Outboard Tell-tale Help

Hey guys,
I’ve got a few questions about some water cooling issues I’ve been seeing with my motor. It’s a 20 year old Mercury 2-stroke, and recently I’ve noticed that water is shooting out of the exhaust port (pic attached) - is this an issue, or is the part of the normal cooling process that I somehow haven’t noticed before?

Secondly, my tell-tale stream diminishes to almost nothing when I rev the engine to get on plane, and once I’m finally on plane it returns to “normal”. Any thoughts here? Wondering if I have a poppet valve issue.


I believe you gots bigger problems than a thermostat there. I suggest you do a compression check on the "rusty" side.

The ENTER-NET Fisherman
I believe you gots bigger problems than a thermostat there. I suggest you do a compression check on the "rusty" side.

The ENTER-NET FishermanOriginally posted by mdaddy
Glad he’s gettin good at removing bolts,might need to remove a few more.
Ok I had time to do a compression test tonight, and every cylinder had basically the exact same reading: ~130psi with throttle valves closed, and ~135psi with throttle valves wide open. I bought a cheapo gauge, so the values might be slightly off, but at least they're all consistent.

However, I noticed oil around the spark plug holes, and the spark plugs look a little fouled to me, but I could use some help interpreting them. They're all 1 year old.

Still trying to track down the source of corrosion on these bolts, seems less like a blown head gasket now...
I'd change the plugs. You are running rich, but that could just be from extended idle? I've always read plugs after a hard run. Many charts online to compare yours to. As to the corrosion on one side, I'd guess a little leakage around the hose. Only takes a little salt water sitting to cause that kind of rust/ corrosion. Not always, but I mostly remove my cowl and spray it down during an after use flush. I spray everything with oil. I've had some on here say that is not good for it, but I've been doing it for 30 years with no ill effects. I'll at times even spray STP son of a gun over everything under the cowling.

Remember on the charts that you are running an oil burning 2 stroke. You don't want em looking a little tan. I'd rather see them darker than it running too lean.

Haven't heard from Chris lately?
Last edited by Fred67
You got good compression. Odd that one bank is rusted on the outside and the other isn't.
Grounding on port bank? Leaking hose at thermostat port?
Port side got hot at one time??? Engine sat in salt water for extended time???

Too many things to chase on a twenty year old motor. Change the thermostats and run it.
Clean off corrosion on the electrical connections and spray electrical grade silicone on it and invest in towing plan.

The ENTER-NET Fisherman