7.4L merc - low oil -power loss - backfire??

[derekmc1]

I have a 1988 7.4L 454 Mercruiser engine. Rochester Quadra-jet carb. New fuel filters

I was out boating today and the boat was working fine after about 2 hours on the water I was going at idle speed and the motor died on me. It instantly started back up easily. But as I went to take off I had no power what so ever and it back fired a few times and quit. Again re-started easily and I was able to keep it going but with almost no power and a couple more back fires. It soon quit out again. My oil pressure was low when I finally took notice!

I anchored and took off the breather to make sure it wasn?t flooding as it did flood out on me 3 weeks ago but corrected that problem (sticking float).

I noticed that my bilge had oil in it and my dipstick was low. I put in 1 litre which brought it to the full level. After doing this the boat worked fine on my way home!
I have no clue what was going on and am concerned as I am sure something is wrong!

Sorry for the long post please help!
Thanks,

 

[dmarko60]

Re: 7.4L merc - low oil -power loss - backfire??

Same problem happen to me a month back. Same setup 7.4L 454 Merc/Bravo 1. Did a full tune up with ignition plug, wires, coil, cap. I would start with the coil. If that doesn't fix the problem it may be fuel pump (that was my issue) Boat would plane out great, and stumble at high RPMS. If it pops before plane I would lean towards ignition. Try to rev it in netural (No Load) this will determine weather its ignition or fuel delivery. If it pops in netural (ign) if it doesn't I will guess (fuel) Check your fuel/water separator (check for debris) and move your way up to the carb. A trick that worked great to clean the carb. Take off your fuel/water sep, fill it with lucas oil carb cleaner. Let it run from a cool start for 1 min. Let it sit for 15 mins. Run the engine until all the lucas oil burns off.