72 Mercruiser 165 inline 6 I/O runs great then rough and keeps shutting off'

[tlocus73]

Hello,
Trying to troubleshoot my friends 1972 Mercruiser I/O 165.
When we first take it out for a test cruise it runs perfect. Then after about 30 minutes coming back to the dock it begins to run rough and keeps shutting off.
It doesn't overheat.
Tied to the dock, starting it, it has a tough time staying idling. We also notice the exhaust is throwing out (gas?) in the water.
Also appears to have some water in the oil, looking at the dipstick...
He thinks maybe one possibility is the head gasket is leaking?

Any help or suggestions are welcome,

thomas

 

[alldodge]

Hello,
Trying to troubleshoot my friends 1972 Mercruiser I/O 165.
When we first take it out for a test cruise it runs perfect. Then after about 30 minutes coming back to the dock it begins to run rough and keeps shutting off.
It doesn't overheat.
Tied to the dock, starting it, it has a tough time staying idling. We also notice the exhaust is throwing out (gas?) in the water.
Also appears to have some water in the oil, looking at the dipstick...
He thinks maybe one possibility is the head gasket is leaking?

Any help or suggestions are welcome,

thomas

I see a compression test in your future. Also seeing raw fuel out the back check to see if your fuel pump diaphragm has ruptured, or the carb is flooding

 

[tlocus73]

I see a compression test in your future. Also seeing raw fuel out the back check to see if your fuel pump diaphragm has ruptured, or the carb is flooding

Thanks for the reply.
We did a compression check but not right after the above. We ran one just warming the engine for 5-10 min., removed all plugs, WOT, etc.. and got:
(if I recall the numbers) 150 & 160(middle plugs) and only 10 max psi difference between all 6.
On the inline 6 we also noticed the plugs on the ends; 6,5 and 2,1 looked good with a light tan coloring. The middle plugs had black dry carbon on them.
We'll check out the fuel pump and carb as you mentioned.

Welcome any additional suggestions as well..

t