Re: 2002 Merc 150 2 stroke running hot
Rusty;
Two problems come to mind. 1) the pump needs replacing or 2) the relief/poppet valve is not functioning properly. Sounds like number two due to the sputtering at cold takeoff's.
I have a 2000 model 150 and it has on occasion done the same.
What happens is, the t'stats are the primary "warmup" components for idle and low speed operation. The poppet valve takes over at about 2000 RPM to push more/excess water through the system, but primarily the wall of water in the exhaust cavity.
If the poppet is leaking or staying open, it dumps a contineous flow of water through the loop, not allowing the t'stats to do their job; et., heat the motor to 143 degrees, allowing the necessary warmup. This creates a "cold start/cold takeoff" and causes the engine to bog down or sputter at attempted plane.
To check/replace the relief assembly, you will have to remove the lower cowel (remove 4 screws and separate cowel). You will also need to remove 4 wires from the trim button. Then remove the starter terminal block (3 half inch bolts) and pull back to expose the relief assembly block. Has 4 or 5 half inch bolts holding the block. Remove and inspect diaphram, water diverter and poppet seat. If parts are needed, you will have to purchase each piece separately (does not come in a kit). Find all components on the starboard side of engine.
Replace t'stats and pump along with poppet assy. and you have covered everything that can cause heating (except for restrictions that may be in water passages due to sand, grass or dirt being pulled in unaware).
Hope this helps.
