inlinepwr

Not sure what computer it is but the distributor is the flat top which is new this year with many temperature hrs. On it. Maybe the picts. Will help identify the computer.[IMG][/IMG]
[IMG][/IMG]

inlinepwr

The paperwork I have on the motor says ignition timing is fixed, not adjustable. Cam retard 15+2 degrees.

SB

iTrader: (1)

That's the 555 computer. You will need a scanner to change the 'cam retard.' That's usually done by turning the 'distributor' as the 'distributor' is the cam sensor.

Maybe BUP or someone else with the instruvtions will chime in.

In the meantime, do you know someone (personal or nearby marina) that has a scan tool and can help you with this ?

Mr Maine

Nice exhaust. Sounds like the timing in my late 90s chevy truck..get distibutor close and the computer takes over. I could turn my distributor back in forth a bit with no change on the timing light as the engine compensates for it.

inlinepwr

So do you think it sounds like a timing issue or it not running on all 8?

BUP

iTrader: (9)

Hey I read about 5 posts up AND WILL add throw your timing lite back in your tool box

ALL ECM 555 and PCM 555 TIMING is NON ADJUSTABLE as all spark is controlled by the ECM / PCM and for ECM 555 has the HVS = High Voltage Switch (distributor NON tech words here) the HVS just sends the spark.

This has to be properly phased (HVS) if moved or pulled out in which yours was pulled out for heads. You have to look for cam angle on the scan as well. If this phased HVS / and cam angle off the very slightest your engine will revert water plus run poorly . Also will add HVS not properly phase will not run correctly or can run fine up to a certain rpm - then after that certain rpm could even go into limp mode or engine shut down depending how far off the HVS phased / cam angle is off. And even cause no start conditions being not phased properly


the HVS has to be pulled back out and phased properly when reinstalling then engine scanned while running to check cam angle to. Mercruiser also has an indepth service bulletin all about phasing the HVS for ECM 555.


with that said do you still have the HVS / stock ignition parts installed if not what do you have and what is installed. ECM 555 is tuned for the HVS and the cam angle among a crap load of other parameters.

More info and indepth when I get a chance. freakin rain break time at the moment.

BUP

iTrader: (9)

I just reread your post and runs rough and how you reinstalled your HVS back in is not the correct procedure at all - now I know for sure your engine running problems

I will bet a box donuts your HVS is off phased and cam angle is causing your water reversion and your rough running- I am 99.999% sure of it

The tiny bit of question to ask as well is did you switched some of the ignition stock components to NON stock installs.

the HVS Cap and rotor are very important here. Some call it the crab cap we call the flat cap or HVS cap in which It is called from mercruiser. they need to be change every so often. A tip in top of

Does your ECM 555 have the stock tune ?

Have to ask all of this because I do not know how your engine is set up and see SM exhaust system so asking some other questions here as well.

BUP

iTrader: (9)

4 bus this is ECM 555 there is a big difference pcm 555 is coil over plug and a lot more for the jist.

BUP

iTrader: (9)

Also to the OP you have another fuel & water sep filter added in the mix (a yamaha fuel filter added) into the mix and the stock mercruiser fuel & water sep filter. That is one way to fuel starve and lean your engines hence possible Valve job problem that was created.

Mercruiser pre warns NEVER add addition fuel filters of any kind in the mix on top of there systems. They report a sure way for lean conditions

Plus you added a bunch more of L angle fuel fittings - a sure way for lowering fuel volume and lean conditions

another tip on top of here.

inlinepwr

Dude you got my head spinning now. Thanks for the input I'll try to answer your questions. I thought I was doing good by installing the extra fuel filter, that will be coming off tomorrow. The motor had a complete tune up at the beginning of the year including cap rotor and fuel filterS. The motor is completely stock other than the exhaust which was added because I've been having a problem with reversion since day one. This is why the heads were removed. I was carfull to reinstall the distributor the way it was removed. Nether the crank or distributer were turned while separated. So basically your advice is its nothing I can correct without a scan tool?