4 stroke vs. 2 stroke weight and power

[Redneck]

Re: 4 stroke vs. 2 stroke weight and power

Ran the new prop today. I feel like I have a 2 stroke on now! Got on plane within 2 seconds. RPMs went up to just under 6000 wot. I think I even picked up some top end speed, but had no way to tell today.

The man, Peter, at Propco knows his stuff!

 

[ondarvr]

Re: 4 stroke vs. 2 stroke weight and power

I have no bias as to 2 stroke or 4 stroke, but comparing peak HP between the two is misleading. In trying to keep the size and weight down they need to tune the 4 stroke for more HP with as few cubic inches or CC's as possible, which can result in less low end power and response. After racing and modifying 2 and 4 stroke motorcycles for more than 25 years I can tell you there is a huge difference in the the type of power they produce.

Motorcycles are not rated by HP like a boat motor, it's by CC's. To compensate for the lower HP per CC out of the 4 stroke, they allow 250cc 4 strokes to race in the 125cc 2 stroke class and 450cc 4 strokes in the 250 cc class. At first this worked out well, but as the technology improved the over sized 4 strokes took over in each class, but still can't really compete CC for CC, but it is getting closer. The big problem with getting more HP out of a 4 stroke, is more wear and tear than when they were tuned less aggressively and the high cost of rebuilding them when they wear out or self destruct.

 

[jbjennings]

Re: 4 stroke vs. 2 stroke weight and power

My opinion, which I'm sure is INVALUABLE to EVERYONE, is that the 2-stroke is definitely the way to go on outboards 30hp or less that are the only motor on the boat. From my experience, the 2 different brands of 15hp 4-strokes I've tried didn't even seem like they had 15hp--top end or hole-shot. The 4-strokes are very heavy, and even worse (to me) they seem to stick a lot further back off the transom, giving the motor a lot more leverage to pull on the transom and making it harder to pull up out of the water. Beside that, they're hideously ugly.....I saw a 2008? mercury 25hp 4-stroke the other day and had nightmares that night! O.K.--I'm incredibly biased but do like the thought of a cleaner running, better fuel mileage outboard, but just haven't driven a 4-stroke that pleased me yet......Still hoping.
JBJ

 

[Redneck]

Re: 4 stroke vs. 2 stroke weight and power

I agree the 25hp motors are plumb odd looking in 4 stroke!

I was thinking I wanted to sell/trade out of the 40hp 4s but after the new prop I am gonna stick with it for now.

I am shopping for a used 25hp for my little john and will go with 2s.

 

[pecheux]

Re: 4 stroke vs. 2 stroke weight and power

Few years ago in a BRP dealer shopping for a 14 footer alu boat. The rep told me that if I wanted 9.9 hp 2 strokes power in a 4 strokes engine I should then shop for a 15 hp 4 strokes to have the equivalent push.