New Mercury 600 starting problems when hot
 

I have a brand new 600 in my new boat and it does not want to re-start after it sits for about an hour after a run. Cold start is fine. Mercury is saying it's from the heat and the fuel is boiling in the rails. Outside temp was 105. I tried opening the hatch to cool with no luck. I tried turning the key on and off to cycle fuel with no luck. It still takes about 8 tries to get it to start. Anyone else have this problem?

I had the exact same problem with one of the 525's in my boat. It turned out to be that I had R&R'd that engine and when it was put back in the boat, the main fuel line was too close to the bottom of the engine. I lowered it and it solved the problem. Having said that, your outside temperatures are much higher than mine so it sounds like you could be experiencing a heat soak flood condition and the fuel maybe boiling off. Make sure your fuel cooler is not clogged also.

Heat soak is what they are saying but there are many other guys running the 600 in hotter temps with no issues. You would think a brand new motor would not have this issue. Ugh!!!

It's not always the motor, but the engine compartment that it sits in.

What could be wrong with the engine compartment? Not enough air? I open the hatch after each run and let it cool and still no luck.

Are you running E10 fuel ????

Yes. That's all they have in my area. I did hear that the ethanol separates from the fuel in temps above 100. I wonder if they make something that will stabilize the fuel if that's the problem. My last boat and all the other boats that use the same fuel are not having this issue. I wonder why the 600 is so different. Thanks for the help.

sounds like vapor lock to me

could be check valve in the electric fuel pump

other possibilities could be coolant temp sensor or IAC as well so have engine scanned and fuel pressure checks and fuel vacuum tests

Fuel vacuum test thats are higher than spec can cause huge vapor lock issues among other problems.

E 10 separates when water in the fuel is present. take some fuel samples in a clear jar to look at. water mixed with E10 sinks to the bottom and fuel sits on top.

your engine is new I would have a Merc certified shop and the Merc rep look at it and warranty the issue(s) instead of everyone throwing darts up here about it including me. We all are blind trying to fix a new motor here that's what the warranty is all about as well. Complain about the huge inconvenience you are having. Call Merc is the best advice I can give you.

With the warranty you can take it to any Merc dealer in the world as many times that is needed to get it fixed to your liking.



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forgot could be anti siphon valve on top of the gas tank that the fuel line is connected to that is sticking from heat soak. Sometimes those anti valve valves can be just as much a problem when brand new compared to 20 years old.


Been there with new boats as well that experience problems the anti siphon valve.

Overtightening them can distort them too. Most are aluminum.

The boat builder has been talking to Merc and trying to get some answers. There was another boat with the same motor built just before mine and he is having the same problems. He also boats at the same lake. So far they just keep blaming the hot air temps causing the fuel to boil. I will look into everyone's suggestions while I wait to hear back. So cool that you all take time to respond.

Do you run the motor for a few at idle speed or just shut it down hot after wot runs? A few minutes at idle with the hatch cracked might help (maybe you are already doing this but just a thought)

do this:

1. push the throttles to the wood.
2. turn the ingition key, if you have one, on.
3. try to start the motor until it girgles and then stop.
4. pull the throttles all the way back.
5. repeat step 2 & 3.

*might take two or three times of repeating this until it fires. but, it usually works after the first attempt. if it does not start, do not attempt to keep starting it. immediately go back to step 1 and repeat process.

this works on 600 & 700's.

walla!!!!

Yup. I always let it idle and cool down.

I will give it a try. Does that just cycle the fuel? You would think they could fix this issue by now without having to do all that. I will update what did the trick

agree. i am surprised as well. a notable person told me about this trick and it never failed me, and i have actually helped several folks who i saw struggling at the dock to fire up, and another guy who was unscrewing certain parts on the motor to release the lock. this is MUCH easier and was fail proof on my 600 efi's.

i guy in an OL, with a fairly large ego was blocking me in at Gilbert's at the Key Largo stop on the Miami Boat Show PR and so I politely walked over and offered to help him start it up. he smugly told me to go ahead.... and so i did. it started in only a matter of a couple trys. BUT.... on the OL's (back then, at least), they only had one ignition switch. so, after the first motor fired up, i let it run for a minute or two before turning it off and repeating the process with motor 2, and then restarted motor 1.

hope this helps.

PS: it's been a while....

i forgot, turn the ignition key on and off 5 or so times, priming the motor, rather then just turning the ignition switch on and then trying to fire it with the throttles pushed to max throttle.

sorry --- old age.... 40's are not for amateurs!!! lol

I have nothing close to 600cs's but my 454 mag mpis did that even after I ran the fuel returns to tank. In speaking to Eddie Young, he said my next step should be to remove the fuel filter head off the block and get the fuel line that runs underneath the motor away from it.

While I am not familiar with the 600 fuel, your getting vapor lock (worse with ethanol or winter mix fuel) which is all heat related. I didnt have any issues with summer fuel (nonethanol) but winter mix I put in was giving me mild vapor lock.

Insurance: keep a bottle of sea foam in the boat and if happens, Pull filter off an fill back up.

On computer controlled marine engines you have 7 modes of engine operations and the clear flood mode is one of them but this is not active for ECM and PCM 555. It is active for MEFI systems. This is for if the engine gets flooded of fuel, it can be cleared by doing so - Advance the throttle to 1/2 min to 3/4 open. when the throttle position sensor reads between 50 % to 75 % at cranking rpm the ECM will not fire the fuel injectors at all. This allows air into the engine but no fuel so the can start basically as a non flooded engine. Once the engine starts and exceeds over 300 rpms the ECM cancels the clear mode and then enters running mode. Again not active on ECM 555 and PCM 555.

If you have to advance the throttle everytime to get your MPI marine engine started - you have a problem somewhere in the system. It can even be a sensor reading input to the ECM especially for the IAC and or coolant temp sensor and or the TPS sensor and of course fuel related problems can be adding to the list.

Wow!! Very technical stuff. I will give it a try. Thanks for the detailed reply. I can't wait to try all these things out to see what works. It's embarrassing when you have a bunch of people checking out your new boat and it does not start. Total buzz kill.

Interesting, sure sounds like vapor lock, that I have experienced on my old 35 Nordic Flame that had 502 MPI's. I have 600SCi's in the 388, and they have about 120 hours on them, and I boat in air temps,85-95, and I have never had a problem starting, or anything for that matter, my 600 SCI's have been very reliable, (knock on wood). BUT, I will say that I always idle for a fair amount of time, (Manatee Zones, GRRRR) and always open my hatch and let them cool whenever possible. Maybe try taking a towel and soaking it in the ice cold beer cooler water and then sit the cold towels on the fuel rails to cool the rails and the fuel and give it a try... Seen drag racers do this in the Florida heat....

I think my post # 20 was taken wrong or my info was not clear enough.

1. the OP does not have a MEFI - ECM - it will be a PCM 555 Merc specific flash

2. post # 8 as I believe 99.9% its vapor lock as well but what is causing the vapor lock sometimes and a lot of times there can be something causing VL and is not E 10 related specific ? We have noting but E 10 here in the area and our weather during the whole summer is hot as hell plus are lake water temps is the hottest around. Most properly working and properly set up fuel systems for the marine engine do not experience vapor lock using the correct gas blend as well. I said most not all.

3. Clear flood mode if somehow the MEFI based engine gets flooded there is a clear flood mode to try to see if that will aid in starting the engine. Again your engine is most likely not flooding (gas) and is not MEFI based anyways.

There are things you can do to help against vapor lock.