Engine not peeing good and overheating with new thermostats

2005 Merc 150 2 stroke carbed

So last time I was on here I was hoping you guys were right, and letting the temp get past 143 would open them up and it would start pissing like a racehorse, so this morning I took it back to the dock (hoping to fish) and let it get up to temp and the telltale didn't improve a whole lot. Took it for a spin and it quickly started getting up past 170 so I turned around and packed up.

SO, impeller (and top housing), thermostats and poppet have been changed. Weird part is when I put the old stats back in that were slightly stuck open things actually looked better (telltale was peeing better).

Is there a way for me to check that least my impeller/housing are working good and water flow is good, so at least I can mark that off the list? Can I run without the stats to see if the telltale is strong? Will that tell me anything?

Pull thermostat housings off,pull stats.fire up engine,water should fire out of housings, try and direct flow of water away from engine electronics

The Thermostats only control the temp of your engine at low speed. The popit valve controls the temps at high speed. If the popit is not assembled correctly or you left the screw slightly loose the engine will over heat.

Like Johnnygjr said. if you pull the t-stat housings you should see water flow. Your tell tale should also be telling you something.

johnnygjr said:

Pull thermostat housings off,pull stats.fire up engine,water should fire out of housings, try and direct flow of water away from engine electronics

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How exactly should I do this? The 2 thermostats are daisy chained then run to the telltale, could I just pull the stats, put the housing back on and run a tube from each housing (so water is away from engine)? By "fire out", without the stats in and reassembled should a 1/4" tube from each housing still have a good flow of water?

taymag said:

How exactly should I do this? The 2 thermostats are daisy chained then run to the telltale, could I just pull the stats, put the housing back on and run a tube from each housing (so water is away from engine)? By "fire out", without the stats in and reassembled should a 1/4" tube from each housing still have a good flow of water?

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Just pull the covers and start the engine. You are just running the engine long enough to see if water comes out of the cylinder heads.

FYI Running your engine on flush muffs and a garden hose will most definitely over heat your engine if you run it long enough.

Docksidemarineservices said:

Just pull the covers and start the engine. You are just running the engine long enough to see if water comes out of the cylinder heads.

FYI Running your engine on flush muffs and a garden hose will most definitely over heat your engine if you run it long enough.

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OK, got around to doing this.. Kind of odd results....

So I ran some tubes off the thermostat housings (with the stats pulled) to check for flow out of the heads, PLENTY of water flows from each thermostat.

Double checked each thermostat, they expand fine (between 130-160 roughly).

Now the odd part (hopefully explainable for not odd to you guys), and yes the telltale hose and hole is 100% clear, when I fire it and let it get up to temp (even let it run past 160 to be sure) I still get less than desirable amount of flow from the telltale, especially considering the flow from my test.

Engine is still getting too hot, and when I throttle up I do get more flow so I assume my poppet replacement is working, but even if it isn't wouldn't I still get telltale flow idling since the stats should be plenty open?

I have put most my focus on the stats cause it just doesn't make sense that the flow isn't strong idling knowing I have water coming from the heads and have used 2 sets of stats, but should I look at the impeller and poppet again? Just seems like EVEN IF they are no good (they should be, they are new) I should still get telltale flow considering the heads flow without the stats

Thanks for the help, would reallyyyy hate to take it to the shop for this, seems so damn simple

Have you checked the grommet where the water tube goes into the powerhead? A leak there could cause this issue.

When I take the lower unit off engines I run a hose and zip tie it tight to the water tube, then cut the water on. You shouldn't have water running back down the water tube or you have a leak in the grommet. I have had them fail before. Just a thought.

What is the serial number of this engine so I can pull up the diagram?

Start from the water pump and work you way to the Popit, Pull the lower, take the pump and wear plate off and post pictures of the housing. Pay attention to the water tube, is the end of the tube rotted off?

And Like rotus623 asked, post the serial number.

How do you know its to hot???? Is hot alarm going off??? A 2.5 motor will not "P" till the t-stats open this could be several minutes depending on water temp. NEVER go by the temp guage as these are not accurate...

Try using an infrared heat gun on heads to make sure she's not running too hot, Harbor Freight has them 20.00 bucks, Is the telltale stream so hot you can't keep your hand in it,"too hot". Is there any sign of steam in exhaust? Are plugs super white "steamed cleaned"? Run a compression test to verify you have an intact head gasket, Keep us posted.