mercruiser 470 a/f in oil

jabfd

Petty Officer 1st Class
Joined
Oct 2, 2012
Messages
221
hello everybody

Ive been dealing with this problem since last season a/f getting in to my oil i pressure tested the system and it loses pressure.
last season i changed the exhuast manifold to aluminium one because i could not get the old cast one to seal up at the riser gasket. so i upgraded to a use aluminum one presure test before i put it on it held after taking the boat out for a run got back to the dock and a/f was low pressure tested again losing pressure. I removed exhaust manifold tested on bench and it loses pressure around the gasket replaced gasket still does not seal up tried two gasket still no luck .
also ran a wire up the weep hole about two inches no a/f leaking out of that .

my question to everybody is while i had the riser off i presure tested the engine for 5min at 15 psi and it did not drop in presure can a head gasket not leak cold but leak when warm ?

sorry this is long but just trying to rule out if this is just a riser gasket problem or something else also i did a compresion test and all where between 145 and 155 thank you in advance for all your help
 

jabfd

Petty Officer 1st Class
Joined
Oct 2, 2012
Messages
221
Re: mercruiser 470 a/f in oil

hello everybody

Ive been dealing with this problem since last season a/f getting in to my oil i pressure tested the system and it loses pressure.
last season i changed the exhuast manifold to aluminium one because i could not get the old cast one to seal up at the riser gasket. so i upgraded to a use aluminum one presure test before i put it on it held after taking the boat out for a run got back to the dock and a/f was low pressure tested again losing pressure. I removed exhaust manifold tested on bench and it loses pressure around the gasket replaced gasket still does not seal up tried two gasket still no luck .
also ran a wire up the weep hole about two inches no a/f leaking out of that .

my question to everybody is while i had the riser off i presure tested the engine for 5min at 15 psi and it did not drop in presure can a head gasket not leak cold but leak when warm ?

sorry this is long but just trying to rule out if this is just a riser gasket problem or something else also i did a compresion test and all where between 145 and 155 thank you in advance for all your help

any help would be great
 

agallant80

Commander
Joined
Oct 25, 2010
Messages
2,328
Re: mercruiser 470 a/f in oil

Im not really a hard core engine guy but did you have the new head and old block machined before you attached them togeather?
 

jabfd

Petty Officer 1st Class
Joined
Oct 2, 2012
Messages
221
Re: mercruiser 470 a/f in oil

Im not really a hard core engine guy but did you have the new head and old block machined before you attached them togeather?

i never changed the head gasket just the exhaust manifold
 
Joined
Mar 27, 2010
Messages
3,008
Re: mercruiser 470 a/f in oil

Attached is the page from the manual regarding water in the engine, both above and below the pistons
 

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