Classic AquaSport
Aquasport Mechanicals - things that need a wrench, screwdriver or multimeter => Engines & engine woes => Topic started by: flounderpounder225 on September 03, 2009, 03:19:21 PM
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Ok, this should be an interesting topic, I know how opinions run on outboards... :lol: I am new to the forum, and have already got some great information from many people. My dilema is... I just purchased a 1997 245 Osprey CC in awesome condition, except for the motor. I don't know what exactly is wrong with it, the previous owner simply said it needed a new powerhead. I wasn't concerned about it, because I have 1986 Chris Craft Scorpion WA with a full bracket and a 96' Yamaha 225 2 stroke which has been a beautiful motor for 8 problem free years, still sporting 120 PSI (even) at all 6 cylinders. My plan is to swap power, however it would be easier to rebuild the johnson and skip the whole re-rigging ordeal on the Aquasport. I have differing opinions on fuel consumption.... I know the 245 Osprey is a heavy boat, and a single 225 of any brand is going to like the gas, I also know a LOT of the 245's of the mid and late 90's came with the Ocean Pro 225 from the factory. Sooo, does anyone have any actual numbers for mileage/gal per hr burn rates anything like that, that could help me make a decision? Thanks
Marc
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The difference in gas consumption between the two engines would be negligible.
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Worst case is HP/10 at WOT - 2 or 4-stroke - based on the test drives I've read and personal experience. Anything else is based on the boat - so it'll vary at cruise speed.
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Are both motors running carbs or fuel injection? Fuel injection gives 10-20% better fuel economy on the same motor. However, despite the also design differences in the Johnson and the Yammie, they will run about the same fuel economy when properly rigged if both have carbs or FI.
Let's put some things in perspective, cuz everyone talks fuel economy, but few actiually "get it." Best cruise on your boat will be about 25 MPH - that will probably be about 11-12 gallons per hour on a 2 stroke carb motor, or about 2.2 MPG. Now, let's say you go from a carb motor to a direct injected motor, and you get a big improvement of say 30% - wow - that's a lot, right? Well, your fuel flow would go from 11.5 to 8, but mileage only goes from 2.2 to 3.1. You are saving at most 2.5 gallons per hour, or about $7.50 per hour at cruise speed. So to offset the $6,000 difference in price of the 225HP motors between DI and carb, you will need to operate the motors for 800 hours to break even. Most folks never get their motors to 800 hours unless they are using them commercially.
IMHO, either motor would work fine. Pick the one that is most likely to get you home every trip and go with it. Also consider one other thing - electrical output. Some older motors used the stator to charge the battery, whereas more recent motors use a automotive-type alternator to charge. BIG difference! The stator-type system can only put out about 10 amps when everything is working right, but the alternator system puts out about 60 amps. With all the pumps, lights, electronics (radar, anyone?) and other gear on today's boats, you NEED that extra charging power. Again - apples vs. apples - no real difference if both the Johnson and the Yamaha have alternator-based charging systems.
See ya on the water!
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Carbed 225hp at 4500rpm will burn 15 to 18 gph. Been there with the flow scan on 2 different Johnsons. My 225hp Optimax burns 12 gph at 4500 but the boat is running 2 to 4 knots faster due to the different gear ratio (1.86 to 1 vs 1.75 to 1). The Optimax is also much stronger out of the hole as well. The last Johnson was a good running motor in VERY good shape. Both were 1988 models. The Optimax is a 2000 model with a fresh powerhead.
An EFI engine will show about a 10% decrease in fuel burn over a carb model.
A DFI engine will show a 20 to 40% decrease in fuel burn over a carb model.
I'll have numbers on my 1990 Yammy 225hp before the years end. I don't expect it to be much different than the Johnsons.