QUIKDECISION

Offthefront,
I would agree with coolcarwrench, pull the plugs to see if one or more appear to have discoloration that is different from the others. If you are using a synthetic oil, it may difficult to read that on the plugs. Also, check to be sure that your fuel pump ( I am assuming you have a mechanical type ) is well secured to the block and that you have no oil leaks around it.
Do you notice any deposits around the port exhaust that you don't see on the starboard engine? If all 8 plugs in the port engine have the same general appearance, how do they compare to the starboard engine? This latter statement may not be a valid comparison if the engines are not the same age... Did you determine the cause of your overheating issue?
Backfiring can be caused by variety of items. You may have nailed it already.
A faulty carburetor... dirty clogged etc. could cause a lean condition that may lead to backfiring/overheating. Advanced timing could also cause a smilier problem... Since you pulled the top end off, it is likely that any timing issues would have been resolved. If this is all redundant, my apologies...
I would be curious to know what you do find...
Doug

US1 Fountain

Would a motor even run if it was burning this much oil? How do the plugs look?


edit, just seen your update post.

offthefront

The Backfire problem seemed to go away with new plugs ..new fuel filters.. a merc fuel additive and a Quart of MMO .... I do need to check the plugs but it does have Mobile 1 ... There are NO external oil leaks ( i assume your refering to external leak on fuel pump?) The Exhuast dumps ino Silent thunder box and all four exhaust are tied together(common area in box). a merc mechanic I know wants me to go back to merc oil .... I will post what I find ... just with the bad weather and winter having been putting much effort into solving the problem ..

offthefront

thats the one thing that kills me .. it looses about 1 quart per 2 hours ...but runs fine ...both motors turn same RPM at all speeds ....idles fine....Cranked it last saturday ...(5th) ...and it had been since about feb 9th .... it fired right up ...didnt touch the throttle .....

offthefront

Update on oil thirsty motor .... I pulled the outlet water hose from the oil cooler today ...didn't really see any signs of oil .. I put 20lbs of pressure on the oil cooler and it dropped about 1lb in an hour. I have the hoses pressurized so could be some leakage at hose clamps .....I did check for PCV valves and apparently 454mags don't have em ...just a straight shot from Valve cover to Spark arrestor. A merc Mechanic I know wants me to bypass the oil cooler and try that .... sez pressure test isn't a sure thing and that cooler could leak after it gets hot ... looks like a major deal to remove oil lines and tie them together ...any thoughts on just bypassing the the water around the cooler ? then if any oil escaped in the cooler it would dribble out the end ?

formula31

That should work fine if you have an oil temp gauge. Just dont let the oil get over 250. If you dont have an oil temp gauge, just keep your wot down to a few short blasts.

KNOT-RIGHT

This would eliminate the cooler. Try it....
Insptech mentioned this procedure above.
If this fails atleast its a easy repair.
Read plugs they will tell you alot.


Good luck
Gerry

offthefront

Thanks for the info on the oil temp ....I dont have one .... was thinking about stickin one in so I could watch the temp ....can you put a sensor on one of the ports at the remote oil filter ? what would be normal temp ?

Thunderstruck

I would pull a breather with the motor running and see if there are strong pulses of gas coming out of the breather i.e. blowby past the rings. The dipstick pushing out is undoubtedly caused by crankcase pressure from blowby. Check the breather tubes/intake for oil, blowby pushes more oil out of the breathers into the intake system. Sounds like you have a broke motor. Look at the oil cooler last, you know the motor was over heated which can produce the symptoms you have. Stay with mechanical issues around that.