Merc 9.9 Cooling System Question

[Aquatect]

I have an early '90's 9.9 Two Stroke LS that doesn't start peeing out the indicator until it heats up and the thermostat opens. It stops when the heads cool but then starts peeing agian as they warm up. I checked the impeller and it's in good condition. I replaced the saltwater crusty thermostat but made no differance. None of my other outboards pee "intermittantly". They either do, or they don't and I fix them via usual remedies. When it does pee, the water is quite warm, bordering on hot and steams in 40 degree weather. I took the motor in trade and it runs great on the stand but doesn't behave like I want it to before putting it in service. Any thoughts?<br />Thanks,<br />Brian

 

[andy6374]

Re: Merc 9.9 Cooling System Question

The opening and closing of the t-stat is normal. However, when it is first started up you should have a little bit of a water stream out the tell-tale. Then when the t-stat opens you will get a full stream. <br /><br />You were on the right track replacing the t-stat, but while you had the L/U off you should have replaced at least the impeller. Change it out with some new gaskets to be safe. Like I said, you should have at least a little water out the tell-tale when it starts up.

 

[Aquatect]

Re: Merc 9.9 Cooling System Question

Thanks Andy,<br />You're right, I should have replaced the impeller kit, especially when I had all the new parts sitting on my bench. I was hoping to save them for another project but I'll pop the lower unit back off and update the parts in question. I think I'll try blowing compressed air through all the lines to clear any partial blockages. Thanks again. -Brian

 

[andy6374]

Re: Merc 9.9 Cooling System Question

Even better...with the L/U off, remove the t-stat housing and stick your garden hose down it. Watch for any falling debris out the water tube. Compressed air works as well, but I like this approach better.