454 misfire....and oil loss. Why????

[mstang64bb]

I have the original 454 with 686 hours (carb.). It is always maintained. I did a complete tune up, and replaced all cooling lines before her splash this season. I did have an oil leak 2 years ago that turned out to be from the remote oil filter adapter. I replaced those seals as well.
We've had the boat for 4 years, and we only really just cruised in it for short distances at slow speeds.

I took her out yesterday for a fishing trip with a friend. She ran fine all day, making many loops to start back from drifting. We then ventured out further for better fishing grounds.
On the way back about 1/2 in she started to backfire. Once every couple of minutes. I was at 3000RPM, never had a loss in power and all gages were fine. I thought perhaps she just needed a good blow out as she doesn't ever go this fast.
I got back into the channel at about 1100RPM and she was running a little rough...sporadically, but no misfires. We made into the slip. When I open the engine cover I discovered there was oil in the bottom of the bilge, not quite enough for the pump to eject...yet. In the slip, she did idle ok, not great, but ok.
Being a little frustrated and upset. I left it for today as the engine was still to hot for me to start climbing over.

I'm guessing I need to check the remote oil filter seals again. But other than that, I am at a total loss on where to start, or what to do. I'm afraid I may be out for the season and will need to look at getting a replacement engine. I cannot understand what would cause the motor to backfire once in a while and the oil loss..

I am asking for help and some suggestions as to where I should start and what to look for?

Thanks,
Bob

 

[Crushin It]

Sorry to hear this. I would first check your oil level in engine to determine just how low it is. If you had any water in bilge even a little oil can make it look like a lot. Not sure about your back firing. Good luck.

 

[PlayDate]

Might be a couple of problems. The backfire could be bad gas or it could be mechanical. I would probably start with a compression check given the number of hours on the engine. That will tell you whether a more serious problem exists. What did you replace on the "complete tuneup" and what is the story with the exhaust manifolds?

The oil leak is likely something else. It shouldn't be hard to find where it is coming from.

 

[hottoddie]

The oil loss and backfire may or may not be related. Do you have fresh water cooling?

 

[mstang64bb]

Well, I dodged a bullet. :smt001. It turned out that I needed to replace my ignition coil. The engine oil is full, and the oil that I thought was in the bilge is just a film over some standing water from the rain we had the night before..... Whew!!!