1967 Mercruiser 120 IO w/ vapor lock

[Prof1967]

I am the original owner of a '67 Sea Ray with a 120 Mercury Mercruiser engine (modified Chevy II 153 cu in engine). For perhaps 30 years I have experienced hard starting after several hard runs of 15 minutes or longer. Just turning the key won't start the engine. I have to lift the lever that says "lift for cold start" and then it usually starts at fast idle. I then pull down the cold start lever and sometimes it will die. If it does not die then it will when I attempt to put into forward gear. Very frustrating. I have rebuilt the 2bbl Rochester carb many times over the years and have tuned it up as well. I finally realized after all this time that I may be experiencing vapor lock and thats what is causing my problem after the engine gets warm. What can I do to correct this? I noticed that I have a short hose that connects with a T before the fuel filter and reconnects with a T after the fuel pump. I thought this was supposed to take care of vapor lock. CAN ANYONE HELP ME FIX THIS ANNOYING 30-year-old problem?

 

[JustJason]

Re: 1967 Mercruiser 120 IO w/ vapor lock

vent the engine compartment better. The 2x4 trick usually works fine on older boats.

 

[Prof1967]

Re: 1967 Mercruiser 120 IO w/ vapor lock

Don't really need any poetry or witicisms. I need some realistic suggestions to solve my problem.

 

[Don S]

Re: 1967 Mercruiser 120 IO w/ vapor lock

vent the engine compartment better. The 2x4 trick usually works fine on older boats

The above was his answer to your question

Below is his signature line found on evey one of his replies. Yeah, it's hard to tell the difference isn't it.

just because you found it that way... doesn't mean it's supposed to be that way.

If you have an issue, and you find a problem, that's great! But do not stop at the first problem you find. The older the engine is, the chances of it having more than 1 problem goes up exponentially!!!!!!!

Boating has always been a rich mans hobby. Buying a new boat gets cheaper every year, but the maintenance, the repairs, and the overall cost of ownership of a boat has never gotten any cheaper.

 

[Prof1967]

Re: 1967 Mercruiser 120 IO w/ vapor lock

Pardon my ignorance but what exactly is the 2x4 trick. I assume it has to do with more ventilization.

 

[Don S]

Re: 1967 Mercruiser 120 IO w/ vapor lock

Pardon my ignorance but what exactly is the 2x4 trick. I assume it has to do with more ventilization.

Absolutely. It allows the hot air out of the engine compartment. But unless your engine runs over 180? and it's 90+ outside, I seriously doubt you have vapor lock problems.
But the 2X4 will allow some extra air in the engine compartment. to keep things cooler. Wouldn't hurt for a quick and easy test.
After 30 years, what's anohter weekend.

The fact is, you have a coke stove that opens and closes the choke. Does it work correctly? Too tight and it will flood, too loose and it will be hard to start cold.

Might want to download the OEM service manual for your engine. It's up in the Adults Only sticky at the top of the forum. Free too.