Hi y'all, We have 2006 320 Sundancer...

[garkov]

Hi y'all, We have  2006 320 Sundancer with 350 MPI Horizon engines.  Starboard engine stalls out slowly after running for 60 - 90 minutes.  Fuel rail pressure drops from ~45psi down to 10 psi then 5 psi and stalls out slowly (takes 30 - 60 seconds to stall out).  Engine will restart after sitting about 60 minutes and run normally for about another 60 minutes when it stalls out again repeating the process.

ECM diagnostic check showed no electrical faults/codes.  Need help diagnosing the root cause.  Looks like it could be a fuel pump issue.. is there a way to confirm if it is a fuel pump issue?  Hate to spend thousands on a new fuel pump module without confirming that that is the problem.  Has anyone experienced this and solved it?

We run non-ethanol fuel only, have new fuel filters, 280 hrs on engines and well maintained. Looks like the original fuel pump modules but difficult to confirm.  Help!!

[wingless]

The fuel pump gauge is an essential tool for understanding then resolving problems like this.

It has a short flexible hose attached to a dial indicator and a Schrader valve that screws onto the fuel rail fitting.

The engine will not run / start w/o sufficient fuel pressure.

It may be vapor lock causing the problem. If so the source must be identified and resolved.

Is it possible to continuously hand hold the exhaust elbow while the engine is running? If not, then the internal raw water passages may have excessive corrosion.

[wingless]

Here is the Mercury 2009-01 Service Bulletin.

https://www.mercruiserparts.com/bulletins/001/04/2009/en_01.pdf

It may be that Mercury will provide past-warranty assistance because of this defect. Contact them to see if they will help.

[garkov]

Thanks Wingless, Both exhaust manifolds are running cool. However the Gen III cool fuel module housing is running hot on the starboard engine. Both starboard and port fuel module temps were at 74 degrees with engines cold/off. After 15 minutes with both engines running the port fuel module housing was at 76 degrees while the starboard module housing was at 107 degrees. Discuss this with Mercury tech support concluding that the fuel module water jacket which circulated sea water is likely clogged causing the fuel module to over heat and possibly vapor lock. They suggested replacing the fuel module water jacket or the entire Gen III fuel module... very expensive options. Any experience with clearing this without module replacement?
Fyi due to age no warranty help from Mercury with this problem..

[wingless]

There is lots of online information that Mercury will provide warranty replacement covering free parts when dealership labor is charged / purchased.

Has that been explored? Has that recently been discontinued?

[garkov]

I asked the Tech Support guy at Mercury Marine about the service bulletin and cost reimbursement and he said directly that there would be no coverage due the age (2006 Gen III module) which is disappointing. Asked if he could direct me to a Mercruiser certified mechanic (which means they work at a Mercury dealership) in my area which he did. Later I found out that here in the Charleston SC area Mercruiser dealers won't work on your boat if it's over 10 years old or if it wasn't purchased from them. Also very disappointing!
Through a recommendation I have found a mechanic that seems very familiar with these engines and the problems with the Gen III fuel module. He may be able to clean/clear the water jacket cooling water passages but can't get to it for a week or two. He will assess it when it's removed to determine the best course for repair. The big question will be... does it make more sense to just remove and replace the original Gen III Module & hoses with a new one (very expensive) vs remove the old one, clean the water jacket, replace the hoses/fittings and reinstall? Thoughts?