2000 225HP OX66

[SKMNO]

Well guys (and gals) I apologize if this is a redundant question, but have looked for similar symptoms and answers in the forum and came up short.

Motor WAS running erratic at mid-speed and it sounded from symptoms like O2 sensor. Hade all that fixed a couple weeks ago by service center, relatively inexpensively, and that for sure fixed the surging problem. Thought I used the Sea-Foam more or less consistantly but the motor sure had some definite carbon problems when they got into the O2 sensor.

NOW I have noticed at top-end speeds (about 5200 RPM w 27 prop) it just shuts down in the middle of a run, drops me back in the hole, and then kicks off better than ever. In other words it goes from running near top-end, to zero power (but never dies), sputters again and takes back off for a couple miles.

I do not run the motor at top end much as I am not into great speed and am happy to plug along at 50 MPH. It seems like it would run forever at 4500 RPM, but when I get it up near top end for a couple minutes it just shuts down, regroups and takes back off real strong.

Obviously I have a problem, and would be interested in any of your suggestions or experiences.

Seems like a fuel supply problem to me and I have read on the board about the a high pressure pump which sounds like it may be a possibility. ??

A couple years ago I replaced all the fuel pumps as I had blown a diaphraghm. This does not seem to be a similar problem. Symptoms are not the same and am not smoking as much so I don't think the fuel pump(s) are the problem.

In any case if you could offer me some sugestions or point me to a thread about this I would be most appreciateive.

Thanks - JLB

[AlabamaDale]

Sounds like the fuel pumps. I would change them along with a new fuel filter. I hope this helps..

[HawkDriver]

If it shuts down like you say it sounds like it may be a problem with the engine protection circuitry (overheat / low oil sensors) sending a false signal to pull the engine back. Do a fuel pressure check and if it is O.K. it can only be one of 2 things, a computer or spark problem.

[suncoug]

This sounds like a typical VST filter problem.

[SKMNO]

Hey guys thanks a bunch for the input.

To TR21 in AL, I really do not think the fuel pumps are the problem for the following reasons: Checked the "back side" of fuel lines and the 2 we checked were dry. One in the middle takes more time and effort to check and we never did so as just did a quick and dirty diagnosis on the 2 out of 3 we could get to quick. HOWEVER I definitely had some blown diaphragms a couple years ago and the symptoms though Similar are not the same.

Differences: When I blew a fuel diaphragm the thing smoked really bad after restarting. Plus when it shut down it absolutely shut down and stopped. Had to let it set a few minutes b4 it woiuld restart. (This is not happening now, it never actually dies but comes real close to it, then takes off like a bat out of hell.) Plus when my fuel pumps went south they got progressively and noticibly worse. This does not seem to be happening.

In fact today I ran about 20 miles total with no "shut downs". BUT I kept the RPMs below 5000. I know from experience with the problem if I get it up to 5200 RPM or above it will just SHUT DOWN after about 1-2 miles running.

To HawkDriver and SunCoug: These theories all sound like distinct possibilities. I will be the first to admit I am not an engine person. I try to take care of them and struggle to understand what my GearHead brothers take for granted.

I have read about the VST filter problem. How much is involved in fixing this?? Would the protection circuitry problem show up on a computer diagnosis which was supposedly recently done?

My local (certified Yammi) mechanic was leaning toward the high pressure pump itself. He is a great guy but we are pretty rural and I am not sure he has the exposure or solution to the probs I am having.

I thank all of you in advance for any brain cells you migh burn and suggestions you could offer.

Whoever hits the winning number (solution) to my problem wins an all day guided trip chasing bass on Table Rock Lake and we can drive around at over 50 MPH without shutting down.

Actually I'd take the 2'nd runner up or any of y'all fishing whenever you want! Good folks on this board.

Thanks again - SKMO (Shell Knob MO)

[AlabamaDale]

I hope your problems will be a easy fix. My friend had the same symptoms and the fuel pumps fixed his but i'm sure there could be other things that would cause it to act the same. Hope you get it fixed soon..

[SKMNO]

Well I did the fuel pumps a couple years ago (not to say they could not be causing problems again)

Plus just did the o2 sensor.

Anyway the thing starts and runs great (again today) as long as I don't wind it above 5200 RPM

[suncoug]

It sounds like there is not enough fuel supply for the fuel rail. Again, I would check the VST filter. It probably is easiest if you losen thee bolts that mount the VST tank and losen four bolts that are on the fuel rail.

Once of the unit of the outboard, you need to losen a dozen small screws. Make sure that you have a quality philips screw driver that fits perfectly or you might round them. Then, the bottom potion of the VST tank should fall and you can get the VST filter out for inspection/cleaning.

I would get a factory or other third party manual before you start taking things apart. It is pretty simple but it is somewhat tricky to re-mount the VST filter back on. Also, don't forget to de-pressurize the fuel VST tank and drain the fuel from the tank to avoid gas spill or risking fire.

[GlennB]

Just a thought but could your tach be off and you are actually hitting the rev limiter?

[Bada$$Bullet]

I know this probably isn't your problem, but this was mine:

I was running at WOT a few times and it would shut down. For a few trips I could not figure it out until one day I saw water draining out of the controls hole in the front of the motor. When I got home I ran the motor on the cones with the cowl off. I noticed a 1/4" scew was loose (in the block) behind the powerpack and it was spraying water on my plugs and other wiring. I dropped the power pack and tightened the screw. I have never had the problem since.

Just for your information.....you may want to check that.

Good luck.

[Tamale]

I have the same problems as this guy.

I changed out the fuel, fuel filter, fuel pump assembly's, plugs, and primer bulb. My boat just cuts out. This usally occurs after I've ran it awhile pretty hard. When its cutting out I can mash on the gas and it will go thru and run like great.

Any ideas?

IS there a pic of the VST tank anywhere?

[Rich Z]

Suncoug +1!! VST filter clogged up! The VST is the same as on a merc. Merc has a bigger filter with more surface for gas to flow through, will last longer and will work on Yam. The pump is also the same. Good luck on trying to get just the new filter. It’s best to clean with carb cleaner and blow it out with air.
The typical symptom of clogged VST filter is described in previous posts. Motor will run up to higher rpm or wot and bug down to idle. Fuel is burned off too quickly in the fuel rail and the fuel pump is starving for fuel but will pick up enough fuel at idle to fill/pressurize the rail so you can make another short run. It’s also best not to run the motor under lean condition unless you have a fat wallet.