Yamaha Outboard 2002 VX200TLRA overheat

[linhcraig]

My outboard keeps overheating. It idles fine but shuts off after a couple minutes on plane. I found a broken bypass cover on the pvr and replaced the grommet, spring, pressure control and bypass cover. That didn't solve my problem. I then replace the thermostats. That didn't work either. Am I missing something? Please, I need some help. Got to get back at the Cobia.

[99yam40]

overheat should not shut off motor, it should set off an alarm buzzer and reduce the RPMs to about 2K
unless it is locking it up by seizing the pistons to the cylinders

[linhcraig]

Sorry, it shut off before I fixed the bypass cover and spring. Now it goes down to idle

[99yam40]

well the 1st thing I would look at or replace when overheating would be the water pump with plate and cup, since you have replaced all the other components already if water pump does not help and you are sure it is overheating then it looks like you may have to clean the water passages

[Tucker]

X2 on 99yam with replacing the pump. Then run it a tub with salt away.

[linhcraig]

I pulled the lower unit and checked the impeller, looks perfect . Motor pee and the flow increases when the motor rev up.

[rodbolt17]

then you definatly have an issue with the pump or the passage to the power head OR you still dont have the pressure control valve correct.
still should NOT shut off NOR go to idle speed when the alarm triggers.

[linhcraig]

It is definitely not an overheat problem. What would cause the motor to shut off automatically. I get to plane and am running 4200 rpms and after a minute it shuts off completely. I replaced the gas filter on the motor and the canister filter by the tank.

[rodbolt17]

the only alarm you may get thats associated with engine shutdown is low battery.
at about 10.5V the alarm triggers, at about 9.5V the fuel pump,main relay and injectors drop out.
other than that, there are NO alarms involved with engine shutdownçdid you check the filter inside the VST.
did you carefully remove and test the low pressure pumps.
running the fuel rail low on pressure can shut it down violently.
no alarms associated with rail pressure but the shut down can be just like you switched the key.

[linhcraig]

i'm not getting an alarm when it shuts down. what is the fuel rail pressure? It does shut off like you are turning the key. Is the fuel rail pressure something I should get a mechanic to check out?

[rodbolt17]

its your motor do as you wish.
either have the system tested at the failure load and RPM or risk a piston or worse.
or buy the test equipment and do some reading on closed loop speed density EFI systems.
its basically the same setup that the automotive industry has used since the mid 80s,
80s.
aint but so many ways to make a speed density EFI setup.
its incredibly simple but certain paremeters MUST be met or the air-fuel ratio goes outside the limits of sustainable combustion and the engine shuts down.
sometimes quite rapidly.
its amazing how narrow the air to fuel ratio is on gasoline internal combustion articulated rod engines.
go to lean,much below about 12.5 to 1 and the combustion becomes quite hot and uncon*****able and bad things start happing,go lean enough fast enough and it simply quits.
to rich,much above about 15.5-1, and it cannot burn properly and starts leaving excessive carbon and the flame continures to burn down stream in the exhaust where its not supposed to nor are the ex components cabable of the extra heat, and bad things happen.
thats the whole point of speed-density closed loop EFI.
map sensor gives baro reading at key on to the ECU on OX66.
intake air temp gives air temp readings to the ECU.
the ECU now knows the DENSITY of the air,how much oxygen is avalible per cubic centimeter or liter or cubic inch,depending on the ecu but you get my drift.
now we toss in the engine coolent temp.
this gives the ECU an idea of what temp the block and heads,thus the combustion chamber is.
remember a cold engine requires a richer fuel mix for the same amount of air.
this is also why NEVER run an EFI without the t-stats.
now we toss in the crank position sensor and the pulser coils.
now the engine know the crankshaft position in relation to the pulser coils and TDC.
based on these two inputs the ECU now knows engine SPEED.
hence speed density EFI.
now we toss in the throttle position sensor.
this gives the ECU throttle angle information, how much air are we allowing into the intake.
now the ECU makes some quick calculations,about 32 times per second, looks at the density of the air,the amount of air allowed in and comes up with a calculated ign timing and injector on time to make the engine speed match the ECU internal map.
running closed loop,O2 sensor input valid, the ECU is looking at the amount of UNBURNED oxygen in the exhaust and trims(modifies the basic map) the injector on time trying to maintain a 14.7-1 a-f mixture.
the knock sensor,if knocking due to detonation, can modify ign timing,retard it, and add fuel by modifying the pulse width of the injectors.
the absolute most critical part of the system is fuel rail pressure.
its also the only part not monitored.
see how simple this is.
its all about the 14.7-1 A-F mix.

[linhcraig]

A simple yes would suffice.lol

[rodbolt17]

why a simple yes when your bored behind a keyboard