2002 OX66 stalling problem

[Snow Bird]

I get all my parts from boats.net & found this most informative forum, keep up the good work guys.
I live in the caribbean & service for outboard motors is very limited.
I have triple 250hp outboard ox66 on a 35ft wellcraft Scarab we do snorkeling tours when the Cruise ships visit. Luckily the boat can still work with 2 engines.
The problem is after running the boat at say 3500 rpm for 10 minutes one of the motors shuts down & will not restart. Will crank but will not fire & start back for sometimes 2 hours after it has shut down. Will start back in 2 hours & run at any speed even top speed perfectly & after 10 minutes shut down with out any warning & willnot start back for another hour or 2.
I thought it was a fuel problem & have changes all fuel filters including the high pressure fuel pump filter.
It seems to be something heating up. I have changed water pump impeller, both thermostats, replaced pressure control valve(is this suppose to move freely in the rubber seat? as mine rubs the seat a bit). I changed the impeller because the flow of water through the pee tube is very weak. When I put the garden hose on to the engine to flush the engine without starting there is hardly any water comming through the pee tube. When I do this with one of the other engines the pee tube squirts lots of water, something seems to be restricting the flow of water in the cooling system in the engine. I removed one powerhead to check the condition of the water passages in the head & head cover & they were in very good condition no blockage looked like new. Put the head back on with new gaskets engine started on second crank & the same broblem ran for 10 minutes & could not be started until 2 hours later. When the engine is running no alarms go off before it shuts down.
If I happen to have picked up some sand in the water intake, as our sand in the caribbean is like powder fine how do I get it flushed out.
One ore thing I forgot to say is I have a water pressure gauge on each engine & the engine that is giving this problem, when the boat moves off to get up on the plane the needle in the gauge almost goes up to the top reading for 5 seconds & flips back down half way & then gradually comes down quarter way on the gauge just about at the same reading as the other 2 engines. This is some sort of pressure build up & then releases, if you run the motor with out thermostats you get no pressure reading on this water pressure gauge but the engines still shuts down after 10 minute run.
Maybe if I fix restricted water flow problem the engine may not shut down.
Did a diagnostics check on the motor at idle all sensors are fine. Could one sensor be overheating & shutting down the engine? I have 2 other engines I can switch a couple of sensors over & if it happens with the other engine we will have the problem nailed. What are your thoughts on that as well.
As you can see I'm willing to try anything at this point in time. Look forward to hearing from you folks, if I was in the U.S I would have many options but I am in the caribbean only one dealer for yamaha & they are very busy so whatever advise I can get from you folks will be greatly appreciated.

[boats.net]

Have you tested the overheat warning to see if working? If overheats the buzzer should sound and engine reduce to 2000 rpm,s. Have you checked fuel pressure to see if dropping off after 10 minutes?

[Snow Bird]

boats.net

The buzzer is working because when I crank the motor with the kill switch lanyard by the ignition switch detached the buzzer goes off. Also the motor does not reduce to 2000 rpms it shuts right down & will not restart for over 1 hour later. I have not checked the fuel pressure, I know this can be checked at idol but can it be checked when the motor is running at say 3000 rpms before it shuts down? can the fuel pressure be checked after the engine shuts down by cranking at the time it refuses to start back? I will go & check the fuel pressure today & let you know the result.
Whats the best way to get more water to come through the pee tube, as I said before the water pressure gauge goes extremely high on the move off unlike the other motors & then gradually works it's way backto the same level as the other motors. Seems like a build up of pressure, pressure relase valve maybe? is it worth taking off the exhaust cover under the cdi? is this an area that can get blocked by sand or deposits? Loo forward to hearing from you again & thanks for the input most appreciated.

[boats.net]

We install fuel pressure gauge and monitor it while running, looking for a sudden drop in fuel pressure. Does pumping fuel primer bulb help it or make it worse? If there is blocked water passages in block or heads it can cause portions of engine to overheat but if it's not activating overheat warning may not be causing it to shut down unless it's isolated to one cylinder causing piston to sieze up. Have you checked compression?

[jb123]

you say....when the problem occurs.....you can crank...but no fire....as in no SPARK or no start up ?? or both....

when it runs...does it run correctly??

if no spark, i would look first at the 10 pin connections and replacing/ or bypassing kill switch. LUCKILY you have extras to swap out.

if you DO have spark when the issue occurs then sounds more to me like still a fuel issue.

do you have each engine with its own battery ?? or all tied together ??

[Snow Bird]

Jb 123

Yes when the motor shuts down you can crank & it never fires but there is spark at the spark plugs.Yes when it runs it runs correctly idles at the exact same rpm 600 on the digital tack as the other 2 motors.. Yesterday ran it wide open 5000 rpms & after 5 minutes it shut down went from 5000 - 0 rpm with in a second as if you turned the motor off with the key did not sputter or anything before this happened. If you run it at 3500 rpms cruising speed shutsdown after approx 10 minutes as well instantly without warning.If you crank the motor with the kill switch lanyard disconnectd the buzzer goes off, so the buzzer works, so I put it back on. If I leave it for 2 - 3 hours it may start back up instantly as if nothing is wrong & idol at same rpm as other motors.
If it is a fuel problem ? I would think it would not restart later so easily. But if there is spark at the plugs why is it not firing or starting? You can crank it during the first hour of shut down & it will not fire once . Do these motors have some kind of sensor that can shut down the motor because it is going faulty as the motor is getting up to working temperature as it warms up? I have 2 other identical engines on this boat & am willing to swap around sensors & hope the problem shows it's face on one of the other motors. I am not happy with the water flow through the pee tube as when I put on a hose with the motor tilted up it spouts 1-2 inches max. & the other 2 motors spout 12-14 inches. When the boat is running the stream is not powerful as the other 2 motors, changed the water pump impeller 2 months ago & it didn't make a difference. Water pressure gauge goes extremely high on this motor when the boat moves off for the first time for the day & then comes down to the same level or a touch above the other 2 motors
The water seems to be restricted in this motor. I have taken off one head & head cover & the water jacket was in very good condition so I did not remove the other head. The exhaust water jacket under the cdi does this sometimes get cloged with sand is it worth taking this off & checking? checked the water pressure valve in this area & replaced seat, found no sand or anything that would clog the pee tube. The overheating alarm never sounds when the engine shuts down & the overheating sign on the digital tack does not come on. I would like to see more water passing through the motor though. I have to check the fuel pressure for Boats.net & get back to them, they also wish a compression test on the cylinders.Boats.net asked if pumping fuel primer bulb helped, no not at all the bulb gets hard & when you crank the motor will not fire. I have changed all fuel filters, including the one in the highpressure pump, I now realise there is another small filter on the high pressure pump by the fuel pressure regulator, it's called Filter,comp 65L-13905-00-00 I wonder if this could be cloged & restricting the fuel, will check it tomorrow Wednesday. You asked about my batteries, they are all tied together as one as I find I get good cranking power & they are always charged, but if they run down they all run down thats the negative.I will make some more checks tomorrow Wednesday & post my results to this forum, once again thanks to all for your ideas & hopefully we will get this problem solved & out in the open for all to see.

[boats.net]

I would still check compression and fuel pressure. You might replace main relay. Also remove fuel vapor tank and clean inside tank and fuel filter, replace all fuel filters.

[Snow Bird]

boats.net & JB123

Did a Snorkeling tour today as the boat is used for snorkeling excursions & the motor shut down after running at 3500 rpms for maximum time of 5 minutes. That was at 12.55p.m & did not restart until 3.40 p.m when the boat got back to the dock I tryed to restart it several times during the day, I also primed the fuel primer bulb & no difference did not fire once until it started at 3.40p.m. Lucky thing I have 3 motors, but it is very hard on the motors when only 2 are running. I did not do the compression test today as I did not have the instrument but it will be done Thursday morning. Checked the fuel pressure on the hose valve that comes off the fuel vapor tank it read 35 P.S.I at 700 rpm when idling at the marina before going out this was the exact same reading as the other motor I checked. Changed the filter last week in the fuel vapor tank, checked the condition of this filter this morning & it is like new & there is no sedement in the vapor tank it is extremely clean. There is a pump in the vapor tank, I was wondering if this pump could be working on & off or the wire that feeds power to this pump is not being energized at times. Is there a way that I can check if this pump is getting power after the motor shuts down?? If this pump is not getting power the motor is going to shut down instantly, this pump is fed by 12 volts?? can I put a tester on it to see if it's getting power when the motor won't start?
If it's getting power & won't start do you think it would make sense to swap over to one of the other motors the complete fuel vapor tank? where does the power to feed this pump come from, a relay that could be breaking down?
You asked about fuel filters, the one on the motor was changed 3 months ago I will change it again & the one in the vapor tank was changed last week both were replaced with new filters. Before these are Racor fuel & water seperators these were changed 8 months ago, I will change these tomorrow.
Now the main Relay you ask about should I swap this over from another motor or replace is this relay part # 61A-81950-00-00 the motor that is giving the problem is model SX250TURA. Replaced thermostats in motor today had 2 new ones in my spares. Still not much water comming through the pee tube on the side of motor when flushing motor with garden hose at marina afterwards. Even when motor running during it's first 5-10 minutes at 4000 rpms before it shuts down not near as much water pressure as the other 2 motors but it must be getting enough water as the overheating buzzer doesn't go off.
I think I am ready to swap parts between these motors after I change the fuel filters & do the compression test. Took out the spark plugs this morning & they are light grey not oily all looked the same this motor is doing 600 hours.Anymore suggestions guys, ready to try anything the other motors have never given a days problem.

[jb123]

the motor still TURNS when it stops running so comp SHOULDNT be an issue, YES??

you need to leave the gauge ON and see what the reading is when it shuts down or run it at the dock , watch and look for the change.

I assume your boat is in salt full-time and more likely to have corrosion issues than others?

[Snow Bird]

Jb 123

Yes the motor turns like normal after it shuts down, but won't fire up or re-start. I will try it with the gauge on & see if it changes, but it gives no warning just shuts down with in a second, I will monitor the gauge before it shuts down to see if there is any change in reading. Yes the boat is kept in salt water but the engines are flushed with fresh water by hose when they are in the full up tilt position after any day they have been used.

[Snow Bird]

boats.net & jb 123

Ok guys I think we are getting close to solving this problem. The motor ran again today for 5-10 minutes at 3500 rpms & shut down. When we got back to the marina I did a fuel pressure check on one of the motors (fuel vapor tank) that works well. First I released the fuel pressure at the valve it read 0 psi I then turned on the ignition switch without cranking the motor & it went up to 35 psi, I started the motor & it stayed at 35 psi at idle.
I then tested the fuel pressure on the next engine this is the one that would not restart (the trouble motor) I checked the fuel pressure & it read 0 PSI I then switched on the ignition switch without cranking motor & it read 0 PSI I cranked this motor & the reading was also 0 PSI. It would not start.
I then checked the voltage going to the pump of both fuel vapor tanks on both engines. With the ignition switchs in the on position but engines not fired up, the engine that works well had 12-13 volts going to the fuel vapor tank pump & the engine that has the problem was reading 0 volts.
So we are getting close to solving this problem.
My next question, where does the power come from to run the fuel vapor tank pump? Does it come from a relay that is faulty & working intermittent, or a faulty sensor or I hope it's not the CDI unit. I restarted the problem motor after 2 hours & it started when it got back power to the pump & thus got fuel. Look forward to hearing from you guys on what you think needs to be replaced. Thanks for your help. Not sure what I would have done without this forum.

[boats.net]

The red wire should have 12 volts with key on and it does get it's power from main relay. The CDI controls the ground to activate fuel pump.

[Snow Bird]

boats.net

I have called boats.net to order this main relay, I do not know the part number they are to look up the part number & get back to me. If you know the number I can give it to them, I will replace this part & see if it does the job. If it doesn't solve the shut down problem I guess it will be the CDI unit. I will keep you posted, thanks for your help.

[Snow Bird]

Just got a call from boats.net & they say the main relay part number is 65L-81950-01-00 what good service they called me back in less than an hour. I am going to purchase this relay part & give it a try & let the forum know the result.

[jb123]

why dont you borrow it from another motor to diagnose ?