I have a 2006 WE225 with 5.0 Merc,...

[jvsrunner]

I have a 2006 WE225 with 5.0 Merc, 230 hours. When I start it cold, no problems. After a cruise and anchoring, the engine will not start when we want to leave. It coughs, sputters and pops, not quite like a backfire. It wont catch when in neutral. It wont respond when I pump the throttle even though it is EFI (fuel injected). We let it sit for 20 to 30 minutes and I can work it to start. Yes, it is probable that I flooded it when pumping the throttle. I just had the starter solenoid replaced at a Marine Max. Alternator, batteries are fine charging at 14.0. Not overheating, at least according to temp gauge. Mr Wingless, you know everything. Any thoughts?

[wingless]

Thanks for your astute observation. The wife will concur that I think I know everything...

It sounds like vapor lock to me. The fuel system cannot pump fuel vapor and can only pump liquid fuel. Even though the fuel is pressurized, raising the fuel boiling point, once the fuel gets hot enough it changes state from a liquid to a vapor, cannot be pumped and the engine cannot operate properly.

There is LOTS of thermal mass to the engine(s), two in my case, one in yours. While operating, cooling water is removing that heat into to the raw water, w/ about a dozen means using that water flow to remove heat from the various engine systems, while the engine is running.

Once the engine stops, that cooling flow also stops. All that thermal mass is sitting inside a well-insulated "sealed" box, the engine compartment. The box is insulated and sealed to contain audible noise, but it also contains heat.

My boat had ZERO vapor lock problems in New England.

My boat always had vapor lock problems in southern Florida.

The boat would always vapor lock when stopping for an hour with the engine compartment closed, with the symptoms you've described.

In my case, the only way to prevent vapor lock was to open the engine compartment when stopped, but that doesn't work well w/ guests lounging in that area.

There are two initial steps. First, ensure the exhaust has not deteriorated. It should be possible to continuously hand hold the entire exhaust while the engine is operating after it reaches normal temperature, except for the port immediately adjacent to the head where the exhaust gas exits.

Second, run through the checklist in the Mercruiser 99-7 Service Bulletin. In my case that was followed to no effect.

In my case, operation of the existing blower system had zero effect on the problem. The intake for the existing blower system is down low, as-required to properly suck out possible heavier-than-air fuel vapor collecting in the engine compartment.

It may be that those blowers would have sufficient heat removal on your boat while parked to keep the temperature low enough to prevent vapor lock. This is my suggestion as an attempted solution to the problem. Run the existing blowers prior to shutting down and after getting underway to see if they provide sufficient heat removal.

Another potential solution is to keep the engine compartment open when stopped, so the hot air may naturally exhaust via air convection. The open engine compartment lid doesn't work well with people lounging on the boat.

https://images0.boattrader.com/resize/1/21/8/6812108_0_091020181714_21.jpg?t=1301731

https://images0.boattrader.com/resize/1/21/8/6812108_0_200820181317_45.jpg?t=1301731

The solution I implemented years ago was instead to design, fabricate and install a custom thermostatically-controlled high-air-flow heat exhaust system that maintains the engine room temperature to the setpoint by automatically toggling these new blowers on and off.

This new heat exhaust has provided 100% problem resolution on my boat over the years since I installed this system.

[jvsrunner]

Dear Wingless,
Your wife and I are in the same club. I have also suspected vapor lock and it makes complete sense. Open the hatch. Use the blowers for a few minutes after I shut down. Plus it is an easy and no cost fix. Generally, we motor to Fort George Inlet in Jacksonville and I can open the hatch after we get the chairs, cooler and tent out. So we do have the ability to try your solution. I like your thermostat idea but it may take time to implement. Thanks

[wingless]

Great.

It may be that continuous blower operation while stopped for an hour layover is required, assuming that it has sufficient heat removal to prevent vapor lock on a closed compartment.

My custom automatic thermostatically-controlled system toggles on and off for hours after operation to maintain the closed engine room setpoint temperature.

It would be very surprising to me if minutes of blower operation on a closed compartment would have any effect on the problem.

Conversely, when I open the engine compartment, automatic blower operation immediately stops because natural air convection removes lots of heat.

Good luck. Please report the results and observations.

[jvsrunner]

Good points. I will let you know, possibly this weekend. Thanks again.

[The_AVA_MARIE]

Mercury makes a low pressure “lift pump” that is prewired to plug into your existing fuel pump. The pump is installed between the fuel pump and water separator filter. It adds that extra boost need to push vapor lock through. After several seasons of aggravation with my 240 DA it was a God send after being installed. I believe Mercury originally produced them for the 7.4 engines. Mine works great, starts every time hot or cold. Good luck.

[The_AVA_MARIE]

Sorry for the typo, the pump is installed between FUEL TANK and water separator filter. Good luck.

[wingless]

Got a part number on that Mercury lift pump?

[wingless]

Here is a document and a part link that might be applicable

http://www.engineprofessional.com/TB/TB041916-1.pdf

https://www.amazon.com/dp/B005IGSW0G/?coliid=I1DU9J8DHMUYTW&colid=3W47D7IO4W4YY&psc=1&ref_=lv_ov_lig_dp_it

[The_AVA_MARIE]

I will get it Monday, pump was installed by Everest Marina in Cape Coral Fl. I’ll give them a call and post tomorrow.

[The_AVA_MARIE]

Wingless, that is it. That is the same document the Marina showed me before installing on my boat. It’s about a $500. Item installed. Well worth every penny in my case, 5.0 starts every time now. I originally installed the water intake back flow check valve between thermostat and fuel line cooler and it made very little difference. The lift pump works.

[jimaddison65]

Don't use gas with ethanol. It is corrosive and can damage the fuel system. E0 only.

[jvsrunner]

You guys are all great. Confession: I use regukar car gas but treat it with StaBil Marine. I think I will make the switch but I fear the damage is done and there is no reversing corrosion. As for this weekend, I got"lucky"? We took her out on Sat and cruised an hour to the Fort George Inlet; threw out the bow and stern anchors and then I noticed an oil slick. The good news is the engine started right up and we cruised back to the marina. The bad news is twofold. (1) Engine would not restart on the cleaning rack so no engine flush on Sat. It was all of 5 minutes from water to rack. (2) Just had the trim cylinder seals replaced at local Marine Max but now feeder lines are leaking trim fluid.
QUESTION: Would technician have removed braided feeder lines from below gimbel to rams? and not reconnected properly?