Maximum HP ratings

[MN Shutterbug]

I've always wondered when the maximum hp is stated for a particular boat, does it make any difference if it's 2 stroke or 4 stroke, especially on an older boat maybe before 4 strokes were around? My question is because of the additional weight of the 4 stroke. Or isn't that a factor?

[slammer]

Most new 4/stk's are lighter than almost any 2/stk of same horsepower. My 2013 150 4 stk Merc is 10 pounds lighter than the 2001 150 EFI i had.

[delcecchi]

I've always wondered when the maximum hp is stated for a particular boat, does it make any difference if it's 2 stroke or 4 stroke, especially on an older boat maybe before 4 strokes were around? My question is because of the additional weight of the 4 stroke. Or isn't that a factor?

I don't believe that is a factor. I think there is a formula that they use that comes from the coast guard.

[BobT]

Most new 4/stk's are lighter than almost any 2/stk of same horsepower. My 2013 150 4 stk Merc is 10 pounds lighter than the 2001 150 EFI i had.

I don't know if this is necessarily true. One must compare apples to apples. Number of cylinders, shaft length, etc.

Here's some comparisons I found. Granted, this was found on Evinrude's HSOforum and without knowing the exact models being compared it's nearly impossible to determine if they compared apples to apples. For simplicity I bold typed the 2-strokes in the comparison.

Evinrude E-tec 150HP 418

Yamaha 4-stroke F150 466

Yamaha 2-stroke HPDI 150 468

Mercury 4-stroke Verado 150 L4 510

Mercury 2-stroke Optimax 150 431

Honda 4-stroke150 478

Suzuki 4-stroke DF150TX 474

[BobT]

I don't believe that is a factor. I think there is a formula that they use that comes from the coast guard.

I think I would agree. I'm sure there are a lot of factors that go into the calculation.

[marine_man]

I think on "older" boats (pre-mid 1990's?) 4 stroke additional weight didn't factor in much; however, there is no "correction factor" that I'm aware of to offset as well.

marine_man

[delcecchi]

I goooogled and found this from the government

http://www.gpo.gov/fdsys/pkg/CFR-2002-title33-vol2/pdf/CFR-2002-title33-vol2-sec183-43.pdf

good place to start.

[Josh.P 86]

I don't think two stroke to four stroke will be enough weight to make a difference. Also weight isn't the only factor. The H.P rating is to ensure it is safe to handle as well. I looked into converting my side council 1660 pro v to a tiller and I could only go 67% of max H.P compared to remote steer. It was rated for 100 H.P so I could have only went to 65 horse tiller. Or change the decals.lol