Great Debate: 4 stroke vs. 2 stroke - MPG

[Beaver]

You can put a $10,000 motor on the back of a $5000 boat and you still pretty much have a $5000 boat. On a resell and operational level its hard to justify (financially) replacing a good running two stroke with four stroke. I happen to love old two strokes.

[eggsuckindog]

You will never be able to make it up in fuel savings - complete myth. You are getting very good burn rates, I'm close to Don's.

The new advantages mentioned are also offset by the fact that the new DFI 2 strokes met all the same criteria vs 4S. Not that they are any cheaper mind you but 4/5 mpg is very attainable on both but maintainence and fuel is a wash.

[Bushwacker]

Your original question didn't fit your answer, so I changed the question to what I think you really intended to ask! There are really 2 separate issues here. 1. The one in the new title above. 2. New 4 stroke vs. new DI 2-stroke?

I think you've answered question 1, the new vs. old issue, pretty accurately! You'll NEVER be able to recover the cost of a new motor simply by a ~10% reduction in fuel cost with the slightly better efficiency of the new motor on a typical recreational boat! You're already getting pretty decent mpg, which just stretches out the payback period even further! It's the same basic issue as trying to decide between gas or diesel, with 2-3X more cost for a ~20-50% efficiency improvement, on a new bigger boat! I went through the same thought process when I was contemplating a repower on my boat, trying to decide if I should replace a reliable, good running 31 year old 2-stroke with a new motor that would cost over twice as much as I paid for the original rig! (albeit in MUCH LARGER 1975 size dollars!) The bottom line is, unless you use the boat nearly every day for something like dive charters or commercial fishing, the fuel savings is insignificant!

There's a more important and difficult cost/benefit analysis that nobody on the forum can do for you: i.e., is the benefit of (fill in the blank here . . . less noise & smoke, smoother idle, more power, improved reliability and parts availability, etc.) worth all that cash and extra weight?! (Even the new DI 2-strokes are a lot heavier than the old ones!) In my own situation, I had run the old motor for so long that I was simply tired of all the noise and smoke and premixed fuel hassle that I was ready for some newer technology! Also the ethanol issue can be a problem for the older fuel systems not designed for it. However I also did some boat shopping to see what sort of boat I could end up with for equivalent $. (the cost of a new motor & bracket added to what I thought I could get for my current boat.) I found that I could get something BIGGER and maybe a little newer, but I concluded that NOTHING (with the possible exception of a repowered Moesly 21!) could match the unique combination of seaworthiness, trailerability, and cruising amenities of a 20' Seafari with a new motor and a bracket! The old motor also had an aftermarket power trim system that had died, for which parts were no longer available. And despite good compression, with over 1000 hrs on it, cold starts required use of starting fluid, and I suspect it needed new reed valves, which was a lot of $ to put into such an old motor. Basic reliability was not an issue, because I knew that old motor so well I could tell whenever it needed attention and it was so easy to work on that it never left me stranded; I could always get it going whenever I did have a problem. Although the new motors are very reliable and run great, they're not nearly so simple and easy to work on!

As for question No. 2, the issue of NEW 4 strokes vs. DI 2-strokes, that's a question that has been and will continue to be debated on this and other forums ad infinitum! The performance and reliability differences are quite small and, with the E-Tec's, there is no significant noise difference either. I personally think the excess weight of the 4-strokes is a potential problem for the 18-20' hulls, especially with a bracket, since, unlike modern boats, they weren't designed for nearly that much weight. That's not so much of an issue on the 23's, which were often fitted with twin O/B's that were almost as heavy as the modern big single O/B's. Good luck with a tough decision (and convincing the wife!) I'm afraid I may not have been much help! Denny

[FishStretcher]

I sold my 1988 175 Yamaha 2 stroke, kept the controls and bought a used 2000 100hp 4 stroke for my 20 footer for a wash in price. It seems with some creative use of craigslist and the willingness to take a chance, you could get a more or less equivalent 4 stroke for only a small amount of money, if you can rig it yourself, as I did with a chainfall, or engine hoist. It did take a while for me to find one, and then sell the other, but only about 2 months. I realize you will want to keep the 225HP range +/- for a 23 footer, but it is a thought?

[eggsuckindog]

Not exactly sure I would consider a 175 for 100 and even swap regardless of stroke - just say'in

[shine]

My story: I was looking at a 2001 OX66 with about 500 hours, in great shape and perfect compression, from a dealer who would give me a limited warranty. Cost before rigging $5000

OR

2003 F225 with 360 hours, from a dealer who would give a somewhat limited warranty. Cost before rigging $7500

Judging by fuel burn numbers from others who have the OX66 combo, I figured I only had to use the F225 for about 3 years before the gas alone paid for the upgrade. Not to mention cost of oil.

Intangibles: quietness of 4 stroke while idle/slow trolling, no smell, no dealing with oil tanks, etc.

Resale: If I decied to sell my boat in 3 years, I will be able to sell it faster and probably for more than the $2500 premium I paid for the 4 stroke.

It was a no brainer for me.

Now, if I already had a 2 stroke that was running well, then no way would I buy a new 4 stroke until the 2 stroke died or needed a lot of work.

[FishStretcher]

Originally Posted by eggsuckindog

Not exactly sure I would consider a 175 for 100 and even swap regardless of stroke - just say'in

It was a 1988 175 with a bondoed cowl and it only started with starting fluid. Versus a 2000 four stroke. Sold one for $500 bought one with boat and trailer for $1000, sold boat for $500.

[Bigshrimpin]

77SceptreOB - 2.91mpg @31 mph is amazing for a 23. I'm right there with you with my 200 Merc 2.4L from 1979. No one believes I get 39mph out of her either, but the GPS doesn't lie. Run it until it dies . . . and keep quiet about your fuel burn, so you can snatch up a few spares for short money.




Fish - I'm with you on the low budget elbow grease stuff . . . but you gotta get real lucky to find any 4 stroke dead or alive for under a grand that didn't sink and seize. The gamble you take trying to save a few grand on a new 4 stroke is pretty big when you are buying a $1000 four stroke. It's pretty hard to find a "running" 4 stroke 100hp + for under 3k . . . let alone $1000.

The nice part about old 2 strokes is that you can rebuild a fuel pump for $12 in parts . . . Rebuild carbs with all new gaskets, needles and seats for about $100 in parts. Chris Carson sells some awesome fiber reeds for $125. They are simple and easy to work on (unless it's hermits OMC 225).

http://www.chriscarsonmarine.com/reed-valves.htm

Personally I'd much rather have a motor that I don't have to pay for service . . . than be at the mercy of some dealer . . . but that's a personal preference. If I had a ton of money or was older and wiser maybe my perspective would change. For now 2 spares ( and 2 powerheads, 1 mid, and 5 lowers) ready to go! 4 bolt fix . . . on and off in a few hours if I need too. Everyone's situation is different. After Destroying 2 lowers in 3 weeks on rocks in 2010 . . . I won't be changing strategy anytime soon. The season is just to short to sit around waiting for parts or mechanics that are booked 4 weeks out who refuse to work on anything older than 5 years.

[junior11]

I get 25 knots burning 11GPH with a 250 four stroke FWIW. Boat is a 23 CC with a bracket. 1972 hull.

[strick]

Originally Posted by Bigshrimpin

For now 2 spares ( and 2 powerheads, 1 mid, and 5 lowers) ready to go! 4 bolt fix . . . on and off in a few hours if I need too.

I love it