rough idle ... then eventually dies out

[ragu78]

Hi guys,

I'm looking for alittle help, this is my first boat and I don't know too much about them so any help is greatly appreciated.

I have a 1985 Bayliner Trophy with a 50 hp Force outboard, she fires up great and runs strong fully opened. It does however seem to idle really rough after running her opened up for a few and then putting her back into idle. It idles so rough that it will eventually die out, sometimes she will then fire right back up or sometimes I have to wait like 30 secs. Between shifting out of idle she gets real rough too, I messed with the idle screw (I think? the screw at the top of the carb) and that helped her from stalling between the shifting but she is still rough at idling after running her and then putting her back into idle. Could my idle screw need adjusted better? or possibly my timing is off?

Like I said I have no clue on boat motors so please decribe in dummy terms for me

 

[ck85abc3]

Re: rough idle ... then eventually dies out

Check compression. All cylinders should be over 100 PSI and each cylinder should be within 10% PSI of the other cylinders.

After low compression is ruled out. Then start looking at other things.

 

[ragu78]

Re: rough idle ... then eventually dies out

Ok how do I go about checking the compression? I believe I need a compression gauge?, and about how much will it cost? I'm pretty straped on cash at the moment.

Is there is anything else I could to do for low cost to posibly trouble shoot and eliminate other things before spending the money to check the compression? If these are dumb questions please disregard them lol, I'm new to engines.

Also if it is compression then is my engine pretty much shot? or is there a way to get the compression back up?

Thx for the reply and help ....

 

[ck85abc3]

Re: rough idle ... then eventually dies out

They are not dumb questions. I had the same questions a few years ago.

A compression tester will run you about $30 at a local automotive store. You can also call around to the local automotive stores and find one that will loan you a compression tester. You should be able to find one on loan if you live in a town with over 20k people.

Basic procedure for checking compression.

1. Warm up engine. (Make sure you have a water source for the motor, either muffs or a large container filled with water).

2. Remove all spark plugs.

3. Attach the compression tester to one spark plug hole at a time. Crank over the motor with the starter for about 5 cranks.

4. Record values.


Note, I never do this, but people on here say there should be step 2.5 Where you ground out the plug wires or something like that to prevent damage. Someone else should chime in about how to do this.

 

[ck85abc3]

Re: rough idle ... then eventually dies out

There are two other things you can do before checking compression.

1. Pull one plug at a time and check to make sure there is spark. Note what the plug looks like and compare the plug to the other plugs. If one plug is different, it might be the bad cylinder.

2. Fill a squirt bottle that mists up with gasoline/fuel mixture. After you get the motor running, spray this into the air intake. If this solves the problem, it is probably dirty carbs or bad fuel pump.



Yes, if compression is bad, your motor is prettymuch shot without a rebuild/partial rebuild.

 

[ragu78]

Re: rough idle ... then eventually dies out

Ok great, thx for the detailed help guys .... I will try these out and then report back my results.

Greatly appreciated !

 

[ragu78]

Re: rough idle ... then eventually dies out

What would be the best way to ground the plugs before testing the compression?

Thx

 

[Haywood123]

Re: rough idle ... then eventually dies out

I am sure you have adjusted the low idle adjustment over and over, but have you taking it all the way out and checked it, to make sure it isn't chipped or worn? Once you get it out, blast some cleaner though it. Probably not what is wrong, but it's free to check.

 

[jerryjerry05]

Re: rough idle ... then eventually dies out

Check for water in the fuel.Jerry

 

[jerryjerry05]

Re: rough idle ... then eventually dies out

If you haven't messed with the air screw on the top of the carb,DON"T.
If you did: turn it in until it just seats then back out 7/8-1 turn.Jerry

 

[badly bent or broke]

Re: rough idle ... then eventually dies out

My engine was experiencing the same problem and I was afraid of messing around with the idle mixture screw. When I had enough of my motor dying everytime I tried to put it in gear I followed instructions in my manual to adjust the idle mixture screw. After adjusting it, it ended up being set about where it was when I started. I then adjusted the idle speed screw so that it would run a little faster when idling while in gear and it seemed to have cured my problem. If that was the wrong thing to do, hopefully someone will chime in to tell me why it was wrong and what else to do.

 

[ragu78]

Re: rough idle ... then eventually dies out

My engine was experiencing the same problem and I was afraid of messing around with the idle mixture screw. When I had enough of my motor dying everytime I tried to put it in gear I followed instructions in my manual to adjust the idle mixture screw. After adjusting it, it ended up being set about where it was when I started. I then adjusted the idle speed screw so that it would run a little faster when idling while in gear and it seemed to have cured my problem. If that was the wrong thing to do, hopefully someone will chime in to tell me why it was wrong and what else to do.

Do you happen to have a picture of where these 2 screws are? Like I said I'm pretty dumb to engines and telling me it is near or on the carb really don't do just for me, I'd start messing with screws and soon I'll have parts falling off lol.

The engine seems to run strong and everything, and it don't always die out, but sometimes it does. Sometimes she just idles rough too. Which leads me to believe it is something to do with one of these screws you talk about. Cause Like I said I messed with the screw on the front top of the carb and she idled alot better and seems to stay idling longer but still idles rough and dies out every now and then.

I really appreciate everyones input on this and it is greatly appreciated ....

 

[maxum247]

Re: rough idle ... then eventually dies out

Are you sure it's running on both cylinders at idle?
Water in tank?
Too much oil mixed in gas fouling plugs?
Old dirty gas?
When was the fuel pump last rebuilt?
Decarb the engine, put in new plugs and see how it runs.

 

[shrimpman123]

Re: rough idle ... then eventually dies out

check for water in your gas tank, and also in the fuel filter, most all tanks will sweat and cause condensation inside the tank.it will settle to the bottom of the tank and the bottom portion of the carb and the filter also,the boat moving around will, jostle the fuel up and cause some of the water to be pulled into the fuel flow and cause many rough idle, mid to high end skips and and all sorts of little stumbles as well. these type of little things are what YOU can look for first ,before bringing it to say, my shop,,and are usually cheap and fix many problems.check these things before ever moving any adjustments on the engine,adjustments dont move by themselves and were correct at one time.although they do need moving sometimes its just not the first thing to do.

 

[ragu78]

Re: rough idle ... then eventually dies out

Are you sure it's running on both cylinders at idle?

Again, I have no clue about engines ... how would I verify this?

Water in tank?
Too much oil mixed in gas fouling plugs?
Old dirty gas?

Could be, bought the boat with 2 full tanks of gas and dont know how long it was sitting. I'll know for sure Friday cause I'm taking her out and need to re-fill her up. I also put 2 new plugs in her before the last 2 times I took her out and there fine looking and both look burnt same.

When was the fuel pump last rebuilt?

Not sure, I gonna buy the rebuild kit from here if it is avaliable for my engine .... ?

Decarb the engine, put in new plugs and see how it runs.

Yes, I plan on decarb'in her this weekend.

 

[maxum247]

Re: rough idle ... then eventually dies out

You'd need to check for a good blue spark on each spark plug, use the search feature at the top of the page and type in (spark check) or something simular like (cylinder not firing), this will bring up different things that may be helpful!

 

[ragu78]

Re: rough idle ... then eventually dies out

Oh duh .. my bad ... sparks good while idle too.

Fuel filter was just rebuilt, brand new ....

one thing I did notice was I ran it in a bucket today well checking out my new home made telltale and I noticed it seem like a lot of mixture was in the bucket after I was done. Is this common? If not could a bad seal be causing my rough idle and rough shifting from ilde to in gear?

I also read that someone said there telltale shot damn near 8-10 ft, mine is only shooting like a foot? Will it shoot further when she's in the lake? or is this a sign that my water pump is going bad?

Thx

 

[ragu78]

Re: rough idle ... then eventually dies out

I know this topic is old already but since I was a real newbie at the time (heck still am) than I figured I better post my fix for any other newbies that might run into this problem .... DON'T LAUGH GUYS ! It turned out to be bad gas ..... dumbed the old gas and put new gas mixture in the tank and boom .... running fine now with no stalling or putting. Hope this may help someone out.