both ox66 power down with buzzer. resets buzzer in nuetral

[Kingfish999]

my parents boat started having an issue. it has dual 250hp ox66. when cruising both engines will randomly suddenly power down at same time but still run similar to overheat. the warning buzzer will sound (it only works for port engine). the buzzer will keep going and the engines will be unable to power back up over ~2k rpm until you put the engine into neutral. soon as you put in neutral, the buzzer will stop and you can go again.

unsure what would cause this and it pretty random. over about a 20 minute test run at different rpms, it did it about 5 times. sometimes go few miles in between, sometimes less than half mile

my first thought was overheat but never had both engines do it at the tame time, every time. and the buzzer only stops when putting it in nuetral? the engines no longer have the oil system, we premix it, and those sensors have been bypassed for years.

i have aftermarket digital gauges that dont really work correctly and i been working with the designer to work out the kinks. my temp gauges are very unreliable but do occasionally show actual temps but usually are far off, but i think it MAY have gotten up to 190* occasionally on one engine. the water pressure show 19psi on one and 9psi on the other when cruising, recently replaced waterpump on one engine is reason for such a difference. have good fuel pressure

[boscoe99]

With twins if one motor has a fault then both motors will go into RPM reduction mode. To keep someone from motoring about with one good motor and one bad motor.

There are two buzzers behind the switch pane. If the left buzzer is sounding then I would presume that the left motor is the one having the problem. Does the right buzzer work or not?

To reset the system the key for the faulty motor needs to be turned to the off position.

Since some fool removed the oil injection system my guess would be that the left hand motor is having an excessively high temperature.

[Kingfish999]

took it out again tonight and does seem to be overheating issue but on the starboard engine. the port engine has the working buzzer.

we planed the boat out on each engine individually for a while and the port seemed to run. the starboard did overheat doing so. coming back in we even ran the port full power with the starboard half power and still eventually powered down

the starboard engine has 19psi cruising so im assuming issue with thermostat despite them not being very old. might also plan on doing waterpump in the other engine soon to restore pressure, its probably time.


honestly im just happy i dont have to replace a lower unit or rehub prop again. my parents were convinced it was a spun prop and had already swapped the spares on. when i looked at the hub it looked fine and how they described the issues sounded like it might have blown the lower. i swapped the good props back on and they were fine. they must have just heard the dog clutch from decelerating too fast or something

the oil system cost us a couple powerheads and a few headaches but thats another story. and my dad is oldschool and has been pretty happy with premixing since he fill it 50gal at a time. our 115hp we still have the oil injection in it.

[99yam40]

how did the oil system cost some powerheads?
as long as you take care of the oil system and alarms, I do not see how it would cause any problems.

if you do not take care of anything it tends to not end up well

[Kingfish999]

IIRC, the small mechanical oil pump on the engine had an issue that it would stop pumping oil. unsure of why. caused power head to throw a rod and split the block. bought a reman powerhead and during break-in it seized up. luckily it did not throw a rod so i was able to rebuild the block tho it did need 2 cylidners sleeved. when adjusting the oil pump arm and bleeding it, it seemed to pump fine but had some issue that would make it not pump randomly. they also had a powerhead failure due to a bad oil level sender on the engine. ultimately parents decided it was not worth risking another powerhead so they went the premix route. its not my boat or my money.


my dad pulled the thermostats today. found one of them defective. it was opening up but the rubber the poppet seals against was pealing away and coming up with the poppet not letting any water through

[99yam40]

OK , the pumps are gear driven off of the crank, so when the crank turns the pump operates.
crud building up inside the tanks could be a problem, but draining and cleaning them is part of the maintenance.
there are screens and filters to clean or replace as needed ,and sumps to drain.
also there are check valves to keep the oil from draining when they should not be.
keeping the oil tanks clean and free of water/condensate is important.

stats and poppits are also something that needs regular maintenance along with the water pumps.
also keeping the gauges and alarms in good working order is very important to alert to a problem before it damages a motor.

[Kingfish999]

stats, waterpump, relief are only few months old on this engine. just a defective stat. other engine is due

original gauges were trashed due to being faded and lightning strikes. currently running a setup a friend is developing thats twin 10" touchscreen displays.we are still working out the kinks, once perfected it will be awesome. should be able to read 3 fuel tanks (two using 0-5v aircraft capacitance senders), o2 sensor volts, tps volts, fuel pressure, water pressure, temps, tachs, direction, speed, and have alarms for fuel/water separators. also still changing the layout of the displays

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