At my wits end - Need help - Mariner 15hp (2003) steam tell tale

[Anser]

Hi All,

What a great forum !! I have just joined and would like to say hi ...........

Im having a problem with my 2003 mariner 2 stroke 15hp outboard. Had some leaky gearbox seals when I bought it which have been replaced. Along with the pump seals, Impeller , Water pipe top seal (power head) she runs like a dream but constantly only spits steam out of the tell tale what ever I do. She used to have normal flow

There is flow from the thermostat housing all the way to the bottom of the water pipe so no blockages and the thermo stat is obviously opening. I have dropped it in a cup of hot water to make sure it is moving.

I have tested the lower unit (pump) in the water to make sure it is pumping and it is.

I have this all on video if anyone would like me to email it to them

I'm out of ideas !!

has anyone else ever had this problem with this type of engine and if so what was the resolution ?

Thanks In advance !!

 

[gm280]

Well first things first Anser, :welcome: to iboats.

I realize you stated you have clear tube back to the pump and that you also tested the thermostat and it works. However, have you actually flowed water the opposite way to the tale tell pee tube? Not sure about where you live, but where I live dirt dodders love to built their nest in the output tubes. And there are so many insects that will crawl in there and stop up a passage. So check to see if the entire water system is clear. And are you certain when you installed the new water pump impellor you installed the keyway in the driveshaft to the rubber impellor to make it pump? JMHO!

 

[flyingscott]

At what temp did the thermostat open should be 120 deg for that motor. The 143 deg thermostat looks exactly the same and will cause that to happen.

 

[Texasmark]

At what temp did the thermostat open should be 120 deg for that motor. The 143 deg thermostat looks exactly the same and will cause that to happen.

Gee I'd like to know the mechanism on that. Obviously you have BTDT. Part of my curiosity is that you don't get steam on the larger engines using the 143, like my 90 and son's 150. Maybe it's not a stat temp per se but the cooling capacity of that particular engine model may not have much if any reserve and with the 120 it has time to get the stat open before it gets to steaming temp whereas the 143 is so close that the block comes up to steam temp before the water gets to circulating good which means to me that the engine runs hot all the time......Yes? No?

 

[flyingscott]

Call merc with that question they spec a 120 thermostat for the 15.

 

[flyingscott]

You need to make sure the thermostat is opening at the right time. On that motor the thermostat directly controls the peehole. To double check take the thermostat out out and run it if you have a strong tell tale stream its the thermostat. If you don't it's the water pump or related.

 

[Texasmark]

You need to make sure the thermostat is opening at the right time. On that motor the thermostat directly controls the peehole. To double check take the thermostat out out and run it if you have a strong tell tale stream its the thermostat. If you don't it's the water pump or related.

That means you don't get pee till the stat opens like on my son's 150. So pee volume could be a stat condition checker as long as the engine runs long enough to get the water in the block up to temp and can hold it there with the stat open.

I just re-read the initial post. I smell stat problems. The testing in the cup of water may not have been adequate to diagnose the problem. Maybe the stat opens slightly and lets the steaming water out but not open enough to cool down the block, hence steam.

Water boils at 212F at sea level and the OT alarm is set for 195 +/- 5 on the larger engines. Remembering the process of boiling water on the stove, steam starts rising from the water long before the bubbles form and it starts a 212 rolling boil. Could be that he either doesn't have an OT alarm or it's not working or he is just under the 195 and it doesn't short out and activate the alarm.

I wouldn't run very long with the stat out as on most engines that I have seen the stat is not at the top of the block and if the stat mounting hole is large enough the block may not fill with water allowing the top of #1 to be out of the cooling water.