2 Stroke Outboards

I am presently using a Yamaha 25hp, 2 stroke outboard. I would like to purchase a new 15 hp, 2 stroke. Mainly the reason is weight. I am trying to lighted the chores for me and the admiral to launch the dinghy.
I like the Yamaha, but everywhere I look, they only show the 15hp engine as a 4 stroke. It's still 100 lbs. plus. Any suggestions?

I shopped for a Yamaha 2 stroke in the fall of 2010 and there were some available at a dealership in Florida. I don't recall the name of the place but it kept comming up in dealership searches.
I was fortunate enough however to find a used Yamaha 15 locally (in Ct via Craig's list) that had 5 hours on it for 1800 and I snatched it up.
Keep searching, one will come up.

Conventional 2-stroke engines cannot meet the new EPA clean air regulations. The Mercury website only lists 4-strokes in the smaller size.
See: Outboard Engines | Mercury Marine

Go south. Yamaha 15 hp 2 strokes are all over Central and South America. You can get Tohatsu 2 strokes in the Caribbean. We see a few Mercury's but parts and service aren't as readily available.

Larry H said:

Conventional 2-stroke engines cannot meet the new EPA clean air regulations. The Mercury website only lists 4-strokes in the smaller size.
See: Outboard Engines | Mercury Marine

Click to expand...

^^^^^^THIS^^^^^

It is not cost effective to put all of the computer stuff on the small 2 strokes when they can make a 4 stroke without it and still be clean.

I think the law went into effect 1/1/10. I found a brand new one in 2/10 with a build date of 12/09...$2200...sold!!!

Could someone explain to me (a real rookie when it comes to engines) why 2 stroke vs 4 stroke is desired? I have only 4 stroke tools at home (mower, chipper, snowblower) and know that the oil and fuel are separate systems.

thanks,

scarletbison

Could someone explain to me (a real rookie when it comes to engines) why 2 stroke vs 4 stroke is desired?

Click to expand...

1. Weight.
2. Can be stored in any position.
3. Weight.
4. Weight.

scarletbison said:

Could someone explain to me (a real rookie when it comes to engines) why 2 stroke vs 4 stroke is desired? I have only 4 stroke tools at home (mower, chipper, snowblower) and know that the oil and fuel are separate systems.

thanks,

scarletbison

Click to expand...

Weight and simplicity....and you never have to change the oil!!!....part of the simplicity I guess. While 2 strokes can be ornery sometimes, they seem to last forever probably because the "oil delivery system" is so consistent....and they are more tolerant of lower compression. I have a leaf blower I can hear the piston banging around in there....piston slap I think it is referred to. And it has run forever and likely will continue to.

2 strokes produce more power out of less displacement because they have a power stroke on each down stroke....one of thereasons they are lighter...and can tolerate lower compression.

I love my 4-stroke dinghy. I only ever had a 2 but wouldn't go back. As for weight... think hydraulic deck crane.

Dave

Mercury 15hp is the same weight as a 9.9 mercury. I have a 25 hp Yamaha 4 stroke on one dingy and the 15 Mercury 2 cycle on the other. The Mercury pull starts easier is faster and has more out of the hole torque and it weighs about 75lb , close to half the weight of the Yamaha. Imagine my surprise when I purchased a new dingy and couldn't register it as an outboard without having a new approved 4 cycle outboard to declare as its power. I ended up registering it as a row boat and got around the DMV, It has oars right. I told them I already had a outboard and was just trying to register the boat. California wouldn't allow me to register the new boat with my old outboard. So if California is taking this stand it will effect every other state before long. I think the Yamaha is more fuel efficient but I'm really not sure of this as the Mercury is so much lighter. The Mercury has throttle handle shifting which when compared to the separate shift lever on the Yamaha is much more convenient. Also with the Yamaha you have to consciously move a release to have the Yamaha tilt or kick back with grounding and the move it again to engage the tilt lock for reverse. That was handled automatically with the Mercury. Expect to pay a premium if you can find a Mercury 15. Think need a hydraulic crane to lift the motor!! My 25hp Mercury 2cycle was lighter than my 25 Yamaha and at least twice as powerful.

My buddy just gave away his small merc...that's the same thing I've seen and heard for the last 50 years...

Sorry to merc owners...but never have had any luck with the smaller mercs...say under 75hp.

My yamaha has spent 2 nights underwater (separate occasions) in the last 5 years...still starts on the 1st or second pull. My buddies merc needed to go to the shop every time he wanted it tro start and run smooth.

OK..OK..sorry again to you merc guys...but for every success story your gonna tell me...I got dozens of the opposite.

Years ago the small Johnson/Evinrudes were hard to beat too....nowadays...I go Yammie for 25 and under and there's one of the other brands that I forget for now that is the Yammie supplier or vice versa.

Five HP in a compact package:

I've had both Yamaha and Merc 15hp. The Yamaha has been a better engine. Basically just more tolerant of the crappy gas we get nowadays. But the Merc was not a bad engine. But I did have to fight with it. The Yamaha has been perfectly reliable.

And FYI...almost all manufacturers' 9.9 and 15hp2 stroke motors are the same weight...they are the same engine with a different fuel system set up. There are conversion kits for the 9.9s I do believe.

I am with you on the 2 vs 4 stroke on smaller outboards... especially if it is on a inflatable... the power to weight ratio is a real plus. I had a 10hp yamaha that went under water on many occasions.. even while running wide open and always started easily after a rinse of fresh water. Over 25 hp and the four strokes are in their element. Find a used yamaha smoker that has done light duty in fresh water ... rebuild it if you think necessary and enjoy.
HOLLYWOOD

I'm getting great service from a 25 year old Evinrude 4.5HP.

Mark, the leak on that motor and utilitarian design screams British design to me. What make is that old 5HP in your picture?

Is it not a Seagull???

Baker said:

Is it not a Seagull???

Click to expand...

one of the more cantankerous outboards ever made... if they weighed a bit more they would of made better anchors than motors!
HOLLYWOOD

Baker said:

Is it not a Seagull???

Click to expand...

Thanks Baker. I just googled "Seagull outboard" and saw that it was British

I guess a picture is worth a thousand words

Mercury Reliability

The Yamaha may be more reliable but I hate it. The mercury 15 I have had for 18 years 1 set of plugs. I have a 3,3 Mercury that's 20 years old and it's had a few sets of plugs and a fuel shut off valve. The 25 Mercury I had for about 15 years and it suffered 1 fuel pump diaphragm. The Yamaha I've had 3 years and it has been reliable but it doesn't have anywhere near the power of the 15hp Merc. It will not plane four adults and two dogs in a twelve foot Achilles rib. It barely manages two adults and the two dogs. The Merc will plane the same load easily. The only thing the Yamaha does better is idle quietly. Which it will do for hours. No doubt it's a better trolling motor. I will say I've had the good fortune to all of these above sea level.

Scary,

You could try telling CA that you will be using an electric trolling motor on the boat. That might work.

The 25 Yammie runs ok, seems to run rough at idle and intermittant missing at high rpms, but perhaps that is just some junk in the carb. It is heavy, but the new 4 stroke 15 hp engines are not that much lighter. Maybe I'll just stay with what I have.
However, it does seem to go through gas pretty quickly. I have a 3 gallon tank on board, and it does not last that long. What size fuel tank do you folks typically carry on board your dinghy?

ChuckB said:

The 25 Yammie runs ok, seems to run rough at idle and intermittant missing at high rpms, but perhaps that is just some junk in the carb. It is heavy, but the new 4 stroke 15 hp engines are not that much lighter. Maybe I'll just stay with what I have.
However, it does seem to go through gas pretty quickly. I have a 3 gallon tank on board, and it does not last that long. What size fuel tank do you folks typically carry on board your dinghy?

Click to expand...

For a 6hp I carry a 6 gal tank..but usually never full. Seems to last a long time.

The OLD rule of thumb of fuel burn unless you know more exactly for your engine is hp divided by 10 at full throttle...so at full you are burning 2.5 per hr...call it 2 gal/hr at cruise...sound nearly correct?

Yes, 2 gal per hour sounds about right.

I carry a 6 gal tank when I cruise in the dink. The new 15 Yamaha 2 stroke is much more efficient than my old 8 hp Evinrude was. Probably because it doesn't have to work hard to keep the dink on plane.

The dink OB's I have bought used, at a dealer/service so they are in good shape and about 50% of new. Most get little hours/use. Not much to a 2 strock.

Yesterday dumped the 12 ft Livingston with the 20 hp merc in and with new spark plugs start right up and ran great. anyway might wnat to buy used?

Another disadvantage to the 4 strokes is that they will not tolerate old fuel or fuel being left in the engine for more that a week or two. I have a 8 hp nissan that I did not burn all the fuel out of the engine before storing it for the winter....bad move. Not only did the ethanol fuel attack the aluminum carburetor, ruining it, it also turned to varnish in the fuel pump. So, when I replaced the carb ($180) and hoses, stuff in the pump kept breaking loose and clogging the tiny orifices in the new carb. After removing and cleaning the carb 3 times, it's running smoothly again.

The bright side is that I purchased a 9.9 hp carb, which is the only difference between the 8 hp and 9.9 hp, and got 22%* more power.
*Per the Nissan parts tech.

So, the moral of this pathetic story is that 4 strokes do not have the large, forgiving carb jets that the 2 stroke have and always, always, always run the engine dry. Daily. Every. Day.

I think having oil mixed in the gas prolongs the life of the new Ethanol gas? Don’t seem to have/see the problem with the four 2 stroke OB, 140 hp, 20 hp, 7 hp and 4 hp. Anyway I will stick with 2 strokes.

My Mariner 2 horse is now 26 years old and still running. The last time I had it apart I had to use a generous amount of JB Weld to build up the lower end. Cannot get parts for it anymore and do not want a 4 stroke. Lookin' at that new propane powered kicker, but it is ten pounds heavier.

My Mariner 2hp dinghy motor is 24 years old. I get parts by ordering for a 2hp Yamaha, which it is really.