wont idle

[picklefish]

hello all, Here goes i have a 75hp,757hb chrysler outboard. went out on lake ran perfect for 25 minutes we lost all power. i looked under hood the middle spark plug wire melted to the block. the only way to get it started was to adjust the idle screw on the carb. which ran at half power about fifteen minutes then died and now wont idle. it does start but wont idle or stay running longer than a few minutes. i did change the wires. i may have tiny water droplets on spark plugs. my manuel says that might be from running to rich. im pretty new to the whole outboard but im good with my hands. i could use some help i cant afford to screw something up.

 

[jerryjerry05]

Re: wont idle

NO IDLE SCREW!!!
That's an air/fuel adjustment screw.
Turn it in till it just bottoms out,then out 1 turn.
Leave it there till you figure out what's wrong.

Then do a comp test.
Sounds like it overheated????

Check the impeller?
Check the thermostat?
Its a 75 75hp.

 

[picklefish]

Re: wont idle

thank you for the start. I will get on it today.

 

[Jiggz]

Re: wont idle

A melted spark plug is a sure sign of serious overheating which probably means the piston and cylinder are probably in need of repair. Do a compression test and if unsatisfactory, remove head and inspect. The reason it won't idle anymore is probably because not all cylinders are firing.

 

[picklefish]

Re: wont idle

i did a compression test. #1 150 #2 30 #3 40. so i will be removing the head cover tomoro. i will keep you guys posted. thank you again all.

 

[picklefish]

Re: wont idle

well i have a bad head gasket. everything looks good inside. waiting on a new gasket before i can put back together. any tips on what appears to be a simple process?

 

[SkiDad]

Re: wont idle

make sure you torque it to the correct INCH POUNDS. You need a special torque wrench for inch pounds. Sometimes people confuse inch pounds with foot pounds. If you torque too high you will snap a bolt or strip a hole - the block is aluminum.

 

[Nordin]

Re: wont idle

Another very imported thing. Retorque the head after you have run the engine about one hour (warm), if you put a new headgasket in.
If not you will blow it again.

 

[Jiggz]

Re: wont idle

And finally you cross-torque starting with the 4 inner middle bolts, 4 outer middle bolts, back to 4 inner bots and then 4 outer bolts and so one. There is actually a sequence for proper torquing. Maybe someone in here can post a pic.

 

[jerryjerry05]

Re: wont idle

20 ft#s is what you tourqe it to.
No sillycone .
Make sure the surfaces are CLEAN!!!

Now fix the impeller or figure out why it got hot?
Change impeller and check the thermostat.
Don't think you have to worry about salt water corrosion in that area.
How clogged up is the spaces around the pistons??Pics??

 

[picklefish]

Re: wont idle

here is one pic. i will check thermostat and impeller.i also picked up the exhaust plate gaskets and the gasket for the little extra water bypass valve bottom left of the exhaust plate.and all of your input very helpful so i thank you all.

 

[jerryjerry05]

Re: wont idle

The exhaust plate and the little relief valve are gonna be TRICKY!!!
They will probably break so start slow.

Use PB Blaster a Hammer and probably heat.
I spray,tap and heat,repeat again and again.
Then try loosening.
The tiny screws on the little cover,DON"T touch.
You can bet they are gonna break.
Too much heat and it will melt the aluminum around the threads,
Be VERY careful!!!

Did i mention take your time and spray,tap,heat.SLOWLY!!

 

[Jiggz]

Re: wont idle

The condition those cylinders are in indicate a serious need of de-carboning.

 

[picklefish]

Re: wont idle

can one of you guys recomend the best cleaning agent to use on that carbon?

 

[jerryjerry05]

Re: wont idle

I like Mercurys Power Tune.
Any Mercury dealer.
Even a lot of marine stores carry it.
Some here like Seafoam.
Some use water as you run it??
I wouldn't do that.
Get the gasket back on and run it for a while,you want to seat the gasket.
Make sure the carbs are set right.
Inital setting one turn out from lightly seated(air screws).
I get the motor hot,then spray PT in the carbs.
A little at a time.
Then as it starts to burn and smoke I spray in a bunch,stalling the motor.
Then tilt the motor up and remove the plugs,spray more PT in each plug hole.
Let it set for 48hrs.
Clean the plugs and start.Run for a while.
Then do it again.

 

[picklefish]

Re: wont idle

i also have a 2 piece cylinder head. i cannot find a gasket for the outter piece. there looks to be that make your own gasket. is there a special kind i need?here is a pic.

 

[jerryjerry05]

Re: wont idle



That can be fixed with silicone.
I like black cause the other colors stickout too much.

 

[picklefish]

Re: wont idle

finally got my head gasket and put it on. i want to give the silicone a little more cure time before i fire it up.

 

[emoney]

Re: wont idle

We'll expect pictures at the very least, but would prefer it in video form.

 

[picklefish]

Re: wont idle

sorry for the camera work. but she actually fired right up. she sounds a little different on video but she is running good so far not sure if ill have a chance to take it out this year got real busy. now i would like to thank all of you guys for the expert tips im sure this is not the last you hear of me lol.