5-10hp 2-stroke vs 4-stroke

[SKMT]

I know nothing about small outboards (my tender is a 14ft fiberglass skiff with a 60hp). My gf moved on my boat and is gonna start back working soon. I want to get a little auxiliary dinghy for her so I don't have to ferry her back and forth to shore 5 days a week.

Obviously new 2 strokes are banned in the US...but still can be found used. They are lighter...and the outboard will have to come off the dinghy whenever I move the mothership (which is just occasional). Is there a consensus preference amongst cruisers on 4-stroke vs 2-stroke in the 5-10hp size range?

[Lepke]

4 strokes have fewer problems.


So your girlfriend works while you stay on the boat?
Does she have a sister?

[chrisr]

personally we strongly prefer the 2-stroke as so much lighter (or more power for same weight which amounts to the same thing)

they are also a much simpler engine and far easier to maintain

2-strokes love being used and as full time live-aboads ours is used every day, hence is very reliable.

cheers,

[Compass790]

I lust for a 4 stroke, dont like 2 stroke oil in the water, dont like premixing fuel. 4 stroke uses a lot less petrol.
But yes 2 stroke lighter. if you are going to be lifting on & off boat by hand a 5hp 2 stroke would be your best bet. If you have a 10hp 4 stroke you are going to want a lifting aid unless you are young, big & strong.

[mlydon]

2 strokes are great in that you can dump them in a locker upside down (assuming you’ve run it dry) without a problem, can be lighter to pull on and off the dink, and very simple. On the downside, they STINK, you have to premix the fuel (which also stinks), and they use a lot more of it.

All that being said, I’ve owned several tohatsu 3.5’s (4 stroke) and liked them - around $900 brand new, sip gas, no smell, and is pretty smooth & quiet. you DO have to watch the orientation if you lay them down. That size motor weighs approx. 40lbs, has fwd and neutral - you spin it around to reverse. At one point, I sold it, along with the boat I used it on.

I currently have an 80’s vintage Yamaha 4hp 2 stroke. It weighs about the same as the tohatsu, has reverse (which I REALLY like), and as mentioned, I can dump it in a locker on its head. But also as mentioned, it stinks, uses a lot of fuel, and has much more vibration/noise.

If you have a place to clamp it on the rail, I’d go with a small 4 stroke - the tohatsu’s a good value (same exact engine as a mercury, just different stickers), yamaha is king of the crop, but pricey. Some folks I know have gone with the little Honda 2.3 air cooled jobs - they’re lighter at 30lbs, but to me, you’re giving up too much power for 10lbs - I’m not that frail yet.

What you go with will also depend on the dink - I’ve planed a wavetender 10 hard dink with the tohatsu, but couldn’t get a 270 zodiac zoom air floor to plane even with a borrowed 6hp - it just kind of bent instead of getting up. So a soft dink, you’re just going to be pushing it around at low speed - no need for excess hp.

Either engine in that range can be easily handled - I typically remove the motor from the transom, leave it in the bottom of the dink with a line tied to the handle, climb aboard and just pull it up with the line....same in reverse to put it on the dink. Any larger hp, they get heavy - next sizes up in new motors are 6hp, start weighing 60 plus pounds - much more hassle to handle - now you’re talk8ng tackle off the boom, a lift, halyard, whatever .

Matt

[Nicholson58]

Merc 15 Hp 2-st Mariner on our 9.5 ft Caribe. Motor is dirty, stinky completely reliable and starts on the first pull. 74#. We use a motor lift. Get a motor common to your cruising grounds.

[Don C L]

I had a 30 year old Evinrude 8 hp 2 stroke that I, and the former owner, took good care of so that it was fine up until a couple months ago. It still had good compression, but the pitting on the shaft finally meant that the seals just couldn't hold anymore and it wasn't going to work to replace the shaft. I think you'll likely find that with old 2 strokes. I have a 4 stroke now. Glad to have it.

[Jammer]

Originally Posted by SKMT

Is there a consensus preference amongst cruisers on 4-stroke vs 2-stroke in the 5-10hp size range?

The last 2-strokes in that hp range in the USA were sold in 2006.


So in practice the question is whether you would rather have a 15+ year old 2-stroke or a newer 4-stroke. You can get older 3 (+/-) hp motors that haven't been run much but many (most?) 10 hp+ motors that old have been run regularly and by 15 or 20 years old are due for things like new cylinders just because of hours.


2 stroke is lighter because there's no valve train, and can be stored in any orientation without entering hydraulic lock.



4 stroke will get significantly better fuel economy (in distance per gallon terms, about 50% at WOT and 100% at idle) and will operate at idle/trolling speed for longer without fouling the spark plugs. The fuel economy improvement means that you can use a 3 gallon tank where you would use a 6 gallon tank for a 2 stroke; you're carrying 15 pounds less fuel which makes up in a sense for the weight of the valve train. You will pollute less mainly because of drastically reduced amounts of unburned fuel in the exhaust. You will change one quart of oil every 100 hours rather than adding one quart of oil to the gas every 10 hours. Engine longevity is somewhat greater though this is hard to quantify as small outboards are discarded for many reasons other than wear and most do not have hour meters.


In practice either will push the boat

[C420sailor]

I got a used late model Yamaha 9.9hp two stroke. Swapped in a 15hp reed valve, re-propped it. Thing is an absolute monster. I have a 10.5’ RIB and it’s terrifying solo.

It’s stupid reliable, light, and I love the two stroke sound at WOT.

[Tupaia]

Tohatsu 9.8, 2 stroke, 26kgs, starts really really easily so ladies love them. On my second one first one was 12 years still managed to trade it in for a new one. Full time live aboard so used a lot.

[Simon.Sails]

If it's just ferrying to shore then a small electric outboard would probably the most hassle-free of all 3 options. 2 strokes are easy to handle, but smell and pollute too much for my taste, 4 stroke too heavy.

[Joh.Ghurt]

Originally Posted by Compass790

I lust for a 4 stroke, dont like 2 stroke oil in the water, dont like premixing fuel. 4 stroke uses a lot less petrol.

Using less petrol is a strong argument, but the concern about premix isn't that much of a hassle for a cruiser. Whenever you fill up a jerrycan with dinghy fuel, add the 2-strocke liquid at the correct ratio and be done. I never have petrol on boat that isn't ready to be used.

[radsailor]

Originally Posted by Simon.Sails

If it's just ferrying to shore then a small electric outboard would probably the most hassle-free of all 3 options. 2 strokes are easy to handle, but smell and pollute too much for my taste, 4 stroke too heavy.

I just ditched (sold) my 4hp 4stroke mercury (used with a 19foot sailboat/2000#displacement) and replaced with 3hp Torqeedo electric. It is reliable, clean, light and quiet. Your girl friend could take the tiller/throttle arm with her to work to discourage theft. Only downside is the need to charge the battery. For a dingy, you could probably use a smaller unit.

[Robhwa]

If low weight and reliability is critical, cost isn't so much a factor, and distances are relative short (<5 miles), consider an electric. I have two Torqeedos for my kayak and dinghy, and even use a Minnkota 80 lb thrust as my trolling and backup motor on my 22 ft C-Dory. The Torqeedo outboard I have weighs about 20 lb total, but I clamp the motor shaft on first, about half that weight, then put the battery on it, so I never lift more than about 10 lbs. Easy for an aging mariner. No fuel, no oil, no pulling to start, and it can be stored upright, on its side, or upside down. Theft of an outboard hanging off the back of your main boat is a serious problem in some places. I lock the Torqeedo away. Charging can be solar or from the house batteries. Expensive, though, and some people have had reliability issues. I have had none over 5 years. Frankly, I am sold. For longer distances you need a gasoline motor.

[MJH]

Originally Posted by SKMT

I know nothing about small outboards (my tender is a 14ft fiberglass skiff with a 60hp). My gf moved on my boat and is gonna start back working soon. I want to get a little auxiliary dinghy for her so I don't have to ferry her back and forth to shore 5 days a week.

Obviously new 2 strokes are banned in the US...but still can be found used. They are lighter...and the outboard will have to come off the dinghy whenever I move the mothership (which is just occasional). Is there a consensus preference amongst cruisers on 4-stroke vs 2-stroke in the 5-10hp size range?

The dinghy I use when cruising is a West Marine RU3 rollup that I used with an older Evinrude 2.0 2-cycle. While reliable when new the engine got progressively less so over time, even with the best care I could give it. I recently sold it and got a new Suzuki 2.5 HP 4-cycle...I chose it because is was the lightest of the group. It has a couple of nice features, cheap, and easy to start.

Before selling the old outboard I rebuilt the carburetor and was able to get the last parts in the Seattle area for an outrageous price which is the problem with old 2-cycle engines...if you can find the parts they will be expensive. By the way, the engine was still hard to start.

I recommend you bite the bullet and buy a new small HP 4-cycle engine with the objective of "avoiding" having to run to your girlfriend's aid every time she can't get an older 2-cycle started...it will happen!

Good luck.

~ ~ _/) ~ ~ MJH