What did I do wrong?
 

I put a set of intake gaskets on my '94 350 mag/alpha today and now its running like crap. Runs rough and doesn't sound right. As far as I can tell, everything is hooked back up as it should be. Timing is set at 8 deg BTDC using a light, and I'm holding 18 inches of vaccum at idle. Help me out here guys.

This is what it sounded like before with it idled up a touch:


http://i868.photobucket.com/albums/a...h_a345ac95.jpg

This is what it sounds like now:

http://i868.photobucket.com/albums/a...h_965b7ddf.jpg

Also, my starboard exhaust riser gasket was leaking, so I ordered a new one from sierra.
This is the one that it had on it:
http://i868.photobucket.com/albums/a...d/b239d326.jpg

This is the one I put on it:
http://i868.photobucket.com/albums/a...d/148d5119.jpg

What is the purpose of the restricted gasket? As of this second it has the 2 different gaskets on it, but I wanted to find out what the purpose of each one was. I can tell ya the exhaust riser is ice cold now, even with it running. lol

Plugs wires correct?

Yeah, I never removed any wires. Took the cap off with the wires still connected and layed it to the side

could the cap have gotten wet? might take it off and spray the inside down with WD40. seems like ignition as the other post alluded to.

Not likely, the cap was only off for around 2 hours and it was laying away from the block. It looked dry when I put it back on.

Well...the only thing that you changed was the intake manifold gaskets. I vote for vacuum leak. While it's running try spraying WD40 along every gasket...if the engine sound changes there's your leak.

Using correct timing mark?

It holds steady at 18 inches of vacuum at idle. Is that not sufficient?

motor sounds real lazy to me . i would have to say the timing is way off .turn the dist ccw while its running and see if it wakes up

Yeah, 4 marks to the left of 0 on the timing tab.

Quick question, do these have a timing advance that needs to be unplugged while checking the timing like an automotive engine?

I did try turning the distributor both ways as far as it would go until it nearly killed the engine, and the rpm would change a little, but still ran rough.

fixx
 

what year?

'94

If it is thunder bolt v You have to follow a certain procedure. Here is a link to it.

http://forums.iboats.com/showthread.php?t=207665

Ok, I'll have to recheck my timing. I'm positive that it still isn't the root cause as I have turned the distributor as far as I could both ways and the miss never cleared up.

i'm gonna get the dunce hat for this one, but i think it's the gasket.

in video 1 water is coming from the propellor hub and transom assembly bypass. as it should out of the box

in video 2 alot of water is coming from the bypass on the transom assembly, and none from the prop hub.

on stock mercruiser ex manifolds water mixes w/ exhaust gas right at the end of the riser around it's perimeter,

the new gasket flows more water since you said the riser is cold
if more water got introduced into the exhaust couldn't it be sucking some back into the engine causing it to run rough,

this is kinda what I'm thinking also. I have the correct gasket ordered for it. I hope thats all it is

Be easy enough to check, pull your dipstick

I don't know much about these ignitions. Which one do I have?

http://i868.photobucket.com/albums/a...d/cb80b418.jpg

You might be right.

Start checking every wire and connection and anything that that you moved or touched. Why is there a black/ground wire laying on top of the dist and not connected to anything???? and a purple(key on hot) wire laying across/on top of the shift linkage???

they werent connected to anything before....

Look at the ignition module, it is mounted to the exhaust riser on the port side (passenger side) of the engine, opposite side of the engine of the shift linkage. It will clearly state if it is thunder bolt IV or V. Should be V unless somebody changed it. V has a knock sensor, IV does not. Maybe other differences but I am not aware of them.

It is a Thunderbolt IV

Looks to be a black unconnected ground wire and if its got a connector like that and its not bolted down as a ground or such the install might still be in error?
Check the plug wire connection on cylinder #5 and #7, many times these two get crossed because they are right next to each other in the firing order and I've seen some run like this with that cross-up.

Best Regards,
Ray @ Raylar

I'll double check the wires, but none of them were ever removed from the cap or the plugs and it didn't run like this before.

I have a ground wire going to one of my cap bolts

I got the correct riser gasket for it today, so I'll get it changed and try hooking that ground up to a cap bolt. That ground and hot wire werent hooked up to anything before. It's worth a shot I suppose.

what is on the other end of the ground wire? purple is probably trim limit. supposed to stop you from trimming up at a certain point when in gear. probably bypassed.

A ground :lolhit:

kinda what i am asking. if it is bolted to ground, he needs to find out what it is supposed to ground. if it comes from something else, it needs to be grounded to do it's job. if other end is bolted to ground, grounding the free end will do nothing.

Purple wire is an ignition 12+ it probably goes to your choke.

Purple/white might be a trim limit but it probably would not be next to your distributor.

it has a vacuum operated choke

What is your idle speed when setting base timing?

~700rpm

Distributor was removed to remove intake. Could it be off one tooth.

why did you need intake gaskets in the 1st place? Replacing them with new did you torque the intake manifold bolts in the correct pattern and correct torque in 3 passes.

Maybe an air intake leak at the manifold or water leaking into a cylinder or 2. from improper manifold gasket seal. What does your spark plugs look like ? any water on them or spraying out of the cylinder/s.

Also make sure that the ignition sensor under the distributor is hooked up correctly and grounded correctly. If this is the orignal sensor under the dist. cap I would replace it anyways. Merc had a SB years ago for a newer style sensor to replace the old one.

Next put some inline sparkies to make sure you have fire in all spark plug leads. You can also use a timing light for this while the motor is running plus check for misfires.

Timing should be good then, assuming distributor is in correctly as was just mentioned in an above post

Agree with Rookie the purple wire is 12 V and hook up for an electric choke app. The Purple and a black wire are for electric choke as in this app they hook to nothing being a 4 bbl manual choke app. It is pre wired and used in the 2 BBL carb apps for an electric choke.

The reason - Merc can use the same wiring harnesses thru out whatever the carb app is going to be. If the choke is manual leave the puple & black unhooked and if its the 2 bbl carb with electric choke the purple gets pushed hooked and the black screws on. Now you know where those 2 wires go.

Anytime a marine motor is work on at a true marine shop the first thing the tech does is look up the motor serial # to make sure he knows what he has.

This also helps with parts look up and what OEM service manual to look into for service help & specs if needed.

It makes no difference what year the hull is. Post your motor serial # inwhich can help out others that are trying to help fix it. The pics are somewhat hard to see what wiring is hooked into what wiring and so forth. Good luck with it.

Engine Serial Number is OF284281