exhaust valve stuck open

[bigtoe]

hi volvo penta 3.0l GS the exhaust valve for the rear cylinder is stuck open. Ive zero pressure in it, other three are good showing at 175ish. I can hear air blowing out through the exhaust on a leak test. boat has sat most of the year and was fouling the carbs up something rotten when used for a few days last year. Carb is now sorted though so I thought all good to go. But heard it running on three and back fired through the carb a few times when revved. did the comp test and found this.
Is it difficult to free or should I take it to a mechanic for a head off strip down. ? thanks

 

[Scott Danforth]

not difficult if you know how to turn a wrench. first thing to do is pull the exhaust manifold. you will most likely find that the exhaust manifold is leaking into the exhaust port

 

[Bt Doctur]

Yes sir, one of the easiest was to ruin a exaust valve, leaky manifold or riser.

 

[kenny nunez]

Make sure that the stud of the exhaust valve rocker arm is the same height as the other studs. Most times with a stuck valve the stud pulls out a small amount. With brass drift and a hammer the stud can be driven back down.
Once the manifold is removed spray some penetrating oil on the valve stem.
Be sure the piston is down in the bore before the next step.
With the same hammer and drift try driving the valve further down while spraying the valve stem. Do not be surprised if the valve spring pops the valve back up. Quite often I have had luck un sticking the valve this way.
google the procedure to re adjust the valve. As AD and Boat Doctor stated a new manifold will give your engine a few more years.
if there is not too much rust on the valve and seat it may clear up once the engine is running.
Worse case if the valve does not pop back up the head has to come off.