120 mercury sport jet starting problem

[bigcat1061]

i have a 120 sport jet in a bass tracker pro jet 18 1995 model.cranks good when cold --runs great--but after you run it and stop-it will not crank back after you turn it off--if you let it set about 5 minutes it will crank but its hard starting sort of like its flooded-- but when engine has been run and turned off it will not crank back right away--i have unpluged rev limiter but same problem. on the key switch does the push in feature control choke or some kind of fuel primer--when you push in on the key switch i doesnt click like the older push to choke motors i have had

 

[Waterbugtoo]

Re: 120 mercury sport jet starting problem

That is a common issue with many Sport Jets. It has an enrichner valve (similar to a choke) on it. Without modifying, about the only thing you can do is make sure engine is in good tune and adjustment, and see that fuel pump and carbs are in good shape. I have heard of installing a squeeze bulb on the fuel line to help starting when cold. That definitely saves the battery and starter.

 

[bigcat1061]

Re: 120 mercury sport jet starting problem

thanks for your reply --i dont have a problem starting it cold only hot--any idea

 

[jim dozier]

Re: 120 mercury sport jet starting problem

I have no experience with this particular motor but if it starts well when cold but not when warm, it could be running a bit rich (for a variety of reasons). Are one or more of your carburetor floats sticking open and flooding the engine? Does it idle well when warm or is there and indication that it is too rich at warm idle? I don't have the answer but these are some things to think about. It sounds like too much fuel or the problem would be worse when cold.

 

[bigcat1061]

Re: 120 mercury sport jet starting problem

i stated mine was a 95 but it is a 97--when it does this if you will give it a shot of starting fluid it will start

 

[bigcat1061]

Re: 120 mercury sport jet starting problem

it idles good but when you try to start it ,it seems flooded --if you give it a shot of starting fluid it will start right up

 

[jim dozier]

Re: 120 mercury sport jet starting problem

If it is flooded which means rich, starting fluid would only make it worse. Starting fluid works when its lean or starved of fuel for some reason. By the way, the general consensus on these posts seems to be to avoid starting fluid. Maybe you are running hot and the engine is hard to start until it cools down a bit. Have you investigated the enginge temp. Is there a good pee stream out the back? If you have the right amount of fuel and spark it will start. If and when it does start warm does it run OK?

 

[jim dozier]

Re: 120 mercury sport jet starting problem

Another thought and question. You say that it starts well when cold but not when warm. Do you choke/enrich with the key push when you cold start? Have you tried that when warm? If the idle circuit is running lean it may start anyway when cold if you choke/enrich it with the key push. If the idle circuit is running lean it may need to be choked/enriched with the key push even when warm. The fix would be to properly adjust the carburetor idle circuit mixture so that it is proper.

 

[bigcat1061]

Re: 120 mercury sport jet starting problem

once it starts its fine--doesnt matter if you use enrichiner or not-infact it doesnt seem to make a difference hot or cold when you push the key in-i dont think its running hot,no warning buzzer and will run as long as you want @wot

 

[bigcat1061]

Re: 120 mercury sport jet starting problem

on these inboard jets i dont think they have a pee stream i havent seen one on mine

 

[jetdriven]

Re: 120 mercury sport jet starting problem

I think that jimd has offered you some good advice so far. I have a SportJet 90 that has had the same problem as yours, plus many others. Mine is finally running great. Our engines are very similar. For more than two years I could not start my boat without starting fluid, or by dripping some gas down into the carburetor throats. To make a long story short, I corrected this problem by setting my floats such that the fuel level was a little lower in the float bowls. The manual tells you that the float surface should be parallel with the surface of the base of the carburetor. I set mine just a hair different from this. Just a noticeable amount. The problem went away instantly. I fought this for years; even tried to pay someone to fix the starting problems. Nothing worked. Maybe this will help you some. <br /><br />You should be able to hear your choke mechanism "click" when you press your ignition key. You had asked about this. <br /><br />If you don't have a manual, you can get one on this website, or get the official mercury service manual for your engine at www.stemtostern.com which is a big help. <br /><br />If you try the carburetor maintenance and it doesn't help, I would check engine compression and stator output next. <br /><br />Good luck.

 

[jim dozier]

Re: 120 mercury sport jet starting problem

Well I'm about out of suggestions. From your description and the fact that it runs fine once started it seems pretty much a fuel problem. Can't tell from your story whether its too much or too little fuel at idle, but its one or the other by default. You might pull the cover on the engine and try choking the carburetors with the palm of your hand and see if it starts, if so you need more fuel. If fuel is dripping out the carburetors you got too much. Give it more throttle if you think its flooded. I'll shut up now.

 

[jim dozier]

Re: 120 mercury sport jet starting problem

Well I'm about out of suggestions. From your description and the fact that it runs fine once started it seems pretty much a fuel problem. Can't tell from your story whether its too much or too little fuel at idle, but its one or the other by default. You might pull the cover on the engine and try choking the carburetors with the palm of your hand and see if it starts, if so you need more fuel. If fuel is dripping out the carburetors you got too much. Give it more throttle if you think its flooded. I'll shut up now.

 

[bigcat1061]

Re: 120 mercury sport jet starting problem

thanks for all the help

 

[bigcat1061]

Re: 120 mercury sport jet starting problem

jet driven --was your starting problem hot or cold

 

[jetdriven]

Re: 120 mercury sport jet starting problem

My starting problem was pretty much all of the time. Once started with fluid, it ran just fine. My engine was definitely flooding before I changed the float level. My plugs were wet with gas without a sign of firing until I used a little starting fluid.

 

[ODDD1]

Re: 120 mercury sport jet starting problem

Bigcat, two things spring to mind...1, if this ia a fuel problem a hard restart hot usually means the idle mix screws are set too lean...try backing them out a quarter of a turn and see if it helps....two, if you have exhaust gaskets that are leaking you could be wetting down the lower two cylinders, causing a hard start...

 

[russthemuss]

Re: 120 mercury sport jet starting problem

Check the auto enricher.On a cold engine the resistance between the 2 yellow wires should be 18-20 ohms.As the engine warms up the resisitance will increase.Maybe it is staying on after your first start and causing the engine to flood.It only works if the carburetor butterfly's are fully closed.Try starting it on wide open throttle,which would effectivly cut out the enricher.<br />You wont get any clicking sounds from it as the wires operate a heater inside it.<br />Starter fluid will stuff your engine! Try spraying a little premix instead.