We recently bought a 2002 Sea Ray...

[denisehalstead]

We recently bought a 2002 Sea Ray 185 bowrider - boat was in great shape - 180 hours on it.  When cold it starts great, smooth idle, and runs really well.  Once out on the water or after an outing we will try to start it again and it turns over but the idle is rough and then it dies.  No other indications of problems.  We try and try to restart and generally after about a half hour we get lucky and it starts - and the idle is instantly smooth again.  This is really sporadic.  We have it into the shop now......and I'm sure it will start perfectly!  Any ideas?

[wingless]

Welcome to the forum.

It sounds like heat soak vapor lock on that 4.3 Mercruiser MPI engine.

"Easy" to verify by keeping the engine compartment open during the stop, permitting the heat to escape, to determine if it will restart normally after the stop.

There have been issue w/ early Cool Fuel modules, with internal delamination, obstructing normal flow. It has been reported that Mercruiser will perform goodwill repairs, with them paying for parts and the owner paying for labor.

It might be possible to attain acceptable operation by using the existing engine blowers, perhaps during operation, but especially during short stops. It is required that those draw from the bottom (gasoline vapors are heavier than air), but heat rises, so it would be better to draw from the top.

On my custom thermostatically controlled heat exhaust system, I have two high volume exhausts, sucking to the exterior from directly above the engines. This has been 100% effective at eliminating the heat soak vapor lock on my 2000 380DA.

https://live.staticflickr.com/65535/50234638307_9c39d57e9f_c.jpg

https://live.staticflickr.com/65535/50234601893_ca104dee1d_c.jpg

[MoparBob]

What is the cool fuel module and where is it located?

[wingless]

Not knowing the engine serial number, it looks like that 4.3 does not have a Cool Fuel module, just a regular cooled fuel pump.

Here is a link that might not be correct for that engine.

https://www.mercruiserparts.com/bam/subassembly/31507/13808/60

[haskins]

Could it be a sticky carb? I had to have mine rebuilt and it exhibited the exact same characteristics.

[lady_Patricia]

I had the same problem with a Mercruiser, after much analysis it turned out to be fuel vapour lock. The fix was to replace the fuel line back-flow valve with one that stayed open when the ignition was on and closed when off. The old valve was heating the fuel due to friction.

[wingless]

haslins, welcome to the forum.

My guess is that your 2003 176 Bow Rider has the 3.0L w/ carburetor, not the 4.3L MPI fuel injected engine for the OP, w/o a carburetor.

lady Patricia, what engines are in the 2018 460 Sundancer? Aren't those Cummings diesel?

[LadyMedjool]

It’s probably the Mass Air Flo Sensor.
I have Searay SD280 and my Port engine ran fine but would not hold a idle. Would stall out in idle position. The Mass Air Flo Sensor is a “Plug and Play” item. It sits on top of the engine near the Engine air intake. Not expensive to replace.
Good luck.
Capt Mike in NJ

[Bow_Tie]

Vapor lock, had the same problem on a Mercruiser 380 MPI. Installed a inline boost pump, from Mercruiser. It was installed before the original fuel pump. Worked perfectly, Mercruiser knows about this problem and developed the low psi in line pump because of the problem. If yours is not a MPI engine, there are other fixes, like Lady Patricia stated.

[lady_Patricia]

wingless, yes the 460 Sundancer has twin 550HP Cummings. The Merc. was in a Stingray I owned about 10 years ago.

[Bill2]

Not all 4.3s are fuel injected. My 2010 185 Sport has a carburated 4.3 TKS. We find that although it does start hot, raising the sun pad for a few minutes or floating for a half hour or so does result in a quicker start due to the cooler engine.

[jvsrunner]

Hi Denise. The size of your boat may indicate that you trailer. I had similar problem with 5.0 225 Weekender. I switched to ethanol free gas and have not had the problem since. Yes everyday 87 octane from the local gas station is cheaper but it will cost you more for a tow home. Vapor lock will "cure itself" after given enough time to run good fuel through fuel rails.

[denisehalstead]

Thanks all for the assist. Ours is a 4.3 Mercruiser MPI. The comment about the cool fuel module is something we need to check out. My son as a 2000 Sea Ray sundeck with a 5.0 EFI and had a similar problem - he put in the secondary fuel pump and that worked. As far as terminology, Bow Tie is talking about an "in line fuel pump. Is that the same thing as as a cooled fuel pump??

[Bow_Tie]

Hi, the fuel pump I was referring to is installed before the cool fuel assembly (primary fuel pump) and the fuel tank. It's a low pressure pump that is plug and play with the primary pump. When the primary fuel pump is energized, the secondary fuel pump is energized as well. It a a Mercruiser part (kit) .

[wingless]

The Bow Tie supplemental fuel pump is the official Mercruiser solution for heat soak vapor lock. The vapor lock still happens, but the low pressure pump pushes liquid fuel through the system, purging the vapor back into the fuel tank, so the system works normally.

Everything I have seen about that Mercruiser kit shows it to be 100% effective.

There are two things I don't like about that solution. One is the cost. Each kit is pricey for the parts, ~$500 each engine. The other thing is that the engine compartment still gets hot as heck, especially after dropping the hook for a lunch break / swim.

My custom thermostatically controlled heat exhaust system doesn't have those two issues. The cost is reasonable and the engine compartment temperature is maintained within a 5°C range.

[Bow_Tie]

The Mercruiser pump I'm referring to was around $500 list price, but discount online stores are selling them for around $350. There are other low pressure pumps that would work, but they are not suitable for the marine environment and the safety factor and quality aren't there. Wingless stated he has a thermostat controlled engine compartment, good for diesels. But Gas engines run hotter, the heat soak being greater causes the gas to vaporize and loose fuel pressure in the line. RVP (rapid vapor pressure) is increased because of the additives in the gasoline, especially during the colder months. E10 is also part of the problem, a permanent fix is the inline secondary pump.

[wingless]

"Wingless stated he has a thermostat controlled engine compartment, good for diesels."

My custom thermostatically controlled heat exhaust is 100% compatible for a gasoline engine compartment.

The engine compartment has a 10K Ohm NTC thermistor and a pair of Shurflo Yellow-Tail blowers, both compatible for an ignition protected environment.

Yes, there is lots of thermal mass and lots of heat, but my system has zero issues maintaining the digitally selected controller setpoint temperature, cycling on and off automatically.

My solution has also been 100% effective.