quote:Originally posted by theoldwizard:
Somthing-Fishey. Good math ! I like people who "run the numbers". Let's try a different situation.
Yamaha F225 vs Envinrude 225 Ficht
$14,000 vs $12,000 (prices from Eds)
Fuel - Maybe not the same. A 250 Ficht beat a 250 HPDI across the board on fuel economy in a head to head test in the May issue of Trailer Boats Magazine. Compared to the burn rate of an F225 (July '01 TBM) the Ficht is better up to about 3000 RPM (different boat)
Oil - not the same
For 100 hrs/800 gallons of fuel, including a fair amount of idle/trolling, my guess is about 10 gallons (or less) of oil, or $250 (synthetic) against $175 (is that assuming synthetic 4s oil ?)
Finally, I think you are way under estimating your valve adjustment cost. 24 valves could easily cost $300-400 (Yeah, they are essentially free if you do them yourself). I don't know what "the book" calls for; every 100 hrs ? every 200 hrs ?
You are correct on weight. The 2 stroke does weight less.
The simplicity of a 2 stroke (no valves, springs, cams, etc) means better reliabality to me.
Don't get me wrong. I have nothing against 4 strokes (I own a F115 Mercaha). But don't write off 2 strokes as more costly.
I think the average fuel burn between the two would be close enough to not really effect the price outcome substantially. It also matters if you want to "Cruise" at a certain speed or most effecient speed. I think 2 strokes will win the first, but 4 strokes will win the second with a corresponding hit on fuel burn. You can look at the performance reports for the Scout 280 (F225 and 250 HPDI) and the 31 Contender (F225 and 300 HPDI) the F225 gets about 15% better mileage and only cruise about 4mph slower in the Scout test.
Yamaha actually recommends against synthetic oil in a 4 stroke. When I asked them after I bought my motor, they said it has poor emulsification properties and use regular oil, but even if you use it it's only 5 qts, so $18 and $20 for the filter. You are still using $250 in 2 stroke oil.
Yes, I am underestimating the Valve adjustment, because I have yet to hear of someone needing it. At 400 hours there is a CHECK, an INSPECTION, and adjust if NECESSARY. Mechanics around here (I checked with 3 of them) have done numerous CHECKS and never need to do the adjustment. It is the same as a OHV car, they don't really wear enough to need an adjustment after 200,000 miles. that is just a 2 stroke owner scare tactic
the check is only about $300ish and about $50-$75 per cylinder for adjustment, if needed. At 400 hours, that is roughly every 4 years for the average consumer. Meanwhile a 2 stroke has burnt $1000 in 2 stroke oil and a 4 stroke has used $200 ($400 at a dealer) in oil changes.
I'm not trying to write off 2 strokes as more costly, YET
After owning one for a while, I just like to dispell some of the myths. The 4 strokes do have a higher inital cost but I don't think they cost as much to operate PERIOD. The 2 stroke guys needed something to hold on to and they grabbed that valve adjustment with a deathgrip.
William
1900CC Key West W/ 115 Yammie 4 stroke
Biggest boat that would fit in my garage!
Need Input On 4-Stroke vs. 2-Stroke Fuel Economy 
"Life's too short to own an ugly boat ..." 
