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  Beter Mileage with Bigger Engines

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Author Topic:   Beter Mileage with Bigger Engines
Plotman posted 07-29-2004 07:57 PM ET (US)   Profile for Plotman   Send Email to Plotman  
I was perusing the performance data on the new Eastport, and I found it very interesting that at a given speed, the larger the engine, the better the fuel mileage.

I exrtapolated between the data points that Whaler gives for the 135, 150 and 200 hp Optimax engines that they tested on the boat and found that using the largest allowed power gave 24% better mpg than the smallest engine tested at a 33mph cruise.

At 33 mph
135 Opti = 3.41 mpg @ 4800 rpm
150 Opti = 3.50 mpg @4485 rpm
200 Opti = 4.22 mpg @ 3560 rpm

The difference was similar comparing a 240 Outrage with a single 225 Optimax compared to twin 150s (the twins got better mileage).

David

Clark Roberts posted 07-30-2004 07:48 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
The 200 is running at optimum cruise rpm while the 135 is running above its optimum. Run the 135 at 3500rpm and it will probably surpass the mpg figures of the 200 but you won't be running as fast, obviously. It's interesting that the wide open throttle (WOT) speeds of the 225 Merc 4 stroker are advertised, in Merc's brochure, as slightly higher than the 225 Opti. The Opti is going faster at WOT so it should use more fuel. Now, lower the speed of the Opti to same as top speed of 4 stroker and the Opti would most likely get better mpg. In my experience a larger engine running at optimum rpm will get superior economy (fuel consumption and wear and tear) to a lower hp engine running at high rpm. Happy Whalin'... Clark ... SCN
Peter posted 07-30-2004 07:59 AM ET (US)     Profile for Peter  Send Email to Peter     
Nice to see a little data backing up all the preaching to the choir we've done over the years about hanging the biggest motor the boat/transom will handle. I

nteresting that a 2800 lb boat will do 50+ mph with a 200. That Eastport must not have much deadrise at the transom. I imagine its got the same flatish stern as the Nantucket.

Plotman posted 07-30-2004 09:26 AM ET (US)     Profile for Plotman  Send Email to Plotman     
The best MPG on the 135 is 5.00 between 19-21mph. The best MPG on the 200 is 4.87 - an insignificant difference from the peak mpg of the 135, but it gets this at 30mph.
Peter posted 07-30-2004 09:46 AM ET (US)     Profile for Peter  Send Email to Peter     
Realistically, at plane, that boat will be most comfortably run between 25 and 30 MPH. As Clark noted V6 2-strokes are at their most efficient operating speed between 3000 and 4000 RPM and typically around 3500 RPM. So the 200 is the far better power choice over the 135 or 150. While it will cost more initially, it will get better economy and be quieter at cruise, and it should last longer.
Bigshot posted 07-30-2004 01:44 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Ditto to the above answers. Difference here is that we are comparing V6 to V6. Where this may be different is if you comapred the 150 opti to the Yamaha 150 4 stroke which is a 4 cyl. If economy is a factor(which should not weigh TOO heavy when difference is 1/2mpg) take a 130 Yamaha conventional 2 stroke and compare it to a 150 Yamaha V6. Economy is gonna be way different because of 4 vs 6 cyls. Top speed will suffer some but who runs at WOT all day, I am just talking at say 28mph?
LHG posted 07-30-2004 03:21 PM ET (US)     Profile for LHG    
The other thing is that the larger HP engine will last longer, due to cxonsiderably less piston travel and less general wear and tear. High RPM is the killer, making a smaller engine work harder and hotter. Always go for max power, or even then some. This has worked for me for over 35 years. And now we know economy doesn't suffer either.
kamie posted 07-30-2004 06:56 PM ET (US)     Profile for kamie  Send Email to kamie     
David,

glad to see I am not the only one doing this. I was hoping that BW would offer the 270 with a pair of 250hp Verado's but they dont list it as an option. For the 240 the twin 150's win out in everything from planing speed to milage.

george nagy posted 08-02-2004 02:21 PM ET (US)     Profile for george nagy  Send Email to george nagy     
It is interesting to see how similar the performance is between the 135 and 150 opties on the 205 eastport. It is important to note that the few mph difference isn't as important as the 3 star carb rating only available on the 135.
Plotman posted 08-02-2004 02:31 PM ET (US)     Profile for Plotman  Send Email to Plotman     
I don't think it's that surprising, George, isn't it the same engine? My Guess is that the HP difference is entirely electronic.

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