5 seconds to plane out and it seemed to be going 15-20% faster at WoT than the other motor.

Given that we were using these 9.9s to push a hull that is rated for twice the power, I expect that the 4-stroke wasn't operating within it's normal RPM range, and therefore wasn't performing nearly as well as the 2 stroke.

So, assuming 2-stroke/4-stroke horsepower is equal, if we had the chance to test those 2 motors on a hull rated for 9.9hp, should they not push it about the same speed, with similar holeshot?

 

[pootnic]

Re: 9.9 vs 9.9

No.
There not the same,weight,displacement,gearing,2/4stroke,etc,etc...
They might be close to the same top end speed(eventually) but thats not a for sure thing either.

 

[Whoopbass]

Re: 9.9 vs 9.9

I don't know why the Merc was such a dog. I have had three 4-strokes over the years from 5-10 hp and they all seem to perform about the same as a comparable 2-stroke of the same hp.
I doubt you achieved 22-24 mph with that heavy of a load unless that Tohatsu had cheetah blood mixed in the gas instead of oil.
18 mph would be more like it. My 15' tin boat with 25hp motor and an identical load like you had will only do around 25mph.

Maybe the Merc couldn't handle the load. If you would have kicked your Bro out I bet it would have performed pretty even with the Tohatsu.