Neutral idle rpms have decreased over time

[Bassman42]

I have a 1997 evinrude 115 with a remanufactured powerhead. E115eleua, with the new block I got a new fuel pump, spark plugs, water pump, and rebuilt carbs. Upper linkage is adjusted correctly. And just a hint nothing has been touched or adjusted since I got the new block. From the first run in late march til currently the idle rpms in neutral have decreased over time. It's set(according to the shop who did the work) at 1000 roughly, maybe a little less, in neutral, right now it's only hitting about 600. Both ignition coils were replaced too. Any ideas? Compression 120 on all 4 cylinders

 

[BrettNC]

Here is what I would check for - Loose timing adjustment screw throwing off timing, double check all linkage, check cylinders for water in them. Does the motor still idle in gear?

 

[BrettNC]

This could also be a symptom of a new motor that is breaking in. If it still idles fine in gear and performs correctly then you are probably fine.

 

[PhrozeN_FisH]

One of the first things I look at is the cam follower roller on the throttle lever and the roller assy. on the carb. Inspect to see if the outer layer has cracked and fallen off which would account for lower idle speed. It could also affect full throttle rpm's as well.

 

[Bassman42]

It does idle in gear, I thought it was just the new motor breaking in as well, the only thing that bugs me if I try to gun it the motor bogs down and dies. Thats only if I go from idle to full speed ahead, when I just do it normally then it's fine, I gun it when we're tubing and I can't fling anyone if I hit a big wave in idle and then gun it. Anyone who knows how to tube knows this is a good way to do it! Lol

 

[interalian]

If anything, I'd expect a motor to idle higher as it broke in, all else equal. Less friction.

 

[Bassman42]

So you're saying this is normal? The idle has gotten a little rougher so I'm expecting a possible dirty fuel filter or maybe a little trash in the carb? I've got a can of seafoam I'm gonna run through. The fuel filter has about 50-60 hours. The motor only has about 30, this is my second reman powerhead, the first one they put on in february had a mechanical issue with the top two pistons. There's a stamp on the pistons that label port and starboard, well the top two were flip flopped and it wouldn't run. They replaced the whole thing free of charge. And after that it has run like a bat outta hell

 

[BrettNC]

The reason they might idle lower as they break in is that suction at the bottom end of the piston increases, pulling more fuel out of the carbs. The engine doesn't run as lean. If you are idling in gear at around 600 rpm, that means there is very little drop in engine speed between neutral and in gear. That means the motor has the power to easily handle the extra load when placed in gear. This is good.

Stalling on quick throttle changes is indicative of a lean condition. Check fuel delivery, carbs, and gasket leaks.

 

[Bassman42]

I will check for this! Thanks

 

[oldboat1]

I don't think it's remarkable that fine tuning would change over a four or five month period, particularly after break in (and during some regular use, presumably). If the carbs were to be adjusted a bit leaner now, for example, the rpms should come up to 1K and idling would likely smooth out again. I would not run decarb solvents through a newly rebuilt motor (not clear what the purpose would be -- what's thought to be dirty?) Think I would ask the folks who rebuilt it for their suggestions -- keep up a conversation with them.

 

[Bassman42]

Well the only reason I was going to run cleaner through it is because when block shot all to hell 2 years ago, it had a full tank of gas. Which sat til feb this year, and no I did not run that gas, but I figured it got gummed up in the tank itseld from the old gas. The idle has gotten more rough too. I also have gas leaking into the air box silencer and down into the lower cowling.. Which has happened since I got it back and the shop told me it was nornal. All hoses are connected to the box as well. Do y'all think that's normal? I won't adjust the carbs cause it's already running lean evidently if ii gun it and it tries to bog down.. If I can clear that out then I can try to adjust them. But what about the gas coming into the airbox?

 

[Bassman42]

The reason they might idle lower as they break in is that suction at the bottom end of the piston increases, pulling more fuel out of the carbs. The engine doesn't run as lean. If you are idling in gear at around 600 rpm, that means there is very little drop in engine speed between neutral and in gear. That means the motor has the power to easily handle the extra load when placed in gear. This is good.

Stalling on quick throttle changes is indicative of a lean condition. Check fuel delivery, carbs, and gasket leaks.

Yeah it's definitely running a bit leaner then normal.. I pre mix because the vro fried the motor a long time ago, so now I do it on my own. I have noticed that I've been off my measurements by about 2 fl oz, I always just fill with 6 gallons and add a pint of oil, but each time I'ce apparently only been putting in about 13-14 fl oz.. Too long to explain how I learmed this lol, would adding less oil like that cause it to do that? As soon as I added a bit more it went away. Plus I went from that cheap quick silver oil to the evinrude xd 30