4.3 Mercruiser TBI

[ziggy]

Motor was running fine last week but today I headed out and couldn’t get past 2500 rpm. As soon as I gave her, more throttle she started bucking and wanting to stall. Only thing done since last week was addition of a bit more fuel, so tried to check the vent line ( history of burping), so tried blowing the line out.
Also noticed the temp gauge seemed stuck at 100 degrees so not sure if that’s related. Anyway, any ideas while I wait to see if I can get a mechanic down to her. Horrible time to crap out

 

[SpringVelocity]

Lame. Know what that is like. If is bucking an dieseling at 2500 rpm not advancing/stall that is sign of the Electronic ignition module crapping out (common Mercruiser issue). It can also be simply your distributor cap. That is easy to fix to do yourself.

As far as your temp could be issue with thermostat. You could replace it.

 

[ab1752]

Tbi? Have a good hard look at the spray pattern for the throttle body injectors. I went through this recently and it was an epic pita to sort out. TJ17 from standard auto are the injectors for the 5.7 vortec VP, I bet yours may be the same. They are rated at 60 lbs an hr. Is it running rich, as in are you noticing black smoke or soot across the transom?

Also if you can confirm fuel pressure high and low that would be good. It's something like 30 psi high side and 10 ish low as memory serves.

Also check distributor, wires and plugs. But this sounds an awful lot like injectors and i was able to get mine via north shore parts.

 

[wildmanyeah]

Yeah that’ll be about a thousand

 

[ziggy]

Tbi? Have a good hard look at the spray pattern for the throttle body injectors. I went through this recently and it was an epic pita to sort out. TJ17 from standard auto are the injectors for the 5.7 vortec VP, I bet yours may be the same. They are rated at 60 lbs an hr. Is it running rich, as in are you noticing black smoke or soot across the transom?

Also if you can confirm fuel pressure high and low that would be good. It's something like 30 psi high side and 10 ish low as memory serves.

Also check distributor, wires and plugs. But this sounds an awful lot like injectors and i was able to get mine via north shore parts.

The injectors should be good the whole throttle body was rebuilt a couple of years ago ( cost a grande and was done by a guy in Texas if memory serves) when one of my three new engines were installed by Vector (two were on warranty). Will check the wires and distributor. Thanks for the input.

 

[ab1752]

The injectors should be good the whole throttle body was rebuilt a couple of years ago ( cost a grande and was done by a guy in Texas if memory serves) when one of my three new engines were installed by Vector (two were on warranty). Will check the wires and distributor. Thanks for the input.

Right on, just remove the flame arrestor, and fire it up, the spray patterns would be invented V and even. If you don't have black smoke or evidence of it running rich, and the spark checks out, I'd head towards fuel pumps. Don't laugh but Google mancave mechanic...Troy knows what's up for sure and I have a set of his pumps in our boat with my old ones as backup. Do you have a fuel pressure tester?

Where abouts is the boat located?

 

[ziggy]

Well as an update it turns out the distributor was the problem. Had a mechanic install it but he’s having trouble timing it. Seems it requires a special tool called Volvo Penta Timing Shunt tool. Hopefully she’ll be running well soon. Changing the distributor took me from 8 KTs to 19. Still a long way from previous high end.

 

[SpringVelocity]

Yeah mercrusier has shunt as well as part of timing process. All it was was little pigtail thing.