Yamaha 115 CVE 2 stroke warning buzzer / overheat

[gradyk]

Here is a brief synopsis:

BACKGROUND: 1992 Yamaha CVE 2-Stroke Long Shaft, Approx. 4000 hours, Owned Since New, Run Mix Rich @ 25:1

PROBLEM:
Overheats at following rates

RPM's Alarm Buzzer Starts (in minutes)
4,800 20 minutes
5,000 3 minutes
6,100 1 minute​

TEMPERATURE READINGS:

Engine With Cooling Problem​

Head 1 139 degrees
Head 2 142 degrees
Exhaust Water 118 degrees​

Engine WithOut Cooling Problem​

Head 1 127.5 degrees
Head 2 127 degrees
Exhaust Water 110 degrees​

DIAGNOSIS:

1. R&R Water Pump (impellar) and it did nothing to resolve cooling temperature
2. R&R Pressure Relief Valve (poppit) and again did nothing to resolve overheating
3. Removed Powerhead and replaced adaptor plate
4. Removed Heads and sandblasted them
5. Cleaned water jackets
6. Cleaned and/or replaced cooling hoses

RESULT: Engine ran approx 11 degrees cooler and runs 6,100 RPM's with no alarm
COST: US$1,800. Gaskets cost around $300 and the labor is a lot...around 15hours.