Mercuiser 260 TBI WTF?

[fixpc4you]

I Need help on my 1999 stingray 5.7 Mercruiser through hull exhaust tbi injection motor #L093630. I can run all day WOT at 65 mph 5K rpm no problem. about 30 minutes after I slow down to 35 mph and cruise the lake the engine starts to pop and backfire and progresses worse until total shutdown. At that point I have to wait for about 10 mins or so and then everyting is fine. I have replaced plugs,wires,dist cap,button,coil, ignition module,distributor,fuel pump,fuel-water seperator and the only thing I have gained is several miles an hour! Now the really important thing that I notice when it starts it's pop and backfiring routine is the tach will jump all over the place from 1300 rpm to 5k and the motor is truly turning close to 1300. Can anyone help?

 

[newport dave]

Re: Mercuiser 260 TBI WTF?

When you installed the new ignition module did you put thermal transfer compound on the bottom? If not, you could be having an ignition module overheat. The symptoms you describe are consistant with module overheat.<br /><br />Dave

 

[fixpc4you]

Re: Mercuiser 260 TBI WTF?

Yes I did put the compound "grease" on the module and even then the problem existed before the module change.

 

[Don S]

Re: Mercuiser 260 TBI WTF?

Try it one time with the engine cover open. May just get to hot due to lack of air flow, might help to just turn on the bilge blower to help circulate the air to cool things off.

 

[fixpc4you]

Re: Mercuiser 260 TBI WTF?

We have already tried this.. we had the cover off when we were trying to troubleshoot the issue the first few days. It took as long as usual but still starting missing and backfiring around 3 to 35k