the older ignition sensor assembly under the cap & rotor did not have a separate dedicated ground wire. the newer ones do. you most likely had a bad sensor taking place. good luck with engine hope its not bad. what was smoking ? did an impeller let go ? or was it oil burning that caused the smoke ?

Ok, I'm about out of ideas. Could use some fresh ones.

What I've done since last post when I realized it was a spark problem. I replaced EVERYTHING that has to do with making a spark. All with brand new parts. Even replaced things I replaced when I rebuilt the motor, just incase.

Today it got,
- New Hall Effect sensor inside distributor. Didn't replace actual distributor, but did check that the pin holding the gear on was not broken, and checked there wasn't excessive play. Replaced with Siera brand, which is reported better quality as its a sealed unit with its own ground..
- New Coil
- New Cap, Rotor and gasket.
- New Mercruiser Plug wires.

Got engine to start. Could tell was only running on a couple cylinders. Went to check timing, #1 plug wasn't firing at all. Hooked up to a couple other plug wires, found at least 1 more that wasn't, found a couple that were.

Took plug out of #1 cylinder. Attached a ground to it and started engine. Ran just as was running before. Sparked first time engine turned over, not after.

Hooked jumper cables from battery to engine ground, make sure it wasn't a ground issue. No change.

Tried a different computer. No change.

Timing seems to be off from where it was before. Thought maybe I was just off a tooth putting distributor in, but it won't go in off just a tooth or two because of slot for oil pump.

Very confused

This is a long shot but it's a fresh idea: I wonder if the gear to turn your distributor is damaged?

Captain YARRR,

Not ruling anything out at this point, but it was in good shape when I put the motor back together. Also turned motor over with cap off to watch distributor position.

Had a brief dumb moment not thinking what that slot was going into. Took a long screwdriver and turned it so I could put the distributor where I wanted it.

After 4 more hours of work, this is what I've learned...

- Ohm'd all grounds. All good. Even ground pins at ECU are good.
- Voltage at coil good.
- Not getting spark was because of distributor position. Rotor was just too far away from the tab when it was firing. Rotated distributor a little, got spark.
- With thunderbolt setup, it doesn't matter what slot the distributor is in, you just rotate it until #1 is where it needs to be.
- Got the engine to run (poorly) by trying all different distributor positions. Found the best place, put on timing light, was about 120 deg away from TDC. Took plug out, found tdc on compression stroke, reset distributor, nothing. moved distributor all around that area, nothing.

I'm now convinced its a mechanical problem. Going to pull motor. My Master Tech advice friend told me I should pull valve covers first and check base timing by rotor position and valve positions, but then I realized, if it looks good, then I'm pulling motor to investigate things further. If there is a problem, obviously I'm pulling the motor. So would rather do all that testing no laying over the back seat of the boat.

Any updates?

did you check cam timing against crankshaft? (#1 piston at TDC in relation to intake valve start open on #1 cylinder)

Hey I totally forgot about this as it hit me today working on boats about what you said inn post # 1 - your fuel pressure is 30 psi and you have have Mercruiser service manual # 31 supplement.

here is the deal - YOUR - FUEL PRESSURE is the problem - the MERCRUISER Service manual # 31 and # 31 supplement list the wrong the fuel pressure of 30 psi. IT SHOULD BE 43 psi. Also there is a Mercruiser Service Bulletin all about and I will see if I can something on line to post as to what I am talking about. Your problem is way too low fuel pressure. it needs to maintain 43 psi thru out.

Found it , read it as Mercruiser misprinted the proper fuel pressure in the service manual 31 and 31 supplement,

Again it needs to be 43 psi. I can not believe I did not pick up on this ASAP from your post # 1. Heck I know this already from back in the day to current.


https://docs.google.com/viewerng/vie...-EFI_EN_10.pdf

Sorry no update for a little bit. Motor has been in and out of the boat 4 times in the last couple weeks.

Took off timing chain cover and oil pan. Timing gears lined up perfect. Inspected for anything broken. Everything looked great.
Redid valve adjustment. Checked compression again, all cylinders 170-180psi.
With timing set where it should be, motor won't start at all. With distributor majorly advanced, engine will start with about 1/3 throttle and idle (barely). Timing light shows its firing about 60-80deg after TDC.

Checked all voltages and grounds. Everything good.

Did wiggle test of everything while motor was running. while doing that, engine roared to life for a couple seconds. Reduced throttle, engine died. Could not duplicate.
Replaced entire wiring harness. Did not solve problem.

Wanted to test injectors, so I swapped the entire intake with other motor. This also eliminated many sensors as possible problem. No change.

Before reading your post BUP, I had already decided to change the fuel pump. Mainly because I have nothing else to replace.

I had seen a post somewhere about another manufacturer that makes the exact same pump, but can't find where I saw that now. Anyone know?