300x overheating/cooling problem

[preps]

Hi,

I'm helping a friend troubleshooting his 300X with a overheating/cooling problem.

300X, serial: OT235944

Engine was flushed on the gardenhose before storing for winter with no problems at all.

First startup this spring, engine overheats and horn sound after just 60-90 sec. on the gardenhose.

Impeller changed - OK, thermostats checked - OK, poppet valve checked - OK, but still overheating and the water does not reach the thermostat housing

We removed the LU and attached the gardenhose directly to the water inlet pipe to override the waterpump being the culprit. Still overheating and the water does still not reach the thermostat housing.

But we discovered that water pours out of a hole between the two large exhaust ports (see image below), and if we put a stick against the hole and closes it, water rises to the thermostat housing immediately.

Could it be a blown seal, corrosion in the adaptor plate or ... ?

Can you help me with this problem?

Best regards
Martin

[Chaz]

While it's true that is an area that tends to burn the gasket / erode the aluminium, that square hole feeds water down the can to cool the bearing carrier in the lower unit.
It uses this hole ...



Then thru this little filter guy .. and out the bottom ..



3.0L Idle with 1 to 5 psi @ idle. Mine always seem to idle with "none" visable @ the dash. As long as the tell-tale is pissin good, then it's movin water.
They also have large diameter, low temp thermostat's. The lower (port side) opens causing enough of a leak that little to no water runs out the starboard side until 800 -1000 rpm .

Check the cyl temp senders. If they are good, put the highest resistance one in the starboard side. That goes for the one in the plenum box too , all three are the same .