Nimrod18
Well-Known Member
Today I started my Mariner 6Hp 2 stroke for the first time. The motor came with my trailer sailer but, in the 4 years I've had the boat, I've never used the motor (Rutland is electrics-only for us sailors).
I did my due diligence on the fuel tank, filter, impeller and gearbox oil. The carb and thermostat I took on risk.
In a bucket of water, she started today on the second pull and ran sweetly, with plenty of cooling water, lovely tick over and smooth response across the rev range. However, the cylinder head covers (and rest of engine) didn't get beyond lukewarm. What's more, if I increased revs, the covers actually cooled down to almost chilly and stayed there. I figured that the thermostat might be stuck open, so I took the cover off to reveal what you'll see in the photos.
The thermostat is firmly wedged open and won't budge.
There doesn't appear to be a spring.
Around the top of the thermostat is a deformed piece of plastic, that appears to have partially melted and started to flow in the direction of the water channel. In fact, it had moulded to the shape of the channel and it took a bit of "persuading" to come out.
So august YBW collective, my questions three:
What on earth is the deformed piece of plastic?
If it's part of the design of "old" thermostats, what will have caused it to deform?
Anyone know if I can replace it with a "modern" one?
Herewith the details of the motor:
6Hp 2 stroke, long leg.
Labelled as Mariner. However, the serial number corresponds to a 1980 Yamaha (a bit of research on Brunswick suggests that Yamaha took over Mariner that year, though I've not validated that fact).
Serial plate says: 6ML (top row) 6H6 L 306325 (bottom row).
Grateful in advance for your assistance.
I did my due diligence on the fuel tank, filter, impeller and gearbox oil. The carb and thermostat I took on risk.
In a bucket of water, she started today on the second pull and ran sweetly, with plenty of cooling water, lovely tick over and smooth response across the rev range. However, the cylinder head covers (and rest of engine) didn't get beyond lukewarm. What's more, if I increased revs, the covers actually cooled down to almost chilly and stayed there. I figured that the thermostat might be stuck open, so I took the cover off to reveal what you'll see in the photos.
The thermostat is firmly wedged open and won't budge.
There doesn't appear to be a spring.
Around the top of the thermostat is a deformed piece of plastic, that appears to have partially melted and started to flow in the direction of the water channel. In fact, it had moulded to the shape of the channel and it took a bit of "persuading" to come out.
So august YBW collective, my questions three:
What on earth is the deformed piece of plastic?
If it's part of the design of "old" thermostats, what will have caused it to deform?
Anyone know if I can replace it with a "modern" one?
Herewith the details of the motor:
6Hp 2 stroke, long leg.
Labelled as Mariner. However, the serial number corresponds to a 1980 Yamaha (a bit of research on Brunswick suggests that Yamaha took over Mariner that year, though I've not validated that fact).
Serial plate says: 6ML (top row) 6H6 L 306325 (bottom row).
Grateful in advance for your assistance.
