350 Mag engine miss
 

I have 94 sea ray with a 350 mag and the engine has a miss. I changed the plugs(one was bad) and the fuel filter(which was clogged with crap). It runs better but still not right. There is a small peck at idle that you can hear in the second video, but goes away with any throttle input. I put a vacuum gauge on it this morning and this is my results.
There is a small amount of "blowby" coming from the pcv valves.
http://i868.photobucket.com/albums/a...d/634fe181.mp4 http://i868.photobucket.com/albums/a...d/07750509.mp4

Photos would not work for me.

I would check the cap and rotor and the plug wire for the plug that was fouled.

Also might be an issue on that cylinder, probably should do a compression test on all cylinders.

How many inches of vacuum did you have at idle

The electrode in the plug was comlpetely gone. I have a new cap/rotor, and carb kit ordered that should be in tomorrow. I'm gonna do a compression check in the morning. The gauge was bouncing really fast between 15-17. Never could get a steady reading.

Perhaps the vacuum oscillation is a burned or tuliped exhaust valve associated with high cyl temps that burned the spark plug electrode..just an idea..

Lane

thats what I'm afraid of. I'll get a better idea tomorrow once I do the compression test. :(

this is the spark plug from #2 cylinder.

http://i868.photobucket.com/albums/a..._Wood/plug.jpg

A bad valve without a burned piston and cylinder scoring might be as good as it gets...

Check out the table at the bottom of this page and the scenarios for vacuum reads:

http://www.secondchancegarage.com/public/186.cfm

Its not looking good. #2 cylinder has zero compression.

Could still be a bad valve, but doesn't look good. Let us know how it looks when you pull the head

Here is the story. I bought this boat about 2 weeks ago at a dealer local. Before I bought it, I did listen to it run, but didnt notice anything out of the ordinary. I took it out the next day and as soon as I came out of the no wake zone for the first time and brought it up on plane, I knew something wasnt right, as it was missing pretty bad. So once I got it home, I checked the fuel filter and spark plugs. The fuel filter had so much crap in it, I dont even see how the thing was running. All of the plugs looked good excpet the number 2 plug which is the pic posted above. I pulled the distributor cap and it was corroded pretty bad, so I cleaned it up and put it back together. It still wasnt running right after that. Thats when I decided to check the vacuum and found out I may have bigger problems than just a tune up. Next was the compression test, which I did yesterday and found no compression on number 2. So I immediately got on the phone with the dealer. He told me to bring it up there and he would check it out. At this point Im pretty upset because I have vacation starting this sunday that revolves around my boat. So Im thinking the dealer is gonna have this thing forever and try to charge me **** load of money to fix it. It was around 12pm when I dropped it off yesterday. He called me a few minutes ago to let me know the head had already been yanked and they found an exhaust valve tuliped on number 2 and the machine shop already had the head and the boat should be ready to pick up tomorrow. I realized that I did sign the as-is no warranty paper work when I bought it, but the dealer is gonna work with me as we reached an agreement that I would take care of the parts if he covered the labor. Fact of the matter is, the boat should have been checked more thoroughly and at the least a tune up done on it before it was ever sold, but I did talk them way down on the price so I am willing to take care of the parts to fix it, because I just want to have a boat that I can enjoy.

Sorry to hear the background ..but sounds like they are working with you quickly.
A good machine shop will inspect all the valves..but not sure what your dealer is telling them..I would replace all the exhaust valves (they are relatively inexpensive- upgrade to stainless if possible) and ask for a full valve job (grind seats, inspect guides, new seals etc) on that head as long as its out.
The other head is probably not far behind...not sure how much you can get done now..
How many hours on the engine..200+ or so is where I have seen stock valves tulip.