Nylon Balls

DONTGAF

Seaman Apprentice
Joined
Nov 20, 2008
Messages
30
Can anyone tell me what the purpose of the nylon balls inside the thermostat housing is.

Thanks
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Nylon Balls

Restrict the amount of flow going to the manifolds and risers, so there is enough water to cool the engine when needed.
In later models, without the balls, there are drilled passages of the correct size.
 

Alpheus

Lieutenant Commander
Joined
Aug 3, 2009
Messages
1,757
Re: Nylon Balls

When the thermostat is closed, the water exits through the check ball outlets, then flows to the risers, skipping the exhaust manifolds. When the thermostat opens, the check balls provide some back pressure to push water through out the block and out the non-check ball outlets. These are typically plumbed to the exhaust manifold. You NEED the check balls to get good flow through the block.
In later years, Mercruiser redesigned the thermostat housing to eliminate the need for the check balls...

OOPS I didnt see you answered Don.
 

DONTGAF

Seaman Apprentice
Joined
Nov 20, 2008
Messages
30
Re: Nylon Balls

Thanks guys this is just a preview of my next post "overheating troubles"
 
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