STUMPED: intermittent bogging..

[KennyCarkeet]

I purchased a 2006 SV211 from a storage yard (who purchased it from a family moving across the country.). The boat has had a motor swap to a GM Vortec 5.7.

since I purchased the boat has intermittently bogged down to nearly an idle. It’s inconsistent; could run fine for 20 minutes or 2 minutes. When it bogs, all I have to do it idle for 30 seconds then she’s fine again.

so far I’ve replaced: cap, rotor, both fuel pumps, coil, fuel sending unit. The old fuel sending units black rubber magnet had half disintegrated into the tank. I took a magnet and got as much of it out as I could.

yesterday I tested fuel pressure. Both pre-bog and during bog I get about 70psi.

i “removed” perfect pass but snipping the grey wire and pulling the terminal plug to motor.

Thousands of dollars and tons of hours later I’m stumped.

anyone have any ideas? Thank you so much!

[SilentSeven]

Just a couple of random thoughts.

Does this engine have an OBD2 port that you can use to pull codes?

You mention parts of the fuel sender disintegrating in the tank. I wonder if you have a fuel delivery obstruction issue that's impeding flow volume. Sort of like this - some odd bit in the fuel pickup or fuel line is loose. When running under load, the fuel volume is sufficient to pull the bit into the line reducing available volume. Engine bogs. When you idle the engine, the volume requirements decrease and the bit floats out of it's obstructing position and you're good to go again. Not 100% sure this aligns with your observation of no change in FP. Still, I'd consider inspecting/replacing all the fuel filters and also look at blowing compressed air from the engine side fuel connection back into the fuel tank to try to unblock the line.

[Tom_H]

You may want to check the fuel pressure specs, 70 sounds a bit high to me. I would think 40ish would be correct. Is there a fuel pressure regulator in the loop, or possibly the return line to the tank is plugged (too much fuel could cause bogging). I would probably check and/or replace all the fuel lines too. If the lining of a fuel line is delaminating, it can cause really odd symptoms like intermittent fuel restrictions, but I would expect to see fuel pressure changes in that scenario.

Any chance you have water in the fuel? If you have a fuel/water separator, dump it out and watch for separation (and see if any debris pours out).

[jpwhit]

If the boat has a non-PCM engine, then you need to describe the topology of the fuel system. I'm assuming the boat doesn't have the original fuel system layout which would be

tank pickup with check-valve->inline fuel filter->low pressure pump->PCM FCC->Inject fuel rail->fuel rail mounted pressure regulator->fuel return hose to tank.

What's the actual fuel system topology of the boat now with the engine transplant?

What ECM does the engine have?

Who was the engine Marinizer?

[KennyCarkeet]

Hey everyone! Thank you so much for your input! I'm attaching a few photos of the motor. I'm sorry I dont have all the answers!

Regarding fuel lines, replacing them seems like a good idea anyways. I did remove the fuel and vent hose and blew through them and they seemed to have no blockage. I pulled out the pickup line and it seems almost new. Clean with the screen at the bottom. I haven't checked the return hose yet.

When i first got the boat I took it to At The Helm Marine in Castaic CA where they did an overall service which included the Cap/rotor etc, as well as a new fuel filter.

JPWhit - I hope you get some of those answers by seeing the motor. Please let me know if you need different photos. Your guys' help is very appreciated.

[KennyCarkeet]

Hi again. Here is the fuel setup. Really hoping anyone has more ideas! Thank you!

[KennyCarkeet]

Should there be a hose here, I see fuel pickup line, 2 fill lines, and one vent line. (And fuel sending unit.). Am I missing some sort of return? Any chance this can cause my bogging issue?

[jpwhit]

JPWhit - I hope you get some of those answers by seeing the motor. Please let me know if you need different photos. Your guys' help is very appreciated.

It's not practical for me to figure out the fuel system topology from pictures. You would need to trace the fuel hoses and other components and identify all the fuel pickups, valves, filters, pumps, regulators, etc in the order that the fuel flows. You'll likely have to take some stuff apart to accomplish that. If that's not something you're comfortable doing, then you probably need to find a really good marine mechanic. Making an engine work well in a boat that's different from what it was intended, takes a pretty high level of skill and experience.

Nobody can answer the question in your last post about that extra fuel connection on the tank without knowing the fuel system topology and the type of regulator(s) in the system.

[KennyCarkeet]

Thanks!

besides fuel, I’ve seen some things regarding voltage regulation that can cause bogging. Potential alternator replace?