2-cycle vs. 4-cycle maintenance

I will be buying a new 60-75 hp outboard in the next few months. Most brands seem fairly reliable these days. Price is an obvious discriminator in choosing as well as weight and availability of service, but what about maintenance? I have an Evinrude E-Tec already; how does 4-cycle maintenance compare? What does winter storage entail? Any other features I should be focusing on?

 

I guess you have to factor in what scheduled maintenance to maintain your warranty coverage is going to cost you over the term of the warranty, comparing a four-stroke to your e-tec. Don't know about USA, but here they feast heartily on people following service schedules.

 

4-stroke means lower fuel consumption, lower noise, less pollution, higher weight, higher price. And yes, there is some maintenance involved, like an annual oil and filter change, but that is hardly a reason to decide against it.

2-stroke engines spill unburnt fuel, even the sophisticated ones with injection pumps that claim to be as efficient as 4-strokes. Whether or not that is a decisive factor depends on the number of engine hours per year. For the difference in purchase price you can buy a lot of gas!

 

Minimal difference between fuel consumption of 4-strokes and direct injection 2-strokes by all reports, though you have to factor in the oil used in the 2-stroke, which also may give a whiff of fumes in some circumstances. But you never have to "change the oil". I don't know whether there is a technical reason that would give greater longevity to the 4-stroke, but it seems to be the popular perception.

 

In the berth next to mine: Mercury OptiMax 250 Pro, SX (I guess) mounted on an open Italian 25 ft boat since 2010. The owner says it burned 20 gph while everything was still in pristine condition.
But early in 2012 some rain found its way into the fuel cap, then was sucked up until the engine stuttered and the alarm beeped. The Mercury tech was called and diagnosed a shot injection pump. 2 weeks and $1800 later the engine was declared OK. Within 30 days they owner limped home on his 30 hp spare engine: another $1800 pump failure.

The guy can afford it, but he completely lost interest in the boat, so it rots away at the jetty now. Sometimes he sends a friend over from the mainland who takes the boat for a ride to charge the batteries. The engine sounds as if there are some loose nails inside.

 

Optimax has pretty good reputation, though some say a bit noisy. Fuel flow of 20 gph is either wrong or he is running flat chat, which will return bad figures in any kind of engine.

 

Unleashing all horses results in 23.3 gph, at least that's what the manufacturer states here:
http://www.mercurymarine.com/engines/engine-tests/boat-house-bulletin/?ID=692&

In metric that is .35 liter or 300 gram for each horse. Not bad for a 2-stroke engine is it :?:

 

Fuel consumption goes off the chart when you go beyond about 75% of peak revs, as a cruise setting.

 

My 50 hp Evinrude E-Tec burns about one gallon per hour in mixed usage. That is so much less than the old OB engines that I question whether a 4-cycle can be significantly better. I did not realize that 4-cycles are more expensive than 2-cycle, although, given that they are somewhat more complex than a 2-cycle, it would be understandable. Can I summarize that maintenance is slightly more on a 4-stroke but not enough to be very significant?
Living in mountainous Colorado makes for a short boating season; we still have a snow skiing slope open this weekend. The mountain lakes are beautiful (and cold). We also have few boat dealers, so I am wondering if the market for buying an OB engine here is competitive. I was quoted $7900 for a Yamaha 60 hp and $8300 for a Yamaha 70 yesterday by the only dealer in the area. I don't mind spending money as long as I am getting value, but it is hard to get competitive bids here.

 

With a new Yamaha you can better enjoy the quiet mountain lakes and cause less pollution. Here in Europe 2 stroke engines are banned from a number of lakes for environmental reasons.

 

"I don't mind spending money as long as I am getting value, but it is hard to get competitive bids here."


New engines are shipped in very good cartons.

I would look at the internet and have what you need shipped.

You WILL get resistance at factory servicing from the dealer you didn't purchase it from.

 

You might get resistance on warranty claim servicing, for which the manufacturers pay dealers a lesser amount than the dealers are able to charge Joe Average for normal servicing.

 

If your looking for a technical answer, heres my take on it.

Due to the physical construction of a 2 stroke, the piston rides on about 5% of the cylinder wall whilst near the bottom of its stroke, whilst all the ports are open. Once the piston rises up above the level of the ports and compression begins, only then do the rings ride on 100% of the cylinder wall area. A 4 stroke piston and its rings on the other hand, rides on 100% cylinder wall at all times.

So, the rings wear quicker in a 2 stroke from being in contact only with the bridges between ports, which is only a fraction of the full cylinder circumference.

When i was racing 2 stroke motorcycles, the recommended piston ring replacement interval was 20 hours. These are much higher performance engines than an outboard motor, but still it highlights the very rapid wear 2 stroke piston rings are exposed to.

When we changed to racing 4 stroke motorcylces, the issue then became checking the valve clearances, the piston rings didnt have to be checked for the entire season. With our overhead cammed, 5 titanium valved engine, the manufacturer (yamaha) provided shims to be added when clearance became excessive. Checking was very simple, just removing the head cover and checking the clearances with feeler guages. Usually they did not need adjusting for an entire season either, but milage may vary... you could usually hear the engine becoming noisy (tap tap tap) and so you knew when you were overdue for checking and shimming the valves...

After racing with both, owning both 2 stroke and 4 stroke outboards, its 4 stroke all the way for me... i swing my own spanners tho, i dont pay people to do it for me so i cant comment on how much a dealership will sting you for servicing.

 

Thank you for the comments. After posting yesterday, I found a website (NADA) which listed prices for OB engines- list price, average selling price, bargain selling price; isn't the internet great! It is easy to order a small engine, up to 20 hp, to be shipped to you but the dealers want to install the larger engines they sell. It's probably a liability issue. The difference between list price and low price can be $2K-3K. OK, I'll start looking more widely for dealership prices, and concentrate more on a 4-cycle engine deal.

 

Interesting comments by Groper about ring wear. Rings on 2-strokes are "trapped" so they don't catch the ends of the ring on the ports, so the same part of the ring is always travelling over the same part of the bore, which should mean differential wear on the part meeting the ports, though I can't say I have ever noticed it to the naked eye upon inspection.