Merc 470 a little hard to start when warm...

[ntheyer]

I have a 1987 Merc 470 that starts and runs great when hot or cold. The only issue I have, and it's really not too much of an issue is warm starting.<br /><br />I have to apply about half to 3/4 throttle and hols it there while cranking for about five seconds before it starts when warm. Once it's running, no problem at all. It will idle down perfectly right away and no issue at all... What is my problem? I would think too rich, but the choke plate is wide open and functioning correctly. I also have Pertronix electronic ignition and timing spot on with new wires and plugs.<br /><br />Thanks.

 

[WillyBWright]

Re: Merc 470 a little hard to start when warm...

It's called heat soak. They hold a lot of heat and boil the gas. That leads to vaporlocking. Open the doghouse whenever you can. That helps the most. Keep the blower running, you might want two. Early versions had a 3" diameter heat exchanger which wasn't big enough. Later ones were 4" and cool much better. I even saw one recently with a fuel cooler. I imagine that was from the final years of that motor.<br /><br />One of the biggest complaints about that motor involved waterskiing. It would start right up after short periods of time. But if you were changing skiers, that was enough time for the heat soak to vaporlock the motor. They also start right up after sittimg a long time.

 

[ntheyer]

Re: Merc 470 a little hard to start when warm...

Thanks. I have the 3" exchanger. I keep my blower on all of the time since it tends to want to run hot. If I let it idle too much it will warm up too much. If I get the RPMs up above 1200, it will hold 160. I put a new impeller on it so I know it's not the impeller. I thought it was just heat soaking.