Mercury Motor wont start when hot out.

**KIRCHNER** · 08-15-2018, 10:45 PM

id they ck stator cold and hot? CHECK idle timing should be 0=4 atdc.

**Bass man** · 08-21-2018, 07:47 PM

I checked water temp coming out of motor after short run it was 113 degrees. Made a run to other side of lake idle for 100 yards turned boat off,fished for an hour went to make another run boat started and killed. After that all it does is turn over. Checked head temp hour after that and it was around 119 degrees. I did check timing last year when I had the problem and it was fine. Everyone seems to be stumped.

**flabum1017** · 08-21-2018, 08:09 PM

Did you check for spark and fuel when it did not start?

**BOATMANBLUES** · 08-21-2018, 08:11 PM

When you shut the motor down after a run , the temps climb inside the cowling....if it's really hot like it gets here in SC in the summer,the cylinders will dry out and not want to fire back up without some extra fuel to wet them down...on a carb motor you have a choke to bump to get it going.....if your motor runs fine other than the hot start problem and will start right up with a shot of gas, you can rig a choke on that efi...find the yel/red wire from the ECU and wire it to the choke wire on your switch...it usually runs up to the solenoid..pull it loose and run it on up to the key switch choke terminal...when this wire gets 12v it operates the fuel enrichment circuit...

**Bass man** · 08-22-2018, 05:14 AM

Flabum, Yes we have checked spark when it wouldn’t start spark is good. Fuel pressure is good at the vst pump.
Boatmanblues we have spayed in to the injectors after it wouldn’t start it would run for a couple seconds and that was it. So some reason it isn’t getting fuel to the injectors. Thanks again.

**flabum1017** · 08-22-2018, 11:09 AM

The fuel could be vaporizing in the fuel rails, vapor lock. What fuel are you using? Any alcohol in it? Alcohol gas tends to vapor lock easier.

**Bass man** · 08-22-2018, 07:30 PM

Flabum, I’m using And have always used Premium with no Ethanol. Thanks again for trying. I was told by my Mechanic who contacted A Mercury representative to try switching to champion plugs instead of the NGK wish me luck.

**superboattwin250** · 08-22-2018, 07:45 PM

Try a different ecu. Does the motor use switchboxes ? I had this happen when a switchbox was going bad and it wouldn’t tell the ecu to fire the injectors.

**Bass man** · 08-22-2018, 08:32 PM

Superboattwin250, No it don’t have switchbox, it has I believe a throttle control box that runs the coils. Which I have replaced. I’m not sure if you read my first long post? Lol I sent the ECU to Simmons to have it rebuilt. However if the plugs don’t work this weekend my friend has an Ecu I’m going to try. Thanks

**flabum1017** · 08-22-2018, 09:06 PM

an injector noid will tell you if the injectors are getting fire...... you know you got spark......

**Bass man** · 08-23-2018, 11:56 AM

Thanks again flabum, never used this before I see there not to expensive. Is this something you can do on the lake when it quits, or do you need to tear half the motor apart to do this? Thanks

**Bass man** · 08-27-2018, 09:19 AM

Had it out this weekend no change. Tried friends ECU that didn’t help. The other thing it did do this weekend, was when I went to check it after letting it sit. It started but was like it was only running on a couple cylinders. Was shaking real bad and sputtering would only get up to 2000 rpm. Usally when this happened in the past it would take off. This time it didn’t it killed and then just turn over.

**Steve Pope** · 08-28-2018, 07:42 PM

Try the air temp sender on the side of the air plenum. disconnect it and the fuel mix will be 10% richer. See if this helps the hot start. The air temp sender could be signaling the ecu that the air is way hotter than it really is so the ecu will deliver less fuel.

**Raffuss** · 08-28-2018, 08:24 PM

Gas tank vent plugged???

**Bass man** · 09-03-2018, 08:30 AM

Thanks Steve, for advise. Had the boat out yesterday it acted up once where it didn’t want to take off acting like it was only firing on 2 inectors again, then it took off. We fished for another hour then went to leave, it started and killed.So I unplugged the air temp sensor that didn’t work. So I pulled the wite off the bottom of fuel filter and it started. Could this be the problem? Something wrong with the probe telling the Ecu not to start? Or was it just coincidence? Thanks again