2000 15 HP Mercury 4 stroke spitting water

[benhull]

I don't use my boat enough but have done regular maintenance on both upper and lower oil units and kept the fuel lines,carbs and tank maintained ect..... for the past 3 years that I have owned it. I only use it about 4 -6 times a year when on vacation. As I was out on the lake the other weekend, I noticed it started spitting water and a bit of steam out of the exhaust port at the rear of the upper housing. What would cause this problem?? a bad head gasket or might there be another seal or plugged port that I need to look at?

 

[benhull]

This is a picture of what it is doing.

 

[Texasmark]

I don't have a 4 stroke but on 2 strokers that is the "exhaust relief" port. It allows exhaust gasses a low resistance path to escape when the prop exhaust is submerged. So, to have water exit is normal. However Steam means your internal water temp is excessive. Your tell tale stream seems to be reasonable. I notice that you are in a barrel. Did you check the temperature of the water in the barrel? Going to bet your water is extremely hot and when added to the engine heat removed may be adequate to cause you to generate steam.

When I ran in a barrel for any length of time I kept the hose in the barrel keeping fresh/cool water for the engine's water pump to pickup and feed to the block.

Next thing is once you get that looked at, it wouldn't hurt to change your impeller in your water pump and your thermostat. Sitting for long periods are bad on the rubber impeller as it takes a "set" and in the eccentric operation of the pump, when the blades are supposed to expand to follow the expansion part of the eccentric, they can't and you loose water pressure as a result.b

If you don't have a manual on how to do that, iboats sells parts and manuals/access to manuals. Check Boat Parts and Accessories above for both.

Come back with how things are going/went.

 

[benhull]

Thank You Ill change the impeller and thermostat because I think it is well over due anyway. the water from the tell tale seems good and strong. But it did it on the lake also when in cold water so the temp in the barrel isn't an issue. The spark plugs seem ok.( No signs of water in the chamber). ​I am just afraid of doing harm to the motor if I run it a lot and water is getting in someplace its not supposed to be. I don't recall it spitting water from this exhaust port before. It does spit more steam and water when I slow the engine down from mid speed to idle.

 

[Texasmark]

Thank You Ill change the impeller and thermostat because I think it is well over due anyway. the water from the tell tale seems good and strong. But it did it on the lake also when in cold water so the temp in the barrel isn't an issue. The spark plugs seem ok.( No signs of water in the chamber). ​I am just afraid of doing harm to the motor if I run it a lot and water is getting in someplace its not supposed to be. I don't recall it spitting water from this exhaust port before. It does spit more steam and water when I slow the engine down from mid speed to idle.

That last sentence smells of impeller change time. While you are at it good time to change your lower unit gear oil. Wall mart has it in the quart with a connector, hose and pump. Makes it really easy to change.....in the sporting goods dept.