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mercury 150 is not overheating but when i flush it with a garden h mercury 150 hp. ose no water comes out the telltale

H

HTIMS57

New member
I have a 2022 Mercury 150 HP. ran all day, no overheating problems. when I flushed the engine with a garden hose like I normally do , no water would come out of the telltale It does pee when engine is running.
 
Not to hijack your forum @HTIMS57 , but I was having the same issue yesterday, same motor (I have twins) only mine are 2016. According to Mercury, it doesn't matter if the engine is in running or in tilted position, and the engine should be off. My engines pee just fine when idol and running. The only issue I could come up with is not enough water pressure to push through the upper section of the engine to come out of the telltale, which also concerns me that the engine isn't getting a full flush.
 
I have a 4 stroke EFI, 2022. The Mercury manual definitely says to start the engine during a flush-
"IMPORTANT: The engine must be run during flushing in order to open the thermostat and circulate water through the water passages"
Perhaps they changed the guidance for later models to now make running engine required.

If you're in the water, e.g. in a slip, obviously the engine needs to be trimmed up abot half way at least or you'd intake saltwater through the impellers.

Maybe HTIMS57 just needs to let the engine run for 5 minutes and then see if telltale streams.
 
I did a test yesterday- operated the boat for an hour (telltale output was fine) and then brought it into the slip. While engine was still hot I immediately trimmed it up just enough so impellers were out of water, and connected a host at half max pressure to the flush port. Per the owners manual, I started the engine. There was a lot of output at the impellers and at the prop, enough so I dont think there was risk of impellers overheating. However no telltale stream.
So now I'm wondering if there is an issue with my engine which is fairly brand new, or if the above is normal. Can anyone else with a Merc 4 stroke, year say 2020 or later, tell me if water is supposed to expel from telltale, in addition to from the impeller & prop?
thanks
 
I think this answers the OP and my own question- just noticed that the hose flush port is also used for Tell Tale output. So it's impossible on the Merc 2022 EFI engine, and probably others, to have TT when using the hose port. I checked with the Merc Corp site and they sent me an email confirming that. See diagram, the circled port is used for both flush and TT.

Screenshot_20230614_210535_Chrome.jpg
 
HTIMS57 said:
I have a 2022 Mercury 150 HP. ran all day, no overheating problems. when I flushed the engine with a garden hose like I normally do , no water would come out of the telltale It does pee when engine is running.
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did you ever figure this out? I have a 2016 with this issue. Thought it was a check valve issue, but changed that out, still no tell-tale on the flush fitting. I havent run the engine like this.
 
NCCoastal said:
did you ever figure this out? I have a 2016 with this issue. Thought it was a check valve issue, but changed that out, still no tell-tale on the flush fitting. I havent run the engine like this.
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Hi NCCoastal. We have a 2015 Mercury 150 FourStroke which did pee from the water pump indicator hole during flushing until yesterday. I get a perfectly good tell tale during running though. Did you ever figure it out?
 
Chase the telltale hole with a wire- it may be clogged. Also, this may have a poppet valve and that may be stuck.
 
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