'78 175 Mercury

[cookyi]

Please help, this is driving me nuts!:facepalm:
My 175 V6 Mercury will not rev out when in gear and keeps fouling #1 spark plug. It revs fine when in neutral.
The compression was a little low on the starboard cylinders so I replaced the head gasket - no difference to the running problem.
I stripped and cleaned the top carb. Nothing looked bad and again, no difference.
The plug is not wet but gets really black with soot.
I'm thinking reed valve next.
Any suggestions would be much appreciated.
Many thanks.

 

[cookyi]

Re: '78 175 Mercury

Sorry, also wanted to know whether I should replace the idle stabilizer unit which has been removed from my engine?
Thanks

 

[Maxz695]

Re: '78 175 Mercury

View attachment 92096View attachment 92097View attachment 92098did you do just the headgasket I found damage in my exhast port inner plate and it was letting water into my exhaust making the engine misfire when coming off plane I repaird it did all gaskets on the powerhead and shes fine now. Also note the carbon buildup. This will turn the plug black. Mine is a 2 stroke but the 4 stroke valves may also be letting water in by bad gasket or a similar plate

 

[Faztbullet]

Re: '78 175 Mercury

Your 175 is the 2.0 liter block with "hemi" heads and compression should be about 120 psi per cylinder. Black sooty plugs is usually excessively rich from: improper float height or ethanol damaged float(heavy),inlet needle not seating, improper air metering jet, low compression/weak spark on that cylinder causing incomplete combustion. This can be from: defective switch box, coil not grounded properly (problem on early models with orange coils) or weak stator output which usually affects more than one cylinder.

 

[cookyi]

Re: '78 175 Mercury

Guys, PLEASE PLEASE HELP!!!!!
Still havent't sorted this.
With the motor running & using a strobe light #1 cylinder doesn't spark anywhere near TDC (I can't even see the flywheel sticker). When I pull #1 plug cap it's clear it isn't firing at the right time (no change to running).
The flywheel TDC markings line up with TDC on #1 cylinder on static check. All wiring from the stator & pick up to teh switch boxes and coils is correct and all plugs have a healthy spark (just at the wrong time!).
The stator looks to be after market and is part no. 398-5454A6. Crowley marine & others show the part number as 398-5454A7. Before I buy a replecement, is this likely to be the problem?
The motor runs like a dog & I'm missing the good weather. PLEASE PLEASE, any suggestions will be grayefully received. Thanks.

 

[j_martin]

Re: '78 175 Mercury

Cut out the crying, for gosh sake. You've been fighting this problem for awhile. You brought it here in the wee hours of this morning, and you've already started 2 threads on it. BTW, delete the other thread please.

Here's what I responded to the other thread. It may help, but it looks like Fazt has the same info and more experience:

Stator location should have no effect on timing. That is generated by the trigger. All the stator does is charge up the capacitors in the switchboxes.

I see you're using a non standard procedure for checking the timing pointer location, so I have to ask these questions.

Has the flywheel been disassembled at the flex plate?
Are you sure you're on #1 and not #2?
Are you sure compression is good on all cylinders?
Are you sure the trigger wiring is right? (Hint, use incandescent lighting to view colors)
Have you ohmed the trigger, specifically looking for grounded or cross connected coils?

The A6 and A7 9 amp stators are interchangeable, but the odds that is the bad part are close to nil.

Once we establish a base line, we can get to the answer with just a few more relatively simple steps.

hope it helps
John

 

[cookyi]

Re: '78 175 Mercury

:facepalm::facepalm::facepalm: