Missing and no power under load

[brodie123]

Hi All;

2007 Mercruiser 4.3L V6 - Alpha 1 drive

- Rebuilt carb
- new plugs, dist cap and rotor
- new fuel filter
- drain and replaced gas with new
- compression is good

No power under load. Starts fine but rumbles. It appears that 2 cylinders are not firing. 1 of which comes in and out for about 2 minutes, then out for 2 minutes. When the 5th is running I am missing around 500+rpm, and when both are out I am missing around 1000+ rpm.

I assume there is an ignition controller - I have to DL the manual still but thought I would get some advice first.

Thanks in advance.

 

[alldodge]

Compression numbers please?

Engine serial number would be great

Guessing you have a carb but missing on 2 cylinders and have replaced cap, rotor and plugs. Now unless the wires are bad, then its a compression issue

 

[brodie123]

All 6 cylinders are at 175lbs after 4 turns on each - they seemed very consistent.

Suggestions???

 

[Bondo]

Suggestions???

Ayuh,..... Ya missed something in yer carb rebuild,.....

 

[alldodge]

Serial number?

Have you checked timing and if so did you place motor in base timing?

Double check the firing order?

 

[brodie123]

I'm up north in the middle of no-where trying to help my dad with his boat.

The carb rebuild was done at a carb specialty shop - I always use them as they are very good.

I don't have my timing gun - but we are seeing if we can borrow one.

The engine calls for MR43LTS and what was installed was AC Delco 12607234 which I believe is a colder plug. I can't find the right plugs anywhere near us - best I can find is Champion RS12YC.

I tested for spark with a different plug and had good spark. I tested the installed plugs and they seemed weak.

All I think I can do is check the timing and go with champion plugs. Any thoughts on that? I have limited options other than for him to be stuck for 4 weeks until I get back up north.

 

[alldodge]

I'll say this IF your motor calls for MR43LTS then there is no issue what so ever using RS12YC. There is nothing wrong with Champion plugs and I like them

 

[brodie123]

Thanks everyone. After doing everything, and I mean everything short of pulling the engine apart, she is now running 'better' than new. lol I really appreciate the feedback and it helped.

 

[Bt Doctur]

does this use the flat crab type dist cap?

 

[brodie123]

No - standard style of cap. I'm curious if there is a reason for the question? i.e. crab style has issues or something??

 

[gergAlicious]

So the plugs did the trick?

 

[alldodge]

No - standard style of cap. I'm curious if there is a reason for the question? i.e. crab style has issues or something??

The flat caps go bad quite often, they can look great and still have issues

 

[Bt Doctur]

and the plug wiring order is not what it seems

 

[brodie123]

Good to know. I will avoid those then!