Strange problem

[swfl_fishin]

I have a 1987 Evinrude 30hp that was completely rebuilt before I got it. It is a very clean motor and generally runs great. Strange problem is that it idles fine and runs really good above 2K RPM, but it hesitates between 1500-2000 RPM. Even then, it only seems to do this while under load. For example, if I have the garden hose hooked up to it and flushing it, I can adjust the fast idle to that range with no problem. When on the water, totally different story. It chokes in that RPM range. I have been following the troubleshooting path of fuel, and have taken these steps: 1. New gas with Lucas treatment in it. 2. New water separater. 3. New inline filter.

Any suggestions would be greatly appreciated.

 

[ezeke]

Re: Strange problem

You should never run that motor over 1500 RPM with no load.

 

[tashasdaddy]

Re: Strange problem

agree^^^, if this does not work, then possible clogged high speed jet.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[JohnnyRuuDe]

Re: Strange problem

You should never run that motor over 1500 RPM with no load.

Does that go for my 88 Johnson 40hp also?

 

[ezeke]

Re: Strange problem

Running any two stroke at high RPM with no load is risky because of the possibility of a runaway.

 

[Wildcatin]

Re: Strange problem

What does runaway mean?????

 

[Mas]

Re: Strange problem

What does runaway mean?????

Without any opposite force (such as a prop spinning in water) to make the motor work, the motor can possibly continue to increase in rpm...bad! It's almost like a car on a hill without brakes!

MAS

 

[swfl_fishin]

Re: Strange problem

So you think it is just a carb adjustment? Strange that it runs fine above 2K RPM. I have never run the motor above 1500 RPM without load. Sorry if my post was confusing. When I said 'that range', I was talking about the lower end of the range where I'm having a problem (which is 1500 RPM). Honestly, I wish I never had to run the motor between 1500 and 2000 RPM, but we have SO many slow and manatee zones around here, I don't have a choice.

 

[mthieme]

Re: Strange problem

I have a neighbor up the street that has an older 6 hp Evinrude. It has a very similar problem. He came down last fall seeking assistance adjusting the carb. Everything was rebuilt. He didn't know it though as he recently got the setup. I noticed every screw and gasket underneath the cowl had been turned adn replaced. Needless to saw, he has more issues than a simple carb adjustment. Sorry to be cynical, but total rebuilds always send up a red flag with me especially going in completely cold.
Can you tell us what exactly was "completely rebuilt"?
Does this include the fuel pump, carb itself, etc.?

 

[jay_merrill]

Re: Strange problem

You say that the motor "hesitates" between 1500 and 2000 rpm - what do you mean by "hesitates. Please elaborate.

 

[swfl_fishin]

Re: Strange problem

You say that the motor "hesitates" between 1500 and 2000 rpm - what do you mean by "hesitates. Please elaborate.

I guess I mean it chugs like it is going to die. It doesn't die though, and if I throttle up to 2k RPM or higher, it runs just fine.

 

[steelespike]

Re: Strange problem

Chugs to me is sort of Duga-duga-duga sort of shuddering.Sometimes called 4 stroking.A lean stumble is allmost like it shuts down relatively smooth but guttless.Losing one cylinder it applys relatively smooth power but not very effective.
Carefully adjust low speed screw warm in gear unrestrained idle speed about 750.Leave it slightly on the rich side.Check for any air leaks listen with a piece of hose or spray WD40 on suspect areas.

 

[swfl_fishin]

Re: Strange problem

Update to the problem....thus far, I haven't done anything to troubleshoot or correct the problem. On my last two trips out, the problem has gotten worse, in that now it is doing the same thing between 3500-4000 RPM. Is the general consensus still carb related?