Tender Outboard: 6hp vs 8hp

[druid]

Hi
Had a kinda busy weekend around the house, and one thing I got "done" was started the old 8hp outboard in a tank and confirmed that it runs. Now it's a "seen better days" 2-stroke, so it smokes quite a bit.

I have a 8.5ft Aquamarine inflatable, rated for 9.9hp. I do NOT have a Fancy Loader - mine's "Armstrong" and subject to sore backs. So, getting the outboard off and on the dinghy is a concern.

Now, the 8hp pretty much makes that dinghy fly with just me aboard, but I had a Brig 9.5ft with a Merc 7.5, and it wouldn't plane with my Lady and I aboard. I haven't tried the Aquamarine with both of us yet, but she's not happy with the smoke thing anyway.

So: should I go to a 6hp 4-stroke? I'm guessing it would be about the same weight, maybe even a few lb lighter (ads say 55lb "dry", but I don't know what the 8hp weighs). And of course it wouldn't smoke. BUT - will it have enough power? How would a new (or near-new) 6hp 4-stroke compare to an old, well-used 8hp 2-stroke, power-wise?

If it won't plane, there's no use having it - the electric motor (Minn-Kota Max40T) gets me nearly 5 knots, doesn't need gas, is light, silent, non-polluting... I just need the gas outboard to go long distances quickly. (and let's face it: for some FUN! )

druid

 

[bananabender]

Given that the weights may be close, I would persevere with the 8hp. I wouldn't think you would lose 25% of the output and still have it run, so the 2 stroke, apart from the smoke is still a better bet IMHO

 

[tommays]

You have to be carefull NOW as motor weight has become a big issue and your dink transome may NOT be rated for the weight of 4stroke


For the most part when you jump from 6 to 8 Hp there is a big weight increase as your going from a 1 cylinder motor to a 2 cylinder motor on many 4 strokes



And 8hp 2 stroke in good condition is going to eat a 4 stroke for lunch

 

[caguy]

When was the last time you had your 2 stroke tuned? I could be wrong but they don't pump oil like a 4 stoke when they are tired. They do smoke when oil/ fuel mixtures are wrong.

 

[Tim R.]

I use a 4hp Johnson 2 stroke that weighs 33lbs. It is on a Mercury 290 rib. It can plane with just me in the middle but with the whole crew and gear it is plenty fast enough. It has the integral fuel tank but can also take a remote tank. Tiller throttle with FN gears. What I consider the perfect dinghy motor(for me)

I have always wondered why so many sailors, who love the serenity of sailing, have dinks on steroids that go 20mph.

 

[sailaway78]

Two stroke smoke

Speaking in broad terms and generalities, the primary reason a two stroke smokes is because it has too much oil in the fuel, running way too rich, or a s*(&^ grade of oil. The smoke is usually not any indication of engine wear or condition. Do a good tune up on it, clean the carb, make sure your oil ratio is correct, and use good grade of oil. I have been using a synthetic in my little dink motor and it does very well, and basically no smoke whatsoever, once the choke is off.

 

[druid]

Speaking in broad terms and generalities, the primary reason a two stroke smokes is because it has too much oil in the fuel, running way too rich, or a s*(&^ grade of oil. The smoke is usually not any indication of engine wear or condition. Do a good tune up on it, clean the carb, make sure your oil ratio is correct, and use good grade of oil. I have been using a synthetic in my little dink motor and it does very well, and basically no smoke whatsoever, once the choke is off.

I used to think that too. But someone pointed out to me: these "low-smoke" oils only don't smoke if they're burning cleanly. Low compression or weak spark will not burn the oil completely, making smoke.

As for "tune-up", there's not much to tune up in an old 2-stroke: ignition is black-box, no valves, so all you can do is new sparking-bolts, maybe mess around with the carb a bit. My oil ratio is correct (50:1), and I'm using high-grade "smokeless" oil. I hear people say 2-strokes don't smoke, but I haven't seen one yet that doesn't. They don't as much as they used to, but they do smoke, and smell bad.

I do think I'll do what I can for the 8hp and give it a Good Try this year. If it looks like I can do with less power, I'll go 6hp next year. Oh, and Tommy: true about weight if I was going 9.9. But guaranteed a 6hp 4-stroke will weigh less than a 2-stroke 9.9 (which is what the boat is rated for)

I Hear you, Tim: That's why 90% of the time I use my electric - very "sailboat-like" If you're not in a hurry, there's no reason to use a gas outboard at all. Either that, or row: I really enjoy rowing a good dinghy (an inflatable, not so much... )

druid

 

[Capt. Kermie]

I use a 4hp Johnson 2 stroke that weighs 33lbs. It is on a Mercury 290 rib. It can plane with just me in the middle but with the whole crew and gear it is plenty fast enough. It has the integral fuel tank but can also take a remote tank. Tiller throttle with FN gears. What I consider the perfect dinghy motor(for me)

I have always wondered why so many sailors, who love the serenity of sailing, have dinks on steroids that go 20mph.

It does not have to be on steroids, but it should at least be capable of overpowering a tidal current, ever tried rowing against a current? You can plane with just you in the middle?.. gee that must be fun, yet another reason for more HP.