300x overheating/cooling problem

[prepsdk]

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

20190421_085503.jpg

[Savage]

Need to know EXACTLY how much water pressure the garden hose has, while it is hooked up to the motor.

[prepsdk]

Need to know EXACTLY how much water pressure the garden hose has, while it is hooked up to the motor.

I will check that.
FYI the motor has been flushed with this hose after each trip for several years without any problems.

[Sebber2306]

...Is that a drainhole (marked on the pic. ), or what is it?
Waterpressure on the hose should be able to keep the engine ‘cold’ enough, if the motor has been flushed with the same hose as Martin mentioned before?

[Savage]

The hole marked is a Cooling Passage for the Lower Unit, above the passage is a strainer that can only be inspected by removing the powerhead and adapter plate. The strainer is also a restrictor and must be intact, or water pressure at Idle will be low.

[prepsdk]

Need to know EXACTLY how much water pressure the garden hose has, while it is hooked up to the motor.

Savage:

The garden hose delivers 4 gallons per minute.

Today we tested the motor in a water tank, but engine still overheats.

I found some images of what is supposed to be original 300x tuners, they have a fitting installed in the square hole. please see attached.
Could it be too much water is dumped through the square hole due to the missing fitting?

We really appreciate your great help, thank you very much.

[Savage]

You gave me the flow, not the pressure.

Possible, the fitting is a restrictor.

[Sebber2306]

Forgive me Savage, just one quick question but how do you messure the pressure?

[prepsdk]

You gave me the flow, not the pressure.

Possible, the fitting is a restrictor.

The pressure is 40 psi and it's a 1/2" garden hose.

Is the fitting/restrictor factory fitted?