Somewhat new 270 with distributor or spark problem

"I have a pair of 2.5 year old

"I have a pair of 2.5 year old crusaders (270 hp, 350 CU IN blocks). On the starboard engine, the rpms are going up and down on the tach (tach is bouncing), the engine has lost about 90% of its power and it backfires. It happens intermittently. It is rock solid and I can cruse normal (about 3500 rpm)then goes into this mode. When the tach is bouncing, the engine is not really changing the rpm, just the tach…can't get the engine over about 2000 rpms, actual. Also, the base of the distributor itself is very hot to the touch with the engine off (unlike the good engine, which has a warm...not hot distributor). Same thing happened last year, but the engine finally died completely and the dealer replace the distributor assembly. Worked fine for about 150 engine hrs. What is up? Any ideas? In addition to fixing the problem, I go offshore fishing and need the reliability."

"Steve,

I would have that d

"Steve,

I would have that distributor pulled and looked at. Heat is a byproduct of friction. It is possible that there is a bad bushing in the distributor. Have the cam retard checked as well. Cam retard is set by rotating the distributor just the way you used to set the ignition timing. If the cam retard is off it will cause the engine to run rough, this may engage the knock sensors which will reduce the engine RPMs. (I'm assuming this is EFI) It is also possible that the module in the distributor is failing, causing both the heat and running problems.

Good luck
Rick"

"Rick,
Engines are 2004 5.7

"Rick,
Engines are 2004 5.7 ltr. with Carburetors , No EFI, 270 hp, and I don’t believe they have an anti-knock sensor.

The motor runs fine, then goes into is mode were the tach is bouncing all over but the engine is in a steady decline of power, running rough and occasionally backfiring. So I am suspecting there are extra ignition sparks or random timing advance which would make the tach bounce. It then sometimes snaps out of this mode and runs fine, which really makes me wonder what is going on.
There was a noise that sounded metallic when in the bad mode, but not all the time. It would come and go. Sounded like two metals rubbing each other. My friend described the sound as like a dry barring. So maybe the distributor barring is giving, but would that cause the timing to jump around?

The dealer replaced the distributor last year. Could the same thing, what ever happened, happened again? I don’t want to blow the engines, pre-detonation is bad.

Any guesses what this failure is and why it has happened twice?"

"Steve,

Distributors don&#3

"Steve,

Distributors don't really go bad, especially in such a short time. If there is a bushing going bad in the distributor, it could be caused by a casting problem in the block or intake manifold. Also, when the engine acts up, disconnect the tachometer. It is possible for a bad tach to short out the ignition system."