Hard starting mercury outboard hot or cold

[cheapster]

I have a 94 40 horse oil injected mercury motor. I did a compression check and 3 of the cylinders were at 100 the fourth was 90 is that ok or does something need to be done. My other problem is the motor is hard to start,is the butterfly on the carb supposed to be shut even when im not pushing the electric choke. It only opens when I give it throttle. If I shut the motor off when its warm the only way I can start it is to dump fuel in the carbs. I'm wondering if my choke is stuck. You should also know it will idle good for about 2 minutes and then dies, but while driving around the lake it runs smooth at any speed. Please help I'm out of ideas I've replaced plugs,cleaned both carbs,new fuel filter,even tried fuel treatment.

 

[jbjennings]

Re: Hard starting mercury outboard hot or cold

Your compresion is suspect... Probably the cause of your hard starting, along with dirty carbs which could be the cause of your low cylinder. I'm no expert on oil injected outboards or any other. But your compression numbers need to be looked into.

 

[SaltlifeDan]

Re: Hard starting mercury outboard hot or cold

I agree with JB your compression sounds low. The butterfly should be shut when your not giving it gas. You may want to check the level of fuel in your carbs float bowls. If you pour fuel in and it runs until that gas is gone it sounds like it is starving for fuel. I have seen floats spring leaks and become heavy with fuel, this in turn causes the fuel level in the bowls to be low.

 

[jbjennings]

Re: Hard starting mercury outboard hot or cold

The 90 on one cylinder compared to the other 3 at 100 is what bothers me. However, what you're describing to me sounds like lean carbs caused by dirty passages or an air leak. Clean your carbs, check for air leaks, and see how she runs. You may catch the problem in time for it to run quite a while longer with no major repairs.
JMO,
JBJ

 

[Silvertip]

Re: Hard starting mercury outboard hot or cold

Those compression numbers are low but are not the cause the of the starting issue. No -- The plates you are looking at are the throttle plates, not choke butterflies since your engine doesn't have any. The engine uses an enrichener activated when you push in the key while cranking the engine. You didn't explain your starting procedure but I suspect the incorrect procedure is being used, enrichener is not working, and/or carbs need rebuilding.

 

[CharlieB]

Re: Hard starting mercury outboard hot or cold

Quality of the gauge can make a noticeable difference in compression, as can cranking speed, and having the throttle open or closed.

The range of pressure is more telling, having all cyl's close to within a few % of one another.

Inspect the spark plugs and piston domes for excessive carbon deposits as carbon accumulation in the ring lands can reduce compression. A 'De-carboning' procedure can improve #'s if carbon is the culprit.

How long has it been since the carbs have been cleaned? Idle passages because of their small size will affect starting and acceleration long before you notice a problem with WOT.

 

[insomnia84]

Re: Hard starting mercury outboard hot or cold

Hello

Please give me advice, I bought 1992 Mercury 60 SeaPro.

He was working last summer and this is what i dont like/is my concern:

1) he smoke more than other 40-50-60 hp mercury from same years. Most ppl say its normally, but i dont think so. it is white smoke, mostly when i turn it on, but it also smoke more than others in idle or in gear.

2) bigger problem is that i have trouble with turning him on when he is cold (specially first time in day). He does turn on, but i have to start it for more than few seconds + i push key (chock?)- nothing is better, then i give him, how is it said (sorry for my English), more neutral speed (gas?), then after some time he does turn on. He works for 5-10 seconds and dies.
Then I have to pump him again gas, and he turn on almost normally.


3) How is proper starting of him?

I admit i used low quality oil, valvoline, and I will change it + will change sparks.
But when motor is warm, he start and works perfectly (except this smoke).

Thanks!

Those compression numbers are low but are not the cause the of the starting issue. No -- The plates you are looking at are the throttle plates, not choke butterflies since your engine doesn't have any. The engine uses an enrichener activated when you push in the key while cranking the engine. You didn't explain your starting procedure but I suspect the incorrect procedure is being used, enrichener is not working, and/or carbs need rebuilding.

 

[JWH0420]

Re: Hard starting mercury outboard hot or cold

assuming ur compression readings are correct they are too low for a 2 stroke motor the 10 psi variance is getting near enough to worry about but currently the difference isnt your concern... low compression will make a motor hard to start as for the idling concern u have a fuel supply/delivery problem. sounds to me this motor needs a fair amount of fixing to get it right again adding oil to fuel increases the octane and puts its behavior closer to diesel than regular gas and needs higher compression to ignite most probably y regular fuel gets it to fire it requires less compression to ignite w no oil which is hard on the motor to be doing

 

[CharlieB]

Re: Hard starting mercury outboard hot or cold

You have cleaned the carbs, if the float levels are not correctly set, say a bit low AND if the idle fuel mixture is still just a bit lean, you will have starting and acceleration problems, yet once the motor is at speeds above that, it will seem to run fine.

Revisit the carbs, ensure the floats are set exactly as prescribed in the factory service manual.

Then with the boat in the water so to have the proper exhaust back pressure, and IN forward gear, readjust the idle mixtures to 'Best idle speed', this is the starting point, from here you need to further richen the idle mixture to provide the additional fuel for acceleration.

You may end up with the idle mixture screws turned out almost 1/8 turn richer than the 'Best idle speed' but it is best done in very small increments, like just the width of the screwdriver blade slot. Test acceleration/holeshot, any bog, cough, lean miss, hesitation proves a need for additional idle fuel. Make another sllight increase and retest acceleration. Repeat to perfection.