Mercruiser 5.0 50 degrees at idle

[Rap1404]

Hey guys! Long time reader but first time poster.

I have a 99 rinker with a mercruiser 5.0 carbed vortec with a thunderbolt 5 ignition, i was changing all the ignition related items (sensor, plugs, wires and cap/rotor) and not I cant seem to get it timed correctly.
I put it on base timing mode but it doesnt run right if its not around 40-50 degrees advanced, when I try to set it to 8 degrees it runs horribly and stalls. I have brought the #1 cylinder to tdc and moved the distributor base to match the #1 post on the cap, maybe i need to take out the distributor and set that correctly?
Thanks in advance

Rei

 

[Bt Doctur]

With number 1 at TDC compression you line up the rotor tip to where number plug wire is at the cap. Most have it at #1 on the cap.Some put it anywhere and jumble the plug wires to match
Firing order is 1,8,4,3,6,5,7,2 clockwise

 

[stang32]

You have to be connected to the wrong wire. port side front plug is where you should be connected. , if so, try another timing light

 

[achris]

If you're on #2 instead of #1, then it's going to look like about 50 degrees... Make sure you're on the correct spark plug lead.

 

[Rap1404]

I just redid TDC on #1 and set the distrutor to point at number 1 and im still reading 40 degrees advance at idle. I also redid the wires and have a new coil and pickup sensor, im puzzled idk what to do.

Thanks guys

 

[dubs283]

Make sure you're on #1 compression TDC, could be you're on the exhaust stroke and possibly wrong firing order. A LH rotation sbc will run at multiple firing orders, I've seen it. Once tried to get a reman engine running right and based on vintage/frankenmotor status tried many different firing orders, 8-10 iirc. Amazing part was the engine ran at about 4 different firing orders but would only idle at 30-50 degrees btdc. Turns out the long block/cam timing was off a bit, a testament to American engine runnability.

Keep in mind the rotor turns clockwise looking down from above. 18436572

 

[Rap1404]

Make sure you're on #1 compression TDC, could be you're on the exhaust stroke and possibly wrong firing order. A LH rotation sbc will run at multiple firing orders, I've seen it. Once tried to get a reman engine running right and based on vintage/frankenmotor status tried many different firing orders, 8-10 iirc. Amazing part was the engine ran at about 4 different firing orders but would only idle at 30-50 degrees btdc. Turns out the long block/cam timing was off a bit, a testament to American engine runnability.

Keep in mind the rotor turns clockwise looking down from above. 18436572

The weird thing is that ive set the timing on this engine before and has been fairly easy, thats why im thinking this might be a part thats defective? I cranked the engine until it blew air out of my finger and then set the engine to the line on the balancer, like i said ive done this several times before thats why im puzzled as to what this is.

 

[dubs283]

im thinking this might be a part thats defective?..... i said ive done this several times before thats why im puzzled as to what this is.

If there is an issue with timing/runnability on a thunderbolt ignition with sound fuel delivery the most likely culprit is the ignition sensor in the distributor. So many I've replaced over the years. Go oem, three wire with a dedicated solid ground to same post/stud on flywheel cover as battery ground. Pretty sure this will solve most of your issue, best bet is a full tune up along with sensor replacement, not forgetting fuel filters/inspection of course

 

[alldodge]

The weird thing is that ive set the timing on this engine before and has been fairly easy, thats why im thinking this might be a part thats defective? I cranked the engine until it blew air out of my finger and then set the engine to the line on the balancer, like i said ive done this several times before thats why im puzzled as to what this is.

Balancer may have slipped

To verify may need a piston stop bolt

 

[dubs283]

Balancer may have slipped

To verify may need a piston stop bolt

Unlikely, however I'm curious, is a piston stop bolt a tool most used for rebuild or complete package troubleshooting?

Am truly interested, no snark intended and I've read reference to said tool in recent threads. Just wondering the veracity of the tool

 

[achris]

When setting up the old Merc 'link and sync' and piston stop was required to set the timing pointer.

 

[Rap1404]

If there is an issue with timing/runnability on a thunderbolt ignition with sound fuel delivery the most likely culprit is the ignition sensor in the distributor. So many I've replaced over the years. Go oem, three wire with a dedicated solid ground to same post/stud on flywheel cover as battery ground. Pretty sure this will solve most of your issue, best bet is a full tune up along with sensor replacement, not forgetting fuel filters/inspection of course

I just replaced the cables, cap and rotor, sensor and coil (all oem) now i also think it might be the sensor. The rotor shows scratches like it was rubbing against the sensor, i checked it again while cranking with the cap off but it looked ok. Since we're talking about base timing it would be the module would it? Maybe ill get another sensor and try it, do these fail alot?

 

[Rap1404]

To give you guys the whole story... the boat was running great and i decided to buy a fuel injection kit from affordable fuel injection, the engine never started to i decided to replace all those parts to no avail. Then i took off the kit and but the carb back on, it now starts but the timing is wayy off. Maybe it is the sensor.... thats why it didnt start with the new ignition module with the efi and it doesnt set timing correctly with the carb?

 

[tank1949]

The weird thing is that ive set the timing on this engine before and has been fairly easy, thats why im thinking this might be a part thats defective? I cranked the engine until it blew air out of my finger and then set the engine to the line on the balancer, like i said ive done this several times before thats why im puzzled as to what this is.

you should pull valve covers (to examine) and rotate motor base when #1 piston is on top of compression stroke. Watch rocker arms and distributor rotor. Then, examine rotor to see if it remotely pointed to #1 CONTACT. Pray that you haven't jumped time.

 

[alldodge]

To give you guys the whole story... the boat was running great and i decided to buy a fuel injection kit from affordable fuel injection, the engine never started to i decided to replace all those parts to no avail. Then i took off the kit and but the carb back on, it now starts but the timing is wayy off. Maybe it is the sensor.... thats why it didnt start with the new ignition module with the efi and it doesnt set timing correctly with the carb?

For the timing to be 50* advance either the balancer has moved or your using the wrong plug to set timing (Ford/Chevy thing, Chris post 4). Only way I know without taking the head off to find exact TDC is with a stop bolt.

 

[Rap1404]

For the timing to be 50* advance either the balancer has moved or your using the wrong plug to set timing (Ford/Chevy thing, Chris post 4). Only way I know without taking the head off to find exact TDC is with a stop bolt.

Would a bad sensor cause this? Should i try to replace it again?

 

[alldodge]

Would a bad sensor cause this? Should i try to replace it again?

Don't see a sensor causing a 50* advance
If there is an actual 50* advance seen then need to find out why. Maybe the timing light is the problem, right now no one knows, were just guessing based on your info

 

[Rap1404]

Don't see a sensor causing a 50* advance
If there is an actual 50* advance seen then need to find out why. Maybe the timing light is the problem, right now no one knows, were just guessing based on your info

 

[Rap1404]

Don't see a sensor causing a 50* advance
If there is an actual 50* advance seen then need to find out why. Maybe the timing light is the problem, right now no one knows, were just guessing based on your info

I was kinda hoping it would be that. Then take off the valve covers and check back?

 

[alldodge]

I was kinda hoping it would be that. Then take off the valve covers and check back?

The valve cover look gets close. Valves close and the mark on damper will be about 180* away. I say about because there is cam lobe variations. With all spark plugs out rotate crank by hand and have a wire or something in number 1 cylinder. Slowly crank it up till the wire is not pushed out any further, this should be close