Does anyone have pic of distributor on Merc 7.4 Gen V?

[CLi87]

I'm working on a 1993 Mercruiser 7.4 Gen V, it acts like it tries to start but will run for a second or too and then stop and backfire through the carb, I didn't touch the distributor, so I would think timing should be right, but the engine is new to me so no idea. I'm thinking the backfiring is either lean condition or timing is off and since I just cleaned the carb and it has a new rotor and cap, so I'm thinking maybe timing is off, currently the 8 on the distributor cap is pointed toward the number 1 cylinder, it's been awhile since I've timed one of these but I recall generally speaking the 1 on the distributor cap should be pointed slightly before the #1 cylinder? Was wondering if someone had a pic of the distributor alignment on their engine before I go through the trouble of re-timing the engine. Also I removed the spark plugs and checked them all and it seems cylinders 5 & 7 aren't firing at all, didn't see any wear on the spark plugs for those cylinders.

 

[San_Diego_SeaRay]

I'm working on a 1993 Mercruiser 7.4 Gen V, it acts like it tries to start but will run for a second or too and then stop and backfire through the carb, I didn't touch the distributor, so I would think timing should be right, but the engine is new to me so no idea. I'm thinking the backfiring is either lean condition or timing is off and since I just cleaned the carb and it has a new rotor and cap, so I'm thinking maybe timing is off, currently the 8 on the distributor cap is pointed toward the number 1 cylinder, it's been awhile since I've timed one of these but I recall generally speaking the 1 on the distributor cap should be pointed slightly before the #1 cylinder? Was wondering if someone had a pic of the distributor alignment on their engine before I go through the trouble of re-timing the engine. Also I removed the spark plugs and checked them all and it seems cylinders 5 & 7 aren't firing at all, didn't see any wear on the spark plugs for those cylinders.

I have a 93 Gen V 7.4 in my Chaparral but I don't think a picture would help. (And I don't have one at the moment). The distributor can be installed any way you want in a 360 degree manner, so long as, like you indicated, the rotor should be at or right before the #1 cylinder when it is at TDC on the compression stroke.

If I were you I'd just go through the motions of reinstalling the dizzy from scratch. Or read Don S's #7 in the Adults Only section. That basically tells you how to make sure the rotor is pointing to #1 when it is at TDC on compression.

After that, you would need to complete the timing procedure by disabling the Thunderbolt Ignition system and setting base timing.

 

[Bondo]

I'm working on a 1993 Mercruiser 7.4 Gen V, it acts like it tries to start but will run for a second or too and then stop and backfire through the carb, I didn't touch the distributor, so I would think timing should be right, but the engine is new to me so no idea. I'm thinking the backfiring is either lean condition or timing is off and since I just cleaned the carb and it has a new rotor and cap, so I'm thinking maybe timing is off, currently the 8 on the distributor cap is pointed toward the number 1 cylinder, it's been awhile since I've timed one of these but I recall generally speaking the 1 on the distributor cap should be pointed slightly before the #1 cylinder? Was wondering if someone had a pic of the distributor alignment on their engine before I go through the trouble of re-timing the engine. Also I removed the spark plugs and checked them all and it seems cylinders 5 & 7 aren't firing at all, didn't see any wear on the spark plugs for those cylinders.

Ayuh,.... Rebuilt or not, do you see gas goin' through the carb,..??

Sounds lean to me,....

 

[Scott Danforth]

Cylinders 5 and 7 could be steamed cleaned from water leaking into the ports

Verify your timing
Check compression (should be 150psi on all cylinders)
Check your fuel

 

[CLi87]

Found the issue, exhaust valve on cylinder #1 is stuck open, not sure what happened, I did a compression test when I first got the boat and compression was good, changed the oil pan gasket and rear main seal and now the exhaust valve is stuck open. Also there's no outdrive or water connected to the engine right now, I was just trying to start it for a few seconds before connecting everything back so it can't be an issue of water getting into cylinders.

 

[alldodge]

PO may have had the head machined and didn't check for length of push rod or might have put the wrong push rod in

 

[Scott Danforth]

Look for rust buildup on the valve stem