"Vapor Lock" on 1965 Mercury Outboard???

[Chipso]

Hi:<br /><br />Being new to boating, is there such a thing as <br />"Vapor Lock" similar to what we used to have in some of the automobiles(50's-60's)in outboard motors? I have a 1965, Mercury 650, 4 cyl. outboard engine, Ser No. 1803488. My friend and I have been rebuilding and fine tuning over the winter. We are at the point now when we put it in the water, it was running like a charm all over the lake, until I got back to shore and trying to dock. The engine stalled and I had trouble getting it started again. Plenty of gas, but I finally had to choke it again, even though the engine was hot,in order to get it running. My friend, Forrest, said it almost had the symptoms of "Vapor Lock" in the old cars, where the gas would get so hot, it would almost start to boil and you would have to wait till it cooled down to get you engine going again. We both weren't sure if there was such a thing in outboard engines?<br /><br />Any thoughts will be appreciated

 

[ZmOz]

Re: "Vapor Lock" on 1965 Mercury Outboard???

I haven't ever heard of it in outboards, but I don't see why not. You might want to check the vent on your gas tank, and take off the gas cap next time it won't start. A lot of people forget to open the vent or it gets clogged, killing the motor eventually. I've been guilty of this myself.

 

[Chipso]

Re: "Vapor Lock" on 1965 Mercury Outboard???

Hi ZMOZ:<br /><br />Thanks for your reply. I'm sure the vent was open, as I have experienced that before, but I will try and just take the cap off just in case the vent might be clogged somehow.

 

[Chinewalker]

Re: "Vapor Lock" on 1965 Mercury Outboard???

The symptoms you describe of having to choke a warm motor tell me that you might be idling on the lean side. Try opening up the low speed needle valves 1/8 turn each...<br />- Scott

 

[kozman01]

Re: "Vapor Lock" on 1965 Mercury Outboard???

I have an old Clymer manual yet I can't seem to find the needle valve adjustments in the book. Would you mind advising me where these things are at. I have these same symptoms on my 69' Merc 800. Thanks!

 

[Chipso]

Re: "Vapor Lock" on 1965 Mercury Outboard???

Hi Chinewalker:<br /><br />Thanks for the tip, didn't know that about the low idle. We were trying to get the idle down as far as possible to help with the shifting. Maybe, we did go a bit to low. I will try that and see if it works in the next day or two, when I'm able to get the boat back in the water.<br /><br />Thanks!

 

[Chinewalker]

Re: "Vapor Lock" on 1965 Mercury Outboard???

Kozman,<br /> Most of the Tillotson produced and Mercury copied Tillotson style carbs (carb bowl on the side of the throat) have a low speed needle screw, usually at about the 2 o'clock position when looking at the carb throat. It will be a slotted screw, usually recessed a bit in the casting. I'm not as familiar with the later carbs used on the bigger Mercs, so I can't say which yours should have...<br />- Scott

 

[Chipso]

Re: "Vapor Lock" on 1965 Mercury Outboard???

Chinewalker:<br /><br />You were right!!!! I opened the low speed valves on both carburetors just a bit and it was running much better at idle out on the water today. Didn't stall when I tried to shift in forward and reverse and didn't have to choke it again to get it started, when the engine was already hot.<br /><br />Thanks again for your help!<br /><br />Chipso