Mercruiser 3.0 issues

[Grub54891]

The USGS brought in their boat for repairs, running poorly on both port and stb motors. Determined that there was water/gunk in the fuel, ethanol fuel. Recommended rebuilding carbs, port ran perfect after that. Stb carb When I cleaned it up, had a hole in the bowl, apparently the gunk kept it from leaking. Ordered a new carb from mercury, installed it. The thing won't dial in, I can get the timing at idle set, when given throttle, backfire stumble, quits. Did a basic time a couple times now, still won't run properly.
I think the next step is to swap carbs and see if it helps. just want a second opinion, what else would be the issue,
I did caps and rotors, plug wires are good, and did an ignition module. I was also thinking the coil under the rotor could be going south, but in my experience they either work or they don't.
Engine serial number : 0F 068374
Thank's for any input.

 

[fishrdan]

The thing won't dial in, I can get the timing at idle set, when given throttle, backfire stumble, quits.

Accelerator pump in new carb bad, or need adjustment?

 

[Grub54891]

Good question, didn't think of that. I'll check that tomorrow.
I have heard of fiber timing gears going south, but I doubt that's the issue here, as it all lines up at the setup.

 

[TurtleTamer]

"Did a basic time a couple times now..."

Does that mean that the timing keeps changing or you're otherwise having timing issues? Wondering why you'd repeat that procedure.

 

[Scott Danforth]

AllDodge posted a test procedure for the EST. I believe its in this thread. https://forums.iboats.com/forum/eng...254-97-volvo-penta-5-7l-glplkr-i-o-parts-help

 

[Grub54891]

"Did a basic time a couple times now..."

Does that mean that the timing keeps changing or you're otherwise having timing issues? Wondering why you'd repeat that procedure.

No the timing is not changing, just double checking why it would not run correctly.

 

[Grub54891]

Thanks Scott, I'll check that tomorrow and let ya know how it goes. And thank's Alldodge for the info to.

 

[achris]

Good question, didn't think of that. I'll check that tomorrow.
I have heard of fiber timing gears going south, but I doubt that's the issue here, as it all lines up at the setup.

Automotive cam timing gears are fibre. Mercruiser specify to GM to fit aluminium cam timing gears on their engines. Little bit noisier, but don't strip out like the fibre ones.

Chris. .....

 

[Grub54891]

Interesting achris., I replaced the timing gears on my 1985 3.0, when I did the gasket's and seals. It had the fiber gear, wich had chips out of it, I replaced them with metal ones.

Regardless, an update on the usgs boat,
I had removed the carb to check it over again, Now this was a carb ordered right from mercury, took it apart, found the float level to low, by 3/16 of an inch. And the power valve was .10 thousands smaller than the old carb had. I replaced the valve with the one from the old carb, and adjusted the float. Between the two, it now runs perfect. More than likely it would have been good with just the float adjustment, but I did not want to go back in there again.
And I did test the pickup coil, it came in 800 ohms, well within specs.
Thank's again for the help guy's!

 

[achris]

Interesting achris., I replaced the timing gears on my 1985 3.0, when I did the gasket's and seals. It had the fiber gear, wich had chips out of it, I replaced them with metal ones....

Interesting. I wonder if Merc changed their policy on that. My reference was from my 165, many years ago. In this age of cost-cutting, it wouldn't surprised me. :facepalm: