Odd starting problem after sitting for a while.
 

I have a 1997 5.7L 2 barrell Mer-Carbed Mercruiser with Alfa outdrive. The boat starts off of the trailer immediately, runs out great and is generally problem free. The engine looks and runs like new.

The only complaint I have is when we have been driving around for a while and then decide to park for 20 min to a couple of hours. When I go to restart the boat I have to bury the throttle all of the way and crank for about a minute, for it to start back up. After that it runs perfect. If I kill the motor a couple of minutes it always starts back up right away. It is only when I let it sit for a while that it does this. It is very consistant.

I called a carb shop about getting the carb rebuilt. The guy said the MerCarb isn't rebuildable and that is a normal situation because of the aluminum carb cooling at a different rate than the engine. I have had three boats now, with this being my only one without fuel injection, so I don't know if this a regular problem or not. Should I replace the carb with something else? If so what carb would be a direct replacement and would that fix my starting issue.

Re: Odd starting problem after sitting for a while.
 

Hyperryd,

I would check out your carborator's electric choke. If not there, you may have a defective coil.

Also, I would think that a 1997 carborator should be rebuildable.

I have the exact engine and carb as you and I do not experience your issue.

Shabah 198 SE

Re: Odd starting problem after sitting for a while.
 

That answers one question: Is this normal.

I'm glad for that, as it seems like a goofy problem to be normal.

Re: Odd starting problem after sitting for a while.
 

Hyperryd,

Another consideration could be a vapour lock condition. Have you made any changes to air flow, operating temperature, etc.?

Note: The Mercruiser parts manual lists parts for those carberators, so they must be rebuildable.

Shabah 198SE

Re: Odd starting problem after sitting for a while.
 

The motor is bone stock. I checked it out and there are rebuild kits available. I think I will replace the choke first and then the carb kit if that doesn't work. The boat runs great so I am thinking the electric choke might be it. I don't know how to diagnose a vapor lock, but it sound similar to the problem I am having as well. Any ideas on that would be helpful.

Re: Odd starting problem after sitting for a while.
 

Hyperryd,

One common thing to do to prevent a vapour lock is to insulate your fuel line. In your case, being a new issue, I doubt that is a solution. Are you buying fuel from a new source? Have you changed grades of fuel? Is your flame arrestor clean? Have you changed what you store in your side compartments (changing air flow)?

Shabah 198SE

Re: Odd starting problem after sitting for a while.
 

I have had this problem since I bought the boat two years ago. There is never anything exciting int he storage compartments, just towels or a towable. Most of the time they are empty.or not much there. I haven't done anything different with fuel either. I was originally thinking that the fuel was back flowing into the tank and the mech fuel pump was having to prime again at start up, but a friend who know these style pumps said that isn't likely. Hopefully I will find some time this weekend to take a look at the carb myself and see if the choke is working correctly and go from there. It really is puzzling.

Re: Odd starting problem after sitting for a while.
 

I would start with lifting the engine compartment lid(s) to cool for 5 minutes or so prior to restarting the engine. If it starts correctly then you have a vapor lock issue. Another concern would be the needle and seat in the carb could be defective and cause a flooding situation. Yes the carb can be rebuilt and kits are available everywhere, however use a marine kit which will provide the correct marine coast guard required gasket material. Do not use a automotive kit. Your fuel tank has a anti siphon valve on the outlet side of the tank. The valve prevents the fuel from flowing back in the tank from the carb. It is easy to check by removing and blowing one direction thru the valve and then the other direction. Air should flow towards the engine and not back to the tank. If so you have a bad valve. Let me know what you come up with.

Re: Odd starting problem after sitting for a while.
 

I had a similar problem with my 5.0 2 barrell I changed it out for a quadrajet 4 barrel no more problem I used that same carb on my built up 5.7 though my buddy is a wizard with carbs he built it for me upon checking the old one he said it appeared to be a float issue which was causing the bowls to empty when sitting for short periods while hot which could easily be related to your issue when cool enough your choke is working perfectly when still warm the bowls may be drying out, and there for the choke not working right away. Anyway end of the story he merely cleaned the choke assembly and carb up and it has been running on his wifes car for 5 years no problem. You might want to just pop it off and clean it up real good lube it and see if it works fine then go deeper just a thought.

Re: Odd starting problem after sitting for a while.
 

Did you ever get a solution? We are having similar issues. Thanks