5.0 ltr mercruiser EFI 1999

[stevco]

for 3 years my engine starts backfiring & tack goes nuts when cruising abround 3200 rpm. I have replaced plugs, dist. cap, rotor & still happens. Took it to Mercruiser mechanic 4 times, he could not find the problem. I then put a new s/r tachometer on, still same problem, I feel unsafe on the water as I am in the middle of no-where up the BC coast. I am into this for over $2000 now, need some advise.. I have been reading up on this & I keep pulling up "shift interrupt switch" I suggested this to the mechanic & he disagreed. Has anyone had this problem.? I need a new mechanic too.!

 

[Espos4]

Do you have an alpha outdrive? Then yes you have a shift interrupt switch.

You should be able to bypass it for testing purposes and take it for a test drive to see if it helps.

 

[scoflaw]

Pickup coil in the dist. can be problematic. What happens above and below 3200 ? Compression good ? How did this get to $2000 ? What else has he eliminated ? Good fuel pressure ?

 

[stevco]

Yes I have a Alpha outdrive, saw a video from someone with same problem on s/r club. My problem is identical. Have not checked fuel pressure or compression, below 3200 rpm runs somewhat ok around 1500. It got up to $2000 for all the electrical work, driving the boat around trying to find problem. Twice the mechanic took the boat out, gave it back to me & said it's running fine, nothing wrong with it... I get in & within 15 min. It starts spluttering & backfiring. This mechanic is a Mercruiser dealer. I hope it's the shift switch cause I just ordered it comes with a new bracket apparently $240.

 

[scoflaw]

There are methods for testing these components before you lay down the cash. All you had to do was jumper the 2 wires together for the shift switch test.

 

[stevco]

thanks scoflaw, I may well n go do this.
Thanks so much.

 

[Bt Doctur]

do you know how to hot wire the motor?

 

[stevco]

No I don't , sorry