5.7L EFI Mercruiser 2000 Chaparral won't start when warm

[kfm]

I am on vacation with my family and my 2000 Chaparral 5.7L EFI Mercruiser Bravo III started as usual when cold, ran for a couple of hours, and after I turned it off and let it sit for a couple of hours, wouldn't start.

This happened once prior to going on vacation, but the mechanics in Raleigh had a 2 week backlog and I couldn't get it in. After speaking with my "expert" friends, I siphoned the fuel and have fresh gas in the tank. I have never had a problem with the boat. Again, the last 2 times out, it starts perfectly and runs great, but after stopping for an hour or two, it won't start. The starter is working fine, but it never fires. It just keeps grinding.

The first time this happened, it started fine the next morning. Any clues on what could be the problem?

Thanks

 

[Pete104]

Re: 5.7L EFI Mercruiser 2000 Chaparral won't start when warm

Do you acces to a fuel pressure gauge? If so, check the preesure. You need a vauum tester as well, to measure how "pull" there is from tank!

Do you atleast hear the pump run when you turn the key on?

 

[dubs283]

Re: 5.7L EFI Mercruiser 2000 Chaparral won't start when warm

when the engine will not start have you checked for spark??

 

[BIGALF]

Re: 5.7L EFI Mercruiser 2000 Chaparral won't start when warm

Cary,NC in June must be pretty hot. If the engine cranks over but does not fire it could be a vapor lock. My 5.7EFI Bravo III ran fine until I stopped for 1 hour . Then it would not start until the engine cooled. That took about 3 hours or more, then it would start. I put a fuel buster pump and a in line water check valve on that did the fix. Boat runs fine now.

 

[Dshow]

Re: 5.7L EFI Mercruiser 2000 Chaparral won't start when warm

Yep, sounds like vapor lock. There are numerous posts on the subject. Check this link -> http://forums.iboats.com/showthread.php?t=462782

 

[kfm]

Re: 5.7L EFI Mercruiser 2000 Chaparral won't start when warm

Thanks for all of the responses. The boat started when it cooled, and by these posts and searching I believe the vapor lock diagnosis is correct.

I very recently replaced the impeller and some of the pieces made it to the thermostat housing. The engine is cooling properly now. Is it possible that a small piece of the impeller is stuck in the fuel cooler?

 

[Pete104]

Re: 5.7L EFI Mercruiser 2000 Chaparral won't start when warm

The thermostat is far ahead of the fuel cooler. Sure, there may be something there. But, worst case, the blockage is probably going into the manifolds. You have follow the cooling system hose by hose to get all the broken pieces out.
You may also have other issues that aren't obvious. What's your temp running WOT? Point being, exhaust flappers blocking exhaust.

 

[kfm]

Re: 5.7L EFI Mercruiser 2000 Chaparral won't start when warm

When I got to the thermostat housing and found the impeller pieces, I stopped. I didn't follow the hoses to the exhaust manifold, but will check all the hoses. When the engine is warm and I'm driving on the lake, the temperature gauge reads 180 degrees, and the needle stays steady until I stop and idle when the temperature drops maybe 20 degrees.

 

[BIGALF]

Re: 5.7L EFI Mercruiser 2000 Chaparral won't start when warm

The engine gets the hottest after it sits for about 15 minutes/30 minutes. This is called a heat sink. This is when you get the vapor inside the fuel line that causes the vapor lock when you try to start it up before the engine cools down.
Try opening the engine hatch when you stop after you run at idle speed for about 5 minutes. Also, if you have a a fuel cool system you should put a in line check valve in front of the fuel cooler before the engine to keep hot water from backing into the fuel cooler when you turn off the engine. This is a cheap fix. Try this before you put the fuel buster pump.

 

[pumphouse]

Re: 5.7L EFI Mercruiser 2000 Chaparral won't start when warm

vapor lock is most likely, take a small bag of ice from the cooler and put it on top of the vapor seperator for 20 mins and she will start