Ace snake

Thanks GF ,
I checked the fuses and all 5 yellow 20A ones are good , took the belt off the supercharger and the pulley rotates freely with no weird noises .
measured resistance in the IAC and was a reading , changed MAP with good one , put new gas in the saddle tank and tried .Iac on bad engine getting power and moving !
fuel pressure is 65 psi on both engines ,so normal.pcm from bad engine is on good engine and running good.

Engine is running rich and lots of black soot .and no power at all !

still problem unsolved ??? could it be the boost valve ? could it be the supercharger ?

i am out of ideas and the mech too ?????;-((


what would a bad fuel pressure sensor do ? wouldnt the engine run badly despite the fuel pressure being good ?

Ace snake

can it be the mechanical fuel pump ? i had run that engine dry with no fuel a week before but motor ran fine for 30 mins after adding fuel

Update : We seem to be getting only one fault , 174 Low Fuel Pressure Delta ???even though pressure at the rail is normal 65 psi??

Ace snake

well , an update :

worked with mechanic today on the damn thing for 4 hours with no progress
changed the map sensor - no effect
switched to other engine runs good
Any ideas ?
Could be a broken spring or gasket ??

unispeed

my 1075 sci had rich idle and rough running
hole in pressure regulator diaphragm was the culprit
fuel that leaks thru the hole travels back the manifold pressure sense line dumping straight into intake manifold
this causes extremely rich conditions at idle and less at speed (depending on the size hole could be worse)

how to check
I just took hose off at manifold and put in container
did a key-up for the 8 sec fuel pump run and if there is fuel coming out the sense line one fuel psi is developed you have a rupture diaphragm

Also plugged sense line or plugged return line causing to high of fuel pressure

57psi for me at key-up then 1lb Manifold pressure change to 1lb of fuel pressure change
idle your fuel pressure should drop form Key-up psi
every lb of boost over atmospheric results in 1 Lb of fuel pressure over Key-up pressure

If sense line is plugged you regulator can't reference your manifold pressure and make changes
also if your return line is plugged you will generally see high presser all the time

hope this helps

Mark

Dirty Socks

thanks Mark for the help , will check and get back to you.

We are narrowing down to a problem with the MAP sensor and connections , the engine is not pulling enough vacuum during idle . even though we tried the sensor from the good engine , it is still a problem.
thanks

Dirty Socks

An Update :

Put on a new map sensor and no change , still runs fine at idle and stumbles and shuts down when putting any load on it.

But a thing i noticed is that all gauges for that motor are flickering as hell.

Can it be the battery ? Where is the main ground for the block on a 42 /700 be ?

Can a bad ground do all this ???

by the way the boat has been in salt water for the past 2 months .so corrosion is an issue obviously .

Thanks

Riley0114

I have hardly any experience with these motors and how they work but I recall a buddy of mine with triple 600 sci's had a bad ground wire on his center motor and it caused that motor to fall on its face and prevent the supercharger from spooling up, so a bad ground wire could be a possibility, sounds electrical though if you have gauges flickering. just my .02 cents, good luck!

4bus

iTrader: (4)

Owning a Gen 7 engine with Guardian mode and no scan tool is going to cost you a ton of money as a DIY'r IMO. Why keep guessing and throwing money at it? Buy a tool from rinda and you we be able to see what is going on, or out of range.

Main grounds on that engine....should be 2-3 large zero gauge ground straps, one to battery, one to ground block on forward bilge and one to the other engine. Secondary grounds can number between 5 and 20, they are all located on the back side of the engine and will attach to ground post on bellhousing along with other areas.

TooLateVTEC

iTrader: (1)

I know it sounds strange, but might be worth trying to take the belt off of the alternator and try it.

Not sure if thats possible or not but if the regulator/s in there go bad, they can give out AC voltage and a lot of ECM's do NOT like that kinda stuff...hence the gauges going crazy and the ECM causing the motor to run rough.

Im not sure if just unhooking the wires from the back of it would work or not as the alternator parts inside would still be turning, but worth a shot.

Dirty Socks

Update : Found it !!!

Checked compression , all good !
Well after checking the electrical system , we discovered a bad battery , changed and and BAM !!
no change !
Took the belt of both superchargers to compare , and we discovered a sheared off drive shaft on the bad motor superchager , so took it off and discovered the pulley was turning and the charger isnt !

Will probably have to order a new one , but very surprised that a super charger can fail at 70 hrs !!!

looks like mercury doesnt sell parts for it ??