How much exhust and water should come out of prop on Merc 170 when running at idle

[stufferron]

When running my 85 Seville Merc 170 at idle in driveway with muffs connected to lower unit how much exhaust should be coming out of the prop? I thought that the relief vents at the top of the lower unit were there to expel exhaust and water when idling while in the water due to water presure against the prop exhaust. Shouldn't exhaust and water come out at the prop when on land. I am concerned there may be some obsturction somewhere that is preventing exhaust from exiting the prop. I get all the exhaust from the vents only. The engine just seems to be very hot to the touch which makes me thing the exhaust is backing up. Engine is running loud and rough.

 

[Don S]

Re: How much exhust and water should come out of prop on Merc 170 when running at idl

Depending on how much angle on the drive and the boat, maybe nothing will come out the prop, and it'll all come out the idle relief ports on the transom shield. Water takes the path of least resistance. At idle, there is very little pressure to push water up so it will come out of the prop.