Mercruiser 120 starting with starter fluid only

[atfritz]

I am sorry if this has already been discussed but after spending the morning searching I still have not found a solution. I have a mercruiser 120 on a 1978 Drifter that I am having some issues with. When I pump the throttle I see gas squirt but it won't turn over or even kick like it has fuel. If i spray some starter fluid or carb cleaner into it it turns right over and runs like a champ smooth as can be. I can leave it running for as long as I want and it doesn't sputter or die. If i immediately try starting it after I turn it off it starts right back up. If i wait until the engine cools down (few hours or over night) i cannot start it again without starter fluid.

At first i thought it was the fuel since I saw it squirting but not starting but would it still be considered a fuel problem if after it starts it runs like a champ? It almost seems like the spark plugs are not igniting the fuel until the engine is warmed up. I was going to take a squirt bottle down with some fresh fuel to check to see if that makes a difference. Was also contemplating taking some new spark plugs down and see if that does anything. If anyone has any suggestions please let me know. it would be greatly appreciated.

 

[Don S]

Re: Mercruiser 120 starting with starter fluid only

I am sorry if this has already been discussed but after spending the morning searching I still have not found a solution.

It only gets asked about once every other day or so. Common problem, however the answers vary a lot, so it's a good thing to start a thread and ask.

When was the last full tuneup? Do you have bright blue spark that snaps from the coil wire to a clean ground?
Do you pump the throttle a time or two to set the choke, then leave the throttle to about 1/4 when starting cold?

 

[Fishermark]

Re: Mercruiser 120 starting with starter fluid only

Welcome aboard!

Get rid of the starting fluid - it can cause more problems than it solves. It is certainly a fuel problem of some sort. Does your choke work properly?

How are you trying to start it? Every carb likes a little something different when cold. Usually several pumps of the throttle with the throttle at about half throttle till it starts is a good initial thing to try.

 

[Don S]

Re: Mercruiser 120 starting with starter fluid only

It is certainly a fuel problem of some sort. Does your choke work properly?

I wouldn't go so far as to say that. If he only has weak spark, it might not start on gas, but it would on starting fluid.

 

[Fishermark]

Re: Mercruiser 120 starting with starter fluid only

Fair enough, but it seems if that were the case it would not "run like a champ" once it got started either.

 

[Don S]

Re: Mercruiser 120 starting with starter fluid only

What if the hot start wire wasn't connected to the starter? Reduced voltage only while cranking, plus the voltage always takes a drop when cranking anyway. That's why the hot start wire is there.

 

[atfritz]

Re: Mercruiser 120 starting with starter fluid only

Mark, back when i first got the boat I would always just pump it a few times, leave it at 1/3 to 1/2 throttle and it would turn over and run well. It just seems like over the past few years that it would either take more pumps or not start at all.

Don, I will check the spark from the coil wire to a ground this weekend when i go down to the lake. Also you mentioned a hot start wire. Is this wire quite noticeable. I never really looked for something like this and might be the problem. It not producing enough spark or heat to ignite the gas when starting seems like the problem. I am going to take down a squeeze bottle of fresh clean gas when i go down this weekend just to rule out old gas or water in the gas.

Thank you both for quick replies. I will post back after the weekend with what I find out good or bad.

 

[Fishermark]

Re: Mercruiser 120 starting with starter fluid only

The "hot start wire" Don is referring to is simply a wire from the starter to the coil that supplies a full 12 volts to the starter during the cranking phase. After the engine starts, the voltage is reduced through the resistance wire. If you have not messed around with the wiring, it should still be there.

When the engine is cold, remove the spark arrester and pump the throttle handle. See if the choke closes or not. Still sounds like a fuel problem to me, but if it has been awhile since you have done a full tune up, that would be in order as well.