Rough Idle

My '86 E-XP150 has been pretty hard to keep at an idle speed. The RPM's seem like they might be just a tad low, maybe 800rpms +/-. I know I've seen where it should be, but I don't recall.

The boat generally starts easily, but if I leave it idling long, it dies. This past weekend, the boat started up, then in the time I went to unhook from the trailer until the time, I came back to pull off, it had died. It was extremely tough to start after that. It might fire, but when I'd go to shift, it'd die out.

When it finally starts, it runs great. It even seems to idle better when it's warm and after it's been running a while. I shut the boat off several times during the last outing and it never was as tough to start as it was when I was trying to get it off of the trailer. I'm not sure if that was because I ran that fuel tank down fairly low the time before or if something else was the culpret. I fueled up prior to this trip to the lake. I swicthed tanks and it did start easier, but both tanks were left in the same state of nearly empty after last outing. Again, both were topped off, before this outing.

I had rebuilt the entire P.H. last year and it was running great. L.U. then went to the shop because of a shifting issue. They rebuilt L.U. and linked and synced the PH. I just got past the 10hour mark on the L.U. about 2-3 hours ago. I have called the shop, they just said bring it in and leave it. They are about 14 days behind right now.

I don't recall the idleing issue last year, but that was 8-9 months ago. I plan on pulling the plugs and cleaning/replacing, but I'm curious if that would be the problem. Early in the season, I thought it was the colder water, which was about 60*. The water is currently 70* and it's still acting the same if not worse.

Is it possible my choke is going bad or what would you check? I thought about just turning up the idle, but don't want to screw anything up.

Sorry, for all the info, but I want to provide as much info as possible. Should I let the shop figure it out, since they linked and synced it. Should I clean the plugs and try again. What about turning up the idle speed screw?

Re: Rough Idle

Been like that since you got it back from the shop?
It's fouling the plugs? all six look the same?
Is that fixed jet or adjustable carbs - could just the idle speed mixture.
Why are you thinking that nearly running the tanks dry would be a problem - is there some debris in there, might have plugged up an idle jet or two?

Re: Rough Idle

I don't really recall it being like that last year after I got it back, but like I said, that's been almost 8 months or so. I can't really recall. They had me do a break in procedure, similar to breaking in a PH. It wasn't until this spring that I was able to run it much at all.

I hope to pull the plugs tonight and look. Haven't pulled them yet. Keeps raining so I keep covering the boat.

The shop didn't touch the carbs internally, I did however clean them very well when I rebuild the PH and it ran great after that. Except for the final timing. I really have a feeling that all the idleing of the break-in, fuel stabelizer and some trolling while fishing might have carboned up the plugs a bit. I'll pull them check them, clean them and probably run some seafoam in the tank to clean things a bit.

I don't really think running the tanks nearly empty would cause this, but I did find it a bit odd, that when I finally switched to my other tank it finally started ok. Maybe I should replace the fuel line on all tanks, just in case one of them is going bad. I doubt that's the cause, but fuel line is relatively cheap. I just kind of thought, maybe if the tank was almost empty (1-2 gallons of fuel left in a 12 gallon tank) maybe the line drained or something and was having trouble pressurizing.

There better not be any debris in there either. I am picky about the fuel I put in my boat. I'll also pick up another water-seperator, maybe it's going bad. I don't have much time on the current one, but I haven't done that this year.

I'll pull the plugs tonight and post the findings of those. Maybe I'll take a picture as well....

Re: Rough Idle

You may also have a fuel pump on its way out. Might work great once driven by high rpm pulses and not work well at all in the low range. Try pumping the bulb when it gets finicky at idle. At least you'll eliminate it as a possibility.

Re: Rough Idle

iwombat said:

You may also have a fuel pump on its way out. Might work great once driven by high rpm pulses and not work well at all in the low range. Try pumping the bulb when it gets finicky at idle. At least you'll eliminate it as a possibility.

Click to expand...

I'll try that, but it better not be the problem as it is a new fuel pump purchased when I rebuilt the PH last year.

I will try that though...

Re: Rough Idle

If it's new then I doubt it's an issue. Still, always good to eliminate things as problems and go from there.

Re: Rough Idle

Who rebuilt the power head, you, or a dealer? Those carb's should have been rebuilt with new kits', not just cleaned. It should also of had a new water pump, along with thermostat's. If you know the engine is sound, I would retrace my step's with another sync. & link. Were the carb. lower, and mid-range jet's kept in there proper order?

Re: Rough Idle

Opp...my bad...I read that as a merc...so deleted my earlier response.


But if the carbs were rebuilt without changing at least the o ring gaskets on the inside of the carb the motor will run like you say. For some reason they can't be reused as easy as standard gaskets. You may want to also check the tiny plastic grommet that keep the carb links attached to the carb plates. They will give you fits if one pops out...and old ones tend to do that. Those are the easy and simple carbs to work on.

bp