2006 115ELPT4S running rough at low speed, fine at high speeds

[pikie]

Third trip out this year and my outboard started running very rough at low speeds. I took a video, and its hard to see/hear it until I go a little faster but it really can be felt cutting power when at low speeds. Going fast its fine.

I've had this boat since last summer, and haven't had any trouble with it. I replaced the fuel filter/water separator and changed the oil/filter and lower unit oil myself last fall. The inline filter inside I did not end up changing since the replacement ones I bought did not fit right (but it looked clean).

There is a little sheen of oil present since I did the oil change, but I think its because I spilled a bunch when I changed it and cleaned it up as best I could. No gas smell to the sheen.

Here is a link. I tried to show the oil pres/rpm guages...It looked like the oil pres guage dropped off some during the problem. At high speeds, oil pres is steady.

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photos.app.goo.gl

Thanks for any advice/help you can provide.

 

[pikie]

I talked to the service mgr at my local dealer, he suggested changing the internal fuel filter. I did that, but no luck. I'm going to see how hard it is to change the fuel pump next. It feels fuel system related to me.

 

[racerone]

Check availability of a new high pressure pump.-----Or perhaps have dealer check fuel pump output pressure.----Check lift pump as well.

 

[pikie]

I ordered a new fuel pump for it. Its the easy one to change replacement part 804249TI. Are there more than one fuel pump on theses?

 

[pikie]

I ran the boat this weekend and the problem changed a little, its now also dogging when trying to go full throttle. I can have the throttle where I know it should be going about 30 mph, but its running rough and only going about 20 mph. If I wait a while all the sudden it will kick in and run normal and go 30 mph. I put a new fuel pump in yesterday and no change. Time to look into high pressure pump and lift pump? Getting it into an actual dealer is very hard where I live, but is possible if I can loose my boat for at least a month.

 

[butlp]

I ran the boat this weekend and the problem changed a little, it’s now also dogging when trying to go full throttle. I can have the throttle where I know it should be going about 30 mph, but it’s running rough and only going about 20 mph. If I wait a while all the sudden it will kick in and run normal and go 30 mph. I put a new fuel pump in yesterday and no change. Time to look into high pressure pump and lift pump? Getting it into an actual dealer is very hard where I live, but is possible if I can loose my boat for at least a month.

If you haven’t already, I would replace all the fuel lines, replace the LP pump, clean the VSC chamber and check the ridiculously expensive rubber sleeve on the output of the HP pump. I had a similar situation and it was caused by the ethanol in the gas wrecking the fuel lines.

 

[pikie]

Update: I've replaced all gas lines from tank back all the way to the low pressure pump. I inspected the fuel pickup and it looked clean and no issues. I've also installed new spark plugs. The old ones looked a little whitish, which I hear means its starved for fuel (which makes sense).

The gas gauge never worked right, so while I have the deck up, I've ordered a new sending unit and gauge, since I got very strange/inconsistent resistance readings out of the original sending unit and could not get the gauge to do anything at all in a bench test.

I did run it on muffs in the driveway and it sounded better, but I won't know for sure till its all back in place and I'm back on the lake. I also bought a fuel pressure test kit that I can try on the high pressure side to see if my problem is in there...if it is, that probably means time for professional help.

 

[pikie]

Fixed! Thx for the help! Either new gas lines or new spark plugs fixed it.