Rebuilt engine install, needs some trouble shooting advice

[brushmore]

I have just about finished my restoration on my 1999 Challenger 1800 and had both engines rebuilt by Full Bore. Yesterday I did a quick test before I went out on the water. Port engine has no problems and is starting right up. However, the starboard engine did fire up once and ran for few seconds. Then I went try to run a bit longer and connect a hose to check for cooling system leaks once it fired up again. But it will not fire up again whatsoever. I even tried spraying some starting fluid but not even a cough out of it.

So far I have:

-Pulled the plugs, and did not note anything unusual. Even cranked it with a plug out and sure enough a mist of oily gas shot out over the port side.
-Verified I have spark with an inline test light
-Fuel pump is pumping fuel and I am seeing fuel come out of the return line.

I need some advice on what to trouble shoot next. I seem to have fuel and I seem to have spark. What do I check for next?

 

[Chris conx]

I'm not an expert but I would check compression
Three main ingredients
Spark
Fuel
Compression

 

[JeremyD615]

You need to pull both plugs out of that motor and crank it until that oily mist stops coming out of the motor. Then put a few drops of premix down in the plug holes, install new or cleaned spark plugs, and try it again. The engine is fuel flooded, and when the plugs get wet they won’t fire...

 

[brushmore]

An update. Since the carbs were rebuilt with non Mikuni parts, I redid them the right way. In the process I noticed I missed that the return orifice on the PTO carb was plugged. This was one of my problems.

With the rebuilt carbs still no luck but I think @JeremyD615 is on to something. At first it would start to fire but not stay running. Then I got to point where it was flooded and not catch anymore. I am thinking I have a carb issue still so I am going to try it with the carbs from the port side since I know they work fine.