2003 Yamaha 250 OX66

bulllseyee · Mar 2, 2008

Hey guys, need some advice on my OB which recently came with the 2520 I just purchased. I have two issues... First, she runs like a top at all RPM's except for the low ones when I first kick it in gear(trolling speed) . Just seems to be a little rough. It wont cut off on its own, but just is doing some sputtering and shaking a bit? Next, we just did a couple of improvements(electronics, thru hull seacock,etc...) and also dropped the lower unit and replaced the water pump impeller. While she was on dry dock, I hooked up the muffs and fired up the OB to make sure she was pumping water. Everything checked out good, however I notice the prop spinning in forward motion? More so than what Ive seen on other OBs caused by vibration or whatever. I took a piece of wood and could fairly easily get the prop to stop but as soon as I released she would start spinning again? Both are bothering me quit a bit and ANY advice or recommendation is greatly appreciated! Thanks, Clayton

TomS · Mar 2, 2008

I wouldn't worry about either problem.

I'm pretty sure the 250HP Yamahas drop a couple of cylinders at low RPM, and tend to run a little rough with the engine vibrating a bit more than you would expect.

My 200HP does the same thing while running on the muffs, I don't think its a problem.

There are a few other preventative maintenance things you should probably do, no knowing the engine's history.. otherwise these are great motors.

-- Tom

John_Madison CT · Mar 3, 2008

I agree, I wouldn't worry about either. A rough idle is typical for the Ox66. Also, I've seen the spinning prop in neutral in a lot of boats.

FWIW, Yamaha stopped making the 250hp Ox66 in 2002.

bulllseyee · Mar 3, 2008

Interesting, Its on an '03 boat...Not unheard of though. The concern I have with the spinning prop issue, is that when I come out of the slip on a flat calm day I can notice the boat slowly creeping forward in NEUTRAL! Seems dangerous to me?

TomS · Mar 3, 2008

Well that might be an entirely different problem. The prop spinning I have seen - the boat isn't in gear, and it appears to be just slowly spinning due to the water moving through the system. That is entirely different than the prop engaged and spinning while in neutral and may be an indication of a real problem that is worth checking into. Maybe the previous owner had the water pump changed and the shift rod assembly got messed up.

-- Tom

gw204 · Mar 3, 2008

What's your in-gear idle speed? If that is too low, it will cause the engine to run rough like you're describing.

The prop thing is normal. My '98 225 OX66s do it, my '02 Merc 150 did it too. Nothing to worry about.

bulllseyee · Mar 3, 2008

Idle speed is between 3 and 3.5mph. At idle she runs smooth until I kick her in gear? touch the throttle a bit and she also runs smooth. The only sputtering I get is when I just but it in gear? Motor stars shaking a bit and you can feel more vibration throughout the boat... I just put new plugs and a new water pump on the OB.

goinsfishin · Mar 5, 2008

I think he meant your in gear RPM at idle. Should be around 6-700. too low and you're doggin the engine and its trying not to stall, too high and it will grind going in gear. Not to mention that if it's too high then you'll never get down to a good slow trolling speed, 2.5 to 3 mph.