Do as topgun3690 says.
Check compression, spark at all three cylinders with a spark tester.
The spark should jump 3/8 in or more in atmosphere.
Clean the carbs and set the float level if necessary.
Check and I would suggest you to change the fuel pump diaphragm.
They are cheap and they will go...
Check the gaskets at the exhaust cover, BUT be careful the bolts can snap really easy.
If they are hard to loosen penetrate with penetrating oil, heat them with a propane torch and tap them with a hammer.
Move them back and forth with small steps.
The Force power when I think about it that 120Hp power head I bought in a package was for a jet-drive and not a L-drive.
Maybe I am wrong about the 125Hp power head not fit to the L-drive drive shaft.
FYI guys
A few years ago I parted out a 120Hp L-drive power head that was blown.
It had the Mercury Thunderbolt ignition system (not CDM typ).
The funny thing with this one IT HAD AUTOMATIC OIL INJECTION.
The oil pump was driven from a gear that was integrated in the crank shaft.
The gear was...
Bad connections at the battery will cause the 12V to drop low and if the power to the ignition drops the ignition system would not work.
Newer ignition systems that are self energizing does not affect if the 12V drops but if the starter do not turn with good RPMs.
That is why it is important to...
As topgun3690 says use TC-W3 two stroke oil.
There are other two stroke oils for air cooled two strokers.
TC-W3 (two stroke water cooled) run at cooler temperatures and TC-W3 oil produce less smoke.
Two stroke oils for air cooled engines leave more carbon in the exhaust ports and it maybe build...
#Jiggz, no I am saying that the diagram you posted i #10 is wrong but the one you posted in #13 is right.
If he will troubleshooting he has to use the diagram for the Prestolite system and I imagine he will figure it out then.
The head of this thread says 1996 120Hp Force Mercury and as it is a...
Well the concept and thought was good BUT then the customer and boat owners was new to the boating, similar to Force outboard as a package with Bayliner boats.
Cheap stepp in boating and no know how in maintenance.
As I am from Sweden and Volvo Penta introduced the Aquamatic in/out drive in mid...
First check the compression in all cylinders.
If low or no compression in bottom cylinder you have a bad head gasket.
To pull the exhaust cover and check the gasket can be a PIA.
The bolts that holds the cover can snap really easy and you have to drill them out and retap the threads.
Looks like this is a power head to a L-drive.
You can see back fire through exhaust manifold tube that are for the L-drive power head units.
Do as The Force Power suggest, do the link and sync.
To test an ignition coil you need a spark tester with a adjustable gap.
The coil should jumpa a spark for 3/8 in or more in atmosphere.
But there can be other issues that cause no spark if you check with the coil connected to the engine.
To be really sure you have to test with a coil tester at...
You can make that gasket 47-F286555 for the lower split of the gear case by your self.
Get some gasket paper and cut it out .
When assembling it coat the gasket with a thin amount of some liquid gasket such as "Permatex Avaition form a gasket" or equal.
Do not use a thick gasket paper...
As topgun3690 says, the water level need to be above the water impeller housing.
The impeller is not self priming, it need to bee submerge.
Water level need to be at least 1 in above the top of the impeller housing, 4-5 in above the split line of the gear case.
Regarding running with muffs.
Are...
The rectifier/regulator can interfere and make the ignition system to act confusing and fail.
Outboardignitiondotcom has troubleshooting chart, go through that chart and check out with your engine.
When I mention magneto I was meaning the trigger ring that moves to advance the timing. I use the wrong word that was why I changed to trigger ring.
I suppose your engine has the Prestolite ignition system with 2 CDI boxes (blue or black) and 4 ignition coils.
I would suggest you to disconnect...
