2001 Honda 50 HP overheating with steam coming out tell tale.

[CastitMan]

We bought a used 50 HP Honda outboard. We know the previous owners and it was gently used. On or second time out we hooked up a tube and were pulling kids, the engine power dropped and we limped back to the dock. We had been out for about 1/2 an hour and all was running fine. Now if I leave it idle at the dock I can start with a good stream from the tell tale that then gets less and less until it starts to spit steam again.

We had the water pump changed but it is still doing the same thing, so basically no change. I have taken the screens off the intake and all looks clean plus I am assuming the mechanic would also have checked this.

I am at a loss. Is it easy to check the water jacket for a blockage, is that even a possibility?

Could it be the thermostat? Water fills, thermostat does not open so water starts to boil and steam pushes the water out?

 

[VicS]

We bought a used 50 HP Honda outboard. We know the previous owners and it was gently used. On or second time out we hooked up a tube and were pulling kids, the engine power dropped and we limped back to the dock. We had been out for about 1/2 an hour and all was running fine. Now if I leave it idle at the dock I can start with a good stream from the tell tale that then gets less and less until it starts to spit steam again.

We had the water pump changed but it is still doing the same thing, so basically no change. I have taken the screens off the intake and all looks clean plus I am assuming the mechanic would also have checked this.

I am at a loss. Is it easy to check the water jacket for a blockage, is that even a possibility?

Could it be the thermostat? Water fills, thermostat does not open so water starts to boil and steam pushes the water out?

It could be due to blockages or restrictions

Thermostat is easily checked ( its under a cover on the top of the cylinder block) usually reliable though . More likely to get stuck open than fail shut

It should just start to open at 52 C and be fully open (3 mm) at 62 C

See Boatinfo - Honda Service Manual for BF35A, BF40A, BF45A and BF50A for service manual

 

[AngusMcDoon]

At 19 years old it's likely that there are corrosion products & salt crystals blocking the cooling galleries. To know for sure you need to get the head off. If you are paying someone to do the work it might not be economic. Overheating from corrosion & blockages is the usual way for old outboard engines to die. Unfortunately the light usage you mention doesn't help as outboards tend to be age limited rather than use limited, & 19 years is old.