Heads up on poppet valves in Black Max

[dingbat]

I've got a "86" 175 Merc whose cooling system has gotten a lot of attention lately so I wanted to bring this to peoples attention.<br /><br />I started getting a strange pressure "bounce" and an erratic flow out the pi$$er that looked like cavitation of the water pump or even air lock of the cooling jackets when running between 1000-2000 rpm. Just about everything in the cooling system was new this year so I ruled out a water pump or thermostat problem. The only thing I didn’t replace was the poppet which had been replaced 2 seasons earlier so I started looking for my problem there. <br /><br />I tore the poppet apart and found nothing visually wrong until I compared the old spring with the new one that came in the kit. The old spring had collapsed by about 20% or so in the two years it had been in there and worst yet, it broke in half as I was flexing it between my finger tips. I replaced poppet spring and diaphragm and everything is now back to normal now.<br /><br />It appears that poppet springs do go bad and it would be wise to included them your annual maintenance schedule to prevent future cooling system problems.

 

[achris]

Re: Heads up on poppet valves in Black Max

Good catch dingbat....

 

[rodbolt]

Re: Heads up on poppet valves in Black Max

its all maintenance. that is why your supposed to do it before it breaks. glad ya caught it in time. on a merc I reccomend a yearly diaphram replacement. I see a lot of blown motors due to a leaking diaphram. the lower carbs like to pick up the water mist and shortly thereafter its POOF.<br /> good luck and keep posting

 

[KCLOST]

Re: Heads up on poppet valves in Black Max

Dingbat, thanks for the note....<br /><br />But I would really like to know what kind of temperature changes occured as a result of that repair.<br />So, did that lower your temperatures only at rpms below 3000, WOT or even at idle??????<br /><br />What were they before and after????<br /><br />This would really help a lot of folks...<br /><br />By the way, salt water makes a big difference on that spring durability if that has come into your situation...

 

[dingbat]

Re: Heads up on poppet valves in Black Max

I've got no idea of the temp since I don't use a temp gauge but anytime you can increase the water flow through the heads you are bound to decrease the temperature. <br /><br />I live, eat and sleep saltwater and have seen more than my share of SW related failure but this was not one of them. I’m leaning more toward factory defect.