One engine starts fine, the other takes forever

[jebwm]

So the last couple of time that I've taken the boat out, the starboard engine cranks right over, but the port engine takes some fussing with to get it to stay running. Allow me to elaborate a bit...

I can hold the key forever and it will try and crank all day long. Eventually it will start to run but then stall out. After I do this a few times it will run longer and longer each time before it tries to stall out again. Once I get it to a point where it will run for 15-20 seconds, I just gun it and it seemingly clears itself out. Today the RMPS were limited to around 6k for like 5 seconds then shot right up to 10k where it was supposed to be. To make this even more tricky (or perhaps simpler), once I do all of this it is fine for the rest of the day. It's only when I first put the boat in the water that I have this issue. Once I get it going, it will crank over completely normal all day long. It almost seems like a fuel filter or screen is clogged and it just takes a bit to clear it out or something. Any suggestions? Thanks

 

[Bruce]

It does sound like a fuel issue.

When was the last time you changed the spark plugs?

 

[jebwm]

It does sound like a fuel issue.

When was the last time you changed the spark plugs?

At the beginning of the summer and they probably have less than 7-10 hours on them total.

 

[Bruce]

I would start by adding a can of Seafoam to the fuel tank.

Each engine has it's own fuel pump. The filter is built into the pump. It is possible that one pump is clogged or failing. I am bit sure if the fuel system has a check valve but a check valve failure may be allowing fuel pressure in the line to drop between uses.

 

[jebwm]

I'll pick up some seafoam. Good idea. A check valve sounds probable, but like you, I have no idea if there is one or where it is, but that would make sense that fuel pressure is lost and I basically have to re-prime that engine to get it to function again.

 

[Bruce]

The check valve is part 14 in this parts diagram http://www.partspitstop.com/oemparts/a/yam/50039eb5f870021f60a11528/fuel-tank

 

[jebwm]

The check valve is part 14 in this parts diagram http://www.partspitstop.com/oemparts/a/yam/50039eb5f870021f60a11528/fuel-tank

Dang dude, thanks! I'll try the seafoam first and see if that helps out. If not I will investigate the check valve. For $44 bucks it won't hurt too much if I replace it and it's not the proper fix.

 

[itsdgm]

That check valve is on the fuel tank vent hose though. I doubt that would be the issue. However, it's pretty easy to pull the fuel pumps and take a look at the screens on the bottom. If it was mine, I'd pull both pumps, clean the screens and swap the pumps from one engine to the other. That way if the problem persists on the same engine it would rule out the pump.

 

[betterwhenitswetter]

I seriously doubt seafoam will help, you need to start checking fuel pressures. Do you have Yamaha YDS diag... software?

I don't really like the idea of swapping parts from side to side (its a last resort), you can cause more issues or open a can of worms.

on my waverunner the ECU was bad it was giving me all kinds of crazy issues, from weird readings to massive amounts of fuel in my cylinder.

 

[bronze_10]

In old cars it sounds like there is air in the fuel lines.. maybe from a small Crack or splir so we here just large enough to allow some air in... over time the fuel in the line will slowly drain away from the engine. When the full pump starts it has to push the air that has accumulated in the line out first before the engine receives steady fuel.... it would seem that this would also be plausible in boats too but I haven't heard anyone have the issue...

 

[Gym]

I would still pull the spark plugs to check their condition. You may have a fouled plug or the gap may not be set correctly. While checking the plugs also check the condition of the air filter. Make sure it's not oil soaked.

 

[Mainah]

Could not hurt to check compression. Good Luck.

 

[jebwm]

Thanks for the input everyone. I don't have the YDS software but this may be the excuse to pick one up.

GYM - I will check the spark plugs and gaps. They are cheap enough so I'll probably just replace them

Mainah- I checked the compression at the beginning of the summer before I bought the boat and all was good. I guess that doesn't mean it could be off now, but something tells me it will be fine anyways.