SROC experts, I posted this on...

[FIG]

SROC experts, I posted this on CSR forums. Looking for help. 

Need some help:

After splashing the boat and during my first short drive from storage location to marine slip I had a Smartcraft Message on SB engine.

- Smartcraft read: STBD System Fault with a a message that read “Fuel Sender”. The followed message once you hit “more” read - Fuel Level Sensor is not working properly”.

- Assuming it was just the fuel sender unit, I went out for a quick ride and had what I describe as RPM roll-back. While cruising at 3850 per/engine, my STBD engine slowly rolled back. Immediately shut it down, check the engine (s) and nothing noticeable. Everything looks good (oil, water, no leaks, etc). All engine indications in the digital and analog indicators were normal, other than now that fuel gauge reads zero.

- So come back and decide to go out another day to verify. This time while “trolling” at idle, my Port engine went from about 700 RPM to about 480 when I shut it off (luckily I was looking at the dials). Inspect engine(s) and nothing. Restart, got and to fuel dock. My intent was to fill up to 75%, however due to erroneous indications in fuel sender, ended up filling the SB tank. After this we headed back to marina and everything look and felt normal (headed back at 4200ish RPM with no issues), then cruised at idle to dock with no issues.

- Replaced fuel filters on both engines, and fuel filter for gender (this is the only I can see/find/per manual on my boat).

- I would expect this to happen on one engine, but the roll back on Port got me a bit concerned.

- I have researched this with potential issues on fuel sender units, etc... but haven’t found an answer.

- checked plugs and look good, but I’ll replace the anyways.

The boat has 380ish hours, Twin 350 (MIE 350 MAG MOI HORIZON) V-Drives.

Fuel Tanks made by Florida Marine Tanks (FMT-94S-SR, P/N 1818823, 94 gals on SB & FMT-107P-SR, P/N 1818822, 107 gals on Port)

In addition I will replace all spark plugs, wires, and anything needed.

Current plugs are NGK ITR4A15 (however on label side of engine it recommends AC 41-932). Which one anyone recommends?

Recently I discovered my Idle could be a bit high. After IAC replacement my Idle has been in the 700+ (sometime as high as 770-790). The same label on side of engine indicates that Idle RPM should be 600 Non Adj. Not sure what’s going on here. Disconnected throttle cables to verify it wasn’t the cables and still in the 700 RPM range.

I have babied this boat since I bought it slightly used with 179hrs. This is the first time I have had any issues.

Sorry for the long post, but if you have gone through something similar please chime-in. I maybe missing something simple.

Thanks in Advanced!

FIG

[wingless]

As always, start w/ the basics: try operation w/ Ethanol-free fuel; verify fuel tank vent unobstructed; both the hull fuel filters and the engine fuel filters are replaced. Ensure the internal water passages in the exhaust system are not corroded, causing excessive temperatures. Ensure the raw water pump and impeller are not partially failed. Ensure fragments from a previously failed raw water impeller are not obstructing that water path, likely resting against the input to the first cooler, probably for the transmission.

The most important tool for diagnostics on this type of problem is a fuel pressure gauge. It has a dial w/ a pointer, a short rubber hose and a screw on Schrader fitting for connection to the fuel rail valve. Check pressure when starting and during the problem.

Using the correct Factory Service Manual (FSM) for your engine, use a handheld vacuum pump to verify proper reaction to applied vacuum on the fuel pressure, according to the FSM.

Note that heat / temperature can be a BIG factor for proper fuel system operation.

When I operated in New England I had ZERO fuel issues. When I operate in the tropics I had LOTS of fuel issues, until I designed, fabricated and installed a custom thermostatically controlled heat extraction system. Now mine operates problem free.

[wingless]

Here is a link, probably showing the parts for your engine.

As-always, ensure the parts are correct using the engine serial number.

https://www.mercruiserparts.com/bam/subassembly/31599/12841/50

[FIG]

Wingless - thanks for the advice. I haven’t done the fuel pressure check. I’m fairly handy, need to learn how to do it.

Didn’t do much, because after replacing spark plugs, both impellers and wear plates (Port was getting stuck for some reason), new fuel filters on cool unit everything seemed fine for a few days until yesterday. At WOT Port Engine reached 4600 RPM, SB only 4200 RPM (normal for WOT 4500-5000). 1/2 tanks of fuel.
In addition as mentioned on another site, my SB engine consumes about 2GPH more than the Port, has anyone seen that?

As always - THANKS - for any inputs.

[wingless]

YW

The fuel rail has a Schrader valve for the screw on fuel pressure gauge. Has that been tested per the correct Factory Service Manual (FSM)? It would be good to check during normal operation, then when problematic.

The "easy" first step is to eliminate the thermal effect on fuel.

When the engine(s) operation fails can the operation be safely verified with the engine compartment lid open, to permit release of the trapped heat?

Have the exhausts been verified to be acceptable, first by confirming it is possible to continuously hand hold the exhaust exterior while the engine is operating? A good second step for raw water cooled exhaust parts is an annual disassembly to verify that the internal passages are acceptable, w/o excessive corrosion and that there is sufficient SOLID wall thickness between raw water and exhaust passages.

The gauge reading difference of 2GPH between engines might just be an instrumentation error. Is that confirmed by topping off fuel tanks and comparing consumption by the dock fuel pump? If so, then this may be indicative of many unrelated problems. The best action is to ensure the engines and transmissions are operating completely properly and that all the running gear are at 100% terrific condition.

[FIG]

Update: so after tons of research and help for this groups and Club SR, I had two separate problems. On SB engine was a fuel sender unit I was able to pull out, empty the fuel, test and re-install. So far so good. I’m sure at some point will have to replace.
On Port Engine, had to replace the Cool Fuel Unit. On mine the cooling chamber (raw water in, then out) was slightly corroded. When cool and at a higher fuel flow, everything would work fine. However, after running at normal cruise, then coming back to either idle or near idle, the Cool Fuel Unit will heat up, preventing proper fuel flow to the engine, making it stall.
Well friends - $1279 later and about 4-5 hours of good labor, the pump has been replaced. There’s not a lot of room on the SB side to work with. Be careful when pulling the fuel line, mine was fairly stuck in there. Slowly and carefully was able to do it.

Thanks for the tips!
Salud!