2 Stroke vs 4 Stroke

[tropicalescape]

Originally Posted by MarkSF

I'd replace it with a 4 stroke I think. I've had one before, it was fine. But for my application where it gets run for maybe 4 hours a year, it's not worth replacing unless it gets stolen.

The problem with 2 strokes isn't just the oil. Up to 30% of the fuel goes unburnt out of the exhaust. So at 100:1 mixture, for every ounce of 2 stroke oil, you're dumping 30 ounces of raw gasoline into the water.

30% out the exhust...Not with a reed valve type...

[sy_gilana]

On second thoughts, if this is a Catana 50, you have more than enough weightlifting capacity. Also more people carrying capacity. You could easily go for a 4 stroke 25 Hp engine on a longer dinghy. You will inevitably want to plane with 6 people in the dink.
A short <12ft dink will not do this. You should be looking at the 14ft range. Now to power THAT, you need 25 HP. The Yammie 25 is usually a 2 cyl engine, of a larger capacity, and its a bitch to pull-start if you are a small person. IF you could get your hands on a Yamaha D30 2 stroke, you will have found a jewel in the Yamaha stable. That is an over-engineered motor, 3 cylinder, easy to start, powerful as all hell, and if driven carefully not too thirsty. However, this opens up a whole new world of wakeboarding and waterskiing , and that can mean several jerry jugs hidden away in your cockpit lockers under the table.

[Wraith_Mac]

Originally Posted by foggysail

8-9HP 2 stroke vs 4 stroke, 15 2 stroke vs 4 stroke, 30HP 2 stroke vs 4 stroke are all relevant Mac. In all cases a 2 stroke is lighter. So the difference in fuel consumption IMHO is no where near as important to many where as weight might be. Of course if the engine is mounted once and stays put for years until it needs replacement then maybe fuel soars on the importance list of choice options.

Foggy,
I'm not arguing with that logic, of course there are situations when weight is THE governing factor for an individuals needs.

It is indeed the last part of your post that I'm suggesting is more in line with the OPs situation and in my opinion vindicates the choice of a 4 stroke, in his situation the small weight differences are not critical. [IMO]

The smaller under 15hp engines and any advantages attributed to them were not on his radar, hence my comment.
Cheers,
Mac

[foggysail]

Originally Posted by Wraith_Mac

Foggy,
I'm not arguing with that logic, of course there are situations when weight is THE governing factor for an individuals needs.

It is indeed the last part of your post that I'm suggesting is more in line with the OPs situation and in my opinion vindicates the choice of a 4 stroke, in his situation the small weight differences are not critical. [IMO]

The smaller under 15hp engines and any advantages attributed to them were not on his radar, hence my comment.
Cheers,
Mac

Mac--

I should not have mentioned an 8 or 9 HP at all. The point I was trying to make was that a 2 stoke anything will not weigh as much as a similar 4 stroke. And certainly, if the engine is not being often removed weight should not be a factor... we agree

[AliaVita]

Wow guys, thanks for all the comments, it really is helpful. I'm not a tree hugger, but I recycle my waste at home because it costs me nothing, I used to drive a 4.2 V8 Turbo car but I don't now, not because of the environmental issues, but because I used to get depressed every time I filled up (those of you in the states might not understand that bit. Fuel is VERY expensive in Europe). So this isn't an ethical thing for me, but I wouldn't dump anything in the sea if it was avoidable. I don't drop litter either.

With regard to the dink, I'm looking at an 11ft AB Aluminium Rib, that's actually as big as I'd want to put on a Catana 50 and as big as I need. There will rarely be more than 4 of us, hence to 15/20 hp requirement. Most of the four stroke 20s weigh exactly the same as the 15s, so I'd go with a 20. The 2 strokes seem to bulk up over 15hp so it would probably be a 15. Once you get over 15hp it seems that the 2s/4s argument on efficiency, weight, fuel, noise etc all seem to shift towards 4 strokes. As a matter of courtesy I will let you know what I decide to do when I get to the Caribbean. I have a spare roll up dinghy and a Torquedo 1003 for emergencies, so I will dump (sell) the existing rib in the Med before I leave instead of hauling it across the pond.

Thanks again guys.

[Wraith_Mac]

Originally Posted by foggysail

Mac--

I should not have mentioned an 8 or 9 HP at all. The point I was trying to make was that a 2 stoke anything will not weigh as much as a similar 4 stroke. And certainly, if the engine is not being often removed weight should not be a factor... we agree

No worries, all's good mate.
Cheers,
Mac