Engine runs great once I get it idleing...

[cmbksu]

Hi all,

I have a 1997 Mercury Force 90HP Outboard. The motor runs great at idle and full throttle once I get it running. The problem is everytime I shut it down for a while, it doesn't want to idle when I start it back up. I usually end up starting it several times, trying to throttle up as soon as it starts and eventually it will rev up and is good after that. It does smell like it is burning rich after doing this but I am assuming that is because of the multiple start attempts? Boat shows none of this behavior when running on earmuffs in the driveway. Purrs like a kitten. I had a mechanic look at it but he said without seeing it behave under load (in the water), he did not know what was causing it. He said it ran "perfectly".I am going to try putting a can of seafoam in but I would love any thoughts you may have.

 

[Jiggz]

Next time you have the same problem while in the water, try removing the cowling and see if the motor starts easily and idles perfectly. If it does, you could have an exhaust leak in the engine compartment or cowling.

 

[cmbksu]

Ok... Thanks for the advice

 

[cmbksu]

I forgot... Last year when trying to figure it out, I had the cowling off when trying a little starting fluid in the carb but no change.

 

[HotTommy]

I'm sorry jiggz elegant solution wasn't the right answer. I liked it a lot. .... Here's what I think you said. Correct me if I understand it wrong.
1. On a cold start, it will crank and fire briefly, but die before it can establish an idle.
2. You can sometimes get it to run by adding throttle just as it fires.
3. If you shut it down and immediately start it again, it will idle and run.
4. If it sits for a while, it acts like the cold start in 1 above.

You didn't say, but I assume you are using the FAST IDLE feature and the choke/enrichment for the starts. If you are not using full FAST IDLE, try that first. If you are using both FAST IDLE and enrichment when the problem occurs, I have a theory. I suspect the fuel enrichment is giving you enough fuel for it to fire, and immediately advancing the throttle sometimes works because it opens additional fuel circuits in the carburetors. I suspect your idle fuel circuits are clogged and not providing sufficient fuel for a normal start. That is why starting fluid helped out. If my theory fits your situation, the solution is to remove and clean the carburetors. Its a common job for these engines.

Disclaimer: I don't know nearly as much about these engines as many of the old heads here. You may want to wait to hear what they say before you act on my advice.

 

[cmbksu]

Tommy,

Your interpretation is spot on. I will show my ignorance now. I use the enrichment feature but do not know anything about a fast idle. Can you explain this to a novice?

 

[HotTommy]

On my throttle quadrant there is a lever beside the throttle that lies flat and out of the way until you need it. To use it the main throttle has to be in the neutral, idle position. I can then raise the fast idle lever up to effectively raise the idle speed of the boat on a cold start. It can be raised part way up or all the way depending on how cold your engine is.

I'm not often successful posting pictures, but maybe you can cut and paste this if it doesn't show up:
http://forums.iboats.com/filedata/fetch?id=7194091&d=1389052253

 

[Jiggz]

OK, now I understand the problem. But when you mentioned that it purrs like a kitten at the driveway on muffs it tells me also the idle setting might be too low for in water operation. Make sure the idle mixture settings are set at least 1 turn out from fully seated and the idle setting is at least 800~1000 rpm neutral in water and 700-900 rpm idle in gear. And yes, after initial cold start a properly working engine that is warm would easily start even without the enrichment or fast idle.

 

[cmbksu]

Thank you both... I am going to hit it with seafoam first and run the crap out of it. If that doesn't work, I will clean the carb. I am going to stay away from an idle adjustment for now because it does idle perfectly once I get it running but I will make sure that the RPMs are correct. Never called it a fast idle (once again, I am a novice), but I now know what you mean. My fast idle is not a lever but a button you press in that allows you to throttle w/o engaging the prop. This is what I was refering to when I said "throttle up".

http://forums.iboats.com/filedata/fetch?id=7168765&d=1341605711