1986 Merc 470 3.7l Idles fine then dies

[wakepro82]

Just purchased a 1986 Sea Ray Seville II with the Mercruiser 170hp 3.7l with an Alpha One outdrive. I have already searched and come up with a lot of info, so please don't tell me to search. My problem is that I can get it to idle fine on the muffs, but when I give it some throttle it revs up and then dies. It will fire right back up with out a problem. I am going to do a carb rebuild and replace the fuel filter. What else should I check/replace?

 

[stingray43]

Re: 1986 Merc 470 3.7l Idles fine then dies

Check the + side of the coil. It sounds like your resistance wire from the choke is not on? If your getting 12 volts it is too high and it should be between 7 and 9 volts.

 

[Pete104]

Re: 1986 Merc 470 3.7l Idles fine then dies

You would also be frying points. Good carb cleaning should do it.

 

[Eric 3.7LX Alpha 1]

Re: 1986 Merc 470 3.7l Idles fine then dies

Don't know how much background you know of that engine. The 470 is very sensitive to overheating, can damage a head gasket easily if it happens. Make sure you have a good working temp gauge, and if the age of the impeller in the drive is unknown, replace it as the new owner. They should be done about every 3-years anyways.

Here are some carb rebuilding videos from a previous thread on here if you've never done it before.
http://forums.iboats.com/showthread.php?t=362542

 

[wakepro82]

Re: 1986 Merc 470 3.7l Idles fine then dies

I will check the power on the resistance wire today. Also, to clarify, motor idles fine when i give it throttle, it revs up. it will stay revved up but when i give it any more throttle thats when it dies. I might try to post a video later if I can find our camera. Thanks for the advice so far!

 

[wakepro82]

Re: 1986 Merc 470 3.7l Idles fine then dies

So I just went out and looked over the wiring. I have a black wire coming from the coil (+) that goes near the choke but not connected to anything. I have two wires coming off of the choke element but neither looks like they are connected to the coil in any way. I looked through the Merc manual and it looks as though i need to splice into the purple wire going into the choke so it connects to the coil. Is this correct?

 

[wakepro82]

Re: 1986 Merc 470 3.7l Idles fine then dies

So I have narrowed it down to a fuel problem I think. The resistor wire is connected correctly and I checked the resistance as per the manual. I have a fast idle, and cannot get it to slow down. I disconnected the throttle linkage to see if the cable was out adjustment and that is not the case. I turned the idle screw all the way in and it still does it. Think the carb is leaking? I also am pretty sure there is bad gas. So I am ordering the rebuild kit for the carb and emptying the tank. What else would cause a high idle and then a stall when revved?

 

[Marada20]

Re: 1986 Merc 470 3.7l Idles fine then dies

check fuel pump/fuel bowl and inline filter at the carb.