1989 90hp V4 Evinrude rough idle

[Dennisanoka]

The egine seems to run smooth at all higher RPM's and plugs run dry and light brown, but at idle speeds 3 of the 4 plugs run very wet and is a bit rough. Clearly one of the plugs runs pretty dry even at idle. If after running at idle, I open it up, it runs a bit rough but then clears out and is smooth again.

 

[tashasdaddy]

Re: 1989 90hp V4 Evinrude rough idle

have the carbs ever been clean and rebuilt, sounds, like a fuel restriction in the low speed jets. cylinder running lean at idle, means no lubrication, thus can damage cylinder walls, and rings. also have you done a compression check. i have the same basic engine 1988

 

[Dennisanoka]

Re: 1989 90hp V4 Evinrude rough idle

Yes I have done a compression check and all measure in the low 100's. I have had the carbs off and checked the float levels which were correct and replaced the main body gaskets. I have not totally rebuilt the carbs. I have noticed the engine voltage at idle is at just 12.0 volts but at higher RPM it is 13.1-13.2 is this disparity normal? Are wetish plugs completely normal at idle? Since I am also now bypassing the VRO, will the engine run a bit more rough at idle now since the mixture is 50:1 rather than 100:1?

 

[tashasdaddy]

Re: 1989 90hp V4 Evinrude rough idle

the engine should run just fine on 50-1, as mine is an 88spl which is the 90 without vro. volts are fine. sure sounds like you need a carb cleaning, including the high speed jets, and rebuild kits. also has any one messed with the link & sink.

 

[Dennisanoka]

Re: 1989 90hp V4 Evinrude rough idle

Since I did have the carbs off I did do my best to re-set up the link and sync as best I could following the manual but I still wonder if this could be part of the issue. Have you gone thru the procedure and if so do you have any tips? Or another recomended procedure other than the one in the manual? It is a neigbors manual so I don't have it readily at hand.

 

[Dennisanoka]

Re: 1989 90hp V4 Evinrude rough idle

BTW, when I had the carbs apart I considered replacing the floats but didn't and ever since I've wondered if they in fact do need replacing, possibly having lost some buoyancy over time and then give the appearance of being set up properly, but when the float bowl fills they do not rise to the proper level. As you can tell I am really scratching my head. I'd just take it in to the shop if I had confidence that it would come back fixed.

 

[Dennisanoka]

Re: 1989 90hp V4 Evinrude rough idle

I have rebuilt both carbs. The rough idle has gone away. The only issue I am wondering about is that 3 of the plugs have a wet look after idling and 1 is dry. The dry plug is not light grey or white(lean), it is still brown. So is one dry plug a reason for concern? All 4 are dry after a high speed run. So is this one drier looking plug something to worry about as long as it is in the brown range for color?

 

[Dennisanoka]

Re: 1989 90hp V4 Evinrude rough idle

Tashasdaddy or another,

Is there anyway that you could tell me the the exact size of the screw/bolt that holds the fuel fiter in place? As you know there are two- length/ thread type etc. I am going to the SPL fuel pump and need to be sure of thie size.

 

[Dennisanoka]

Re: 1989 90hp V4 Evinrude rough idle

Sorry-I need the screw/bolt size for the fuel pump not the fuel filter. (up too late I guess)

 

[Dennisanoka]

Re: 1989 90hp V4 Evinrude rough idle

BTW I should mention this issue was resolved in another post. The problem was the VRO fuel pump side was leaking fuel back down into the #4 cylinder thru the crankcase pulse hose. This was brought to my attention by helpful people here on this forum. I have replaced the VRO with the 88spl fuel pump but I need to find out the correct screw size for the mounting screws. I don't see them called out in the diagrams. I hope someone might know.

Thanks

 

[tashasdaddy]

Re: 1989 90hp V4 Evinrude rough idle

try #10x20 stainless.

 

[Dennisanoka]

Re: 1989 90hp V4 Evinrude rough idle

Thank you very much!!! I'll get two today.

 

[Dennisanoka]

Re: 1989 90hp V4 Evinrude rough idle

The scews were #10 x24 but I figured that out at the store since they didn't have #10x 20. It's ok cuz you got me on the right track. At the top of this post I mention rough idle and that was fixed with the new fuel pump. But I believe there is still another issue going on as well which I am not comfortable ignoring. The #1 cylinder is much leaner than the other 3. By comparison after a 5 minute idle 2,3 and 4 have wet electrodes but are not fouled. I suspect that is normal since I am now mixing 50:1. But # 1 is dry as a bone. Since I first made this post I did rebuild the carbs with the usual carb kit. I did not soak them as some suggest but I did throughly blow them out with compressed air. So the floats, both gaskets, needle valves were replaced. I also swapped the low speed jets which are accessable on the top front of the carbs just to see if it would change. Too lean at any RPM is dangerous to say the least. I would sleep alot better at night if I could nail this one down.

 

[Dennisanoka]

Re: 1989 90hp V4 Evinrude rough idle

I have decided to start a new thred for this lean condition since it is really a different issue and is no longer a rough idle. It will be called One lean cylinder.