1973 25' Seacraft Seafari
 

I finally have the boat running consistently after a lot of little road bumps.
Here is a video I took today. Ran great!

https://m.youtube.com/watch?v=V-W7AI9Tp_w

Very nice, 49,000 @ 40 mph not too shabby!! A humble suggestion, use only top of the line two stroke oil. If you do those OX66s will go forever!! The really good oil, full synthetic, will keep the rings from sticking and burn much cleaner. To some it's overkill, to me it's cheap insurance (unlike my health insurance)

looking good

Thanks DonV, I'll do that.

Nate - Looks good . . . Which prop are you running? You might want to consider propping it so the engine turns 5500rpm.

Bigshrimpin-thanks. I know it's a Mirage thst was custom tuned but that all I know. What would you recommend to get to 5500?

1.81 ratio lower
4900 WOT @ 40mph probably means you are running a 17p mirage?

I would probably drop down to a Mirage 15p or an Enertia 15p that should give you the extra 400 to 500rpm. Stay away from the Rev4 if you need the extra rpms.

Good suggestion! Don't know if Yamaha sells a full synthetic 2 stroke oil, but Evinrude's XD-100 full synthetic oil, made for oil injected motors, burns very clean and has very high detergent content.

BRP claims that if you run XD-100 in an E-TEC with the computer set for reduced oiling (for XD-100 only!), the motor will not only use less oil, you'll never have to decarb the motor! However some HO models don't have the reduced oil setting, and some guys that run their motor hard leave them on the factory default TCW-3 setting but still use XD-100 for extra protection. Mine is set on the leaner XD-100 setting, and I used about 1.5 gallons of oil and 155 gallons of gas on a 700 mile trip I made circumnavigating S. Fl. a few years ago. BRP advertises 1 gallon jugs of XD-100 for $45, but my local dealer buys it in bulk and sells it for $35/gallon if you bring your own jug.

Also agree with Big on propping . . . with all needle bearings, 2 stroke motors love to rev (or "yodel" as Terry E. says!), but if you lug 'em down as you're doing with too much pitch, it increases pressure and temperature in the cylinder, which increases ring, piston, wrist pin and bearing loads, and reduces exhaust scavenging, which means more carbon deposits and ring/cylinder wear! For example, although my motor hits peak HP at 5250, and the WOT "Operating Range" is 4650-5850, BRP says the OPTIMUM rpm is 5300-5500, so I'm propped to turn about 5450 with the maximum load I ever run. Don't know if Yamaha specifies the narrower optimum rpm range, but if not, I would guess that you'd be pretty close if you propped it for at about 5500 @ WOT with the heaviest load you normally carry, or at least the top half of the recommended operating range.

Excellent price on the XD-100 in bulk, which is pretty much as top of the line as you can get for two stroke oil!! I'm a very big fan of Amsoil HP synthetic oil. I buy the "preferred customer" package each year for $25, you get a very nice discount on their products, Their HP oil is the only oil that compares equally with the XD-100 and will work on the "lean setting" on eTecs. I buy it by the case of four gallons, with shipping to my front door and tax it's $120. Now as far as automotive oil I like the Amsoil "signature series", my car requires full synthetic, I change it every 15,000 miles.

Can`t remember who did the testing, but they had every one I can think of and Amsoil was just a tiny tic below xd 100 in two or three categories

Leads me to think Amsoil makes xd 100.