50 TLDI will not start, runs on 2 cylinders only

[Zoran]

I have Tohatsu 50TLDI, 2008, worked like a charm until last 3 weeks.

I had problem on my 10 day trip with when the engine will with no apparent reason drop the RPM for a second and then come back. This was repeated every 5-30 minutes regardless of RPM (happened on WOT as well as on cruising speed around 2400 RPM). I changed the spark plugs and it kind of worked happier but the issue was still there. Last Thursday when I sail out it started loosing power if I am under 2000 rpm (RPM will go at least 400 up and down all the time) but sort of hold it if I am over 2000. It finally decided not to start next day on my trip home. After many attempts I manage to start it. It was running rough and would not go over 2000 RPM even at WOT. All the time I could smell gasoline in the exhaust. I made it to the marina and when I parked the boat on the trailer once I tilted engine down (I always leave it in the upright position) a black water, mixed with gasoline and oil came out of the exhaust in the propeller.
This morning I pulled spark plugs out and one on the lowest cylinder was showing that this cylinder was not firing at all (plug was oily and wet). I cleaned the spark plugs put them back, try to start it but without success. It makes a sound as it is almost starting but will not. I had no more time today to look at it but I would like to give it another attempt tomorrow. Any ideas what should I look for?

Thank you all

[seahouse]

A general (I'm not at all familiar with TLDI) way to confirm the plug is not firing is to take out the plug, reconnect it to the plug wire, ground the body of the plug (away from the open cylinder), and have someone briefly burl the starter and see if it sparks. Know that, in rare instances, a plug will spark for this test, and not spark under the conditions of a pressurized cylinder.
If it doesn't spark, could be the plug (but you did put new ones in), the wire, or something further up the ignition system. The wire is the next easiest to repair. You can also do a visual inspection for carbon tracking or overheated or corroded parts, but after that, I bow to the the next posters, because I know squat about the Tohatsu ignition.

[Catigale]

It sounds like injection issues to me Zoran. Changing the plugs was smart, but if the motor is an 2008 I doubt anything electrical has gone wrong. Plug wires maybe? Check all wiring for signs of corrosion?

[raycarlson]

start with pulling any stored DTC codes from your computer,if there's no stored codes i would also start with bad plug wire

[Zoran]

I do not have service manual so it looks like I will have to take it to a dealer. PITA as I do not have street tow vehicle and I will have to borrow a truck and take day off work to do it
Thanks for help

[aya16]

By checking the spark you could save yourself some time and money. If there is no spark then check all the leads to the spark plug as well as the coil wires.
next if no spark and all the leads (wires) are ok, swap coils from another cylinder, if that works and you get spark, your coil is may be bad. Make sure when you swap the coil
you also use the wires going to the bad cyl. This will make sure that the coil is getting proper voltage to work. In other words, if the swapped coil with the og wires begins to spark
its the coil. Double check by putting the og non spark coil on another cyl. If it doesn't work (spark) its the coil, and needs to be replaced.

But first make sure all spark plugs get spark, swap the coil with one you know works.

mike

[Zoran]

I went back to it yesterday and it started on first attempt but it is running very rough, shaky and noisy. I tried do add more throttle (accelerate) and the motor will either shut down or slowly start getting to higher RPM-s but it is very loud, missing and smoking. I tried removing coil from each plug and it will not start at all, which is telling me that all three are working now but definitely not good and not the way they supposed.

[Boblee]

Is it possible the TLDI has the same engine protection setup as an etec that allows it to shut down to safe revs when an alarm comes up so that it can continue running at reduced revs for a limited period?