2520 xl, 250 OX66 Performance Numbers

[Megabyte]

Do folks feel the bigger trim tabs make a big difference in efficiency (low speed plane)?

Absolutely.

Experience here has shown that 24x9's are what the 2520 seems to like, although I know of at least one member who installed 30's.
My boat will stay on plane as low as 9kts if required by sea conditions.

Use the search tool and you'll find lots of projects where owners have upgraded their tabs.

With the addition of a flowmeter, you'll be able to instantly see your burn rate as you change speed and trim. It's a valuable tool.
Since the flowmeter registers the rate and amount of fuel used, you always know how much fuel is in your tank
I have an alarm set on mine so when I reach 20 gallons remaining, it lets me know to start thinking about heading to the fuel dock. 8)

 

[Brent]

nope, Mb always has a good picture

Any pictures of the infamous "winky blinkly" light and how to make one?

 

[DaleH]

I have a 2520 DV and a 250hp Ox66 on a bracket.

I seem to get very good #'s compared to what I'm reading. With half a load of fuel, I can easily get 25mph at 4500RPM's. Often it's better. The fuel burn is about 14gph.

I try to stay under 4500RPM's a little, such as 4300 if I can as the economy increases and the speed decreases only a little. I never get as bad as 1MPG, evern fully loaded in heavy seas. The worst I've seen is 1.2MPG and I often get 1.8MPG.

A few years ago I did a long offshore trip where I averaged 1.7MPG, fully loaded, calm seas. I'm running a Mercury Mirage 17P 3 bladed prop. and get 5300RPM's WOT trimmed out.

FWIW a friend has that same motor ands prop on a fully rigged 2530 model and only turns 5100 RPMs, which for years I have been telling him is too low. And he'll do long trips fully laden with fuel and offshore gear. He says he's seen 2mpg in flat seas though. But his boat also wears TOO DARN SMALL Lenco tabs and he's yet to upgrade to larger ones.

 

[DaleH]

BTW, attached are instructions for cleaning the O2 sensors in Yam OB motors.

 

[SBH2OMan]

And here is the $53.00 O2 sensor that can apparently be used to replace the $300 Yamaha one by splicing the connector off the old one:
http://www.autozone.com/autozone/parts/ ... 63003_0_0_

Bosch 15703

According to postings on THT and Yamaha forums on iboats, you have to modify the housing to make it fit, and a "heat sock" from a spark plug is a good idea to protect the modified housing from the larger stem that heats up, but once you do, then you can change out the Oxygen sensor as part of annual service - for me spending $53 is "cheaper" than spending two hours fiddling with carb cleaner and testing the old one, which I am sick of doing. This modification is on my list of things to do over the coming winter.

 

[stonebuster]

Looking for some info on anyone running a similar setup.
I bought the boat this season, and expected much better performance.
The engine seems to work very hard to push the boat, and I have to run the engine @ 46-4700 RPM for a 18-21 knt cruise, depending on conditions and load. I don't have a flow meter, but I'm burning a ton of fuel at this RPM.
I expected this to be a fairly efficient (for a 2 stroke) set up at an easy cruise - say 41-4200 RPM, but that only pushes the boat at @15 knts in calm seas. The boat has the original factory tabs.

Any feedback would be very much appreciated.

I have an XL w/225F 41-4200 @ 18kt. 45-4600 @ 22-24kt. Wide open 55-5600 33knots. My fuel burn is about 2mpg or slightly better in normal conditions. The XL's are @ 5600# dry weight (heavier than DV) so you can't really compare numbers. I would expect you to get 2mpg or close to it at cruise. How many rpms are you turning wide open? That could indicate a improper prop issue. I know mine's a 4 stroke and you're a two but we've got the same hull. Good luck.