1994 40HP Evinrude - WOT problem

[Loon]

I have my motor attached to an 18 foot Princecraft. The engine works fine at Idle and up to 3400 RPM. It seems that when ever I attempt to go past 3400 RPM it drops back to 2400 RPM. If I give it full throtle from dead stop it will get to 4000 RPM before it settles back to 2400 RPM. I have done the link and sync routine on it. I have checked for good spark and have run the cylinders individually to confirm operation. I have the repair manual and it talks about the power pack having an auto limiter on it. Could the power pack be malfunctioning? I would really like to have a good idea before I go and spend 200.00 on a new power pack. Is there anyone out there that can offer some advice. Thank you.

 

[rwise]

Re: 1994 40HP Evinrude - WOT problem

Loonie<br />Welcome to I-Boats. give the modle number of your engine and you should get more responces. Is the bulb in the fuel line hard when this happens or soft. if its soft can you pump it and get more rpms? don't know about your's haveing a rev limiter<br /><br />anyway "bump" back to the top

 

[ED21]

Re: 1994 40HP Evinrude - WOT problem

I know my '89 40 hp has a SLOW system to limit revs if the engine overheats.<br />It sort of sounds like it is kicking in.<br />Maybe the overheat sensor is bad.<br />I would have to check manual to get more specific.

 

[Looniator]

Re: 1994 40HP Evinrude - WOT problem

Sorry Guys, the Model is 40TE, and is fitted with S.L.O.W., I discovered an air leak in the fuel line and have repaired that and replaced the bulb just to be on the safe side, arrow is in the right direction. However, the problem remains. I did try pumping the ball and it had no effect, so I have ruled out the fuel pump. The bulb didn't get right hard but it didn't stay soft either. This is my 4th day with a boat so I have limited experince in how hard it should get. I was talking to a firend of a friend today and he suggested as well that it might be the power pack as the power pack has SCRs and if one of them goes it would effect the RPM limit. The SCRs are packed in epoxy so they are next to impossible to replace. The RPMs always drop off at around 3400 unless I gun it then it will peak at 4000 before it slows down. I was considering replacing the thermostat however I don't believe this is the problem because it always seems to kick out based on RPM and not any sort of temerature. The manual says that the power pack has an RPM counting and limiting circuit to protect the engine from damage due to severe overspeeding. Anyway, what do you guys think. Appreciate the help.

 

[McGR]

Re: 1994 40HP Evinrude - WOT problem

If a power pack SCR was bad you'd lose spark to one cylinder. It's doubtful you'd get beyond a couple thousand RPM on a single cylinder. So I doubt the ignition coil driving SCRs are in question. Nontheless, there could be other issues within the power pack causing your problems. But first I'd rule out the fuel system. When was the last time the carbs were cleaned or rebuilt? It's possible you're starving for fuel at high speed. If a couple depressions of the primer switch at full speed causes the motor to take off you know you have a fuel issue. Carb kits are cheap and rebuilding those carbs is easy. You may want to consider doing this before dumping $ into a power pack.

 

[Looniator]

Re: 1994 40HP Evinrude - WOT problem

I tried the Primer check and the manual says that if I depress the primer when at 2000 rpm then the engine should drop to 1000. The engine responded as described in the manual. The carbs were cleaned 2 years ago and has hardly been used.

 

[rwise]

Re: 1994 40HP Evinrude - WOT problem

it would not hurt to clean the carbs, just might fix it, if it doesn't then look to the p-pack. setting can stop up some of the circuts in the carb make sure to get all the tiny pasages.

 

[Looniator]

Re: 1994 40HP Evinrude - WOT problem

Okay, after reading your email for a second time, I wnet back out and went WOT and pressed on the primer. The thing took off like a bat out of hell. So I guess it is a fuel problem. I replaced the fuel connection to the engine and I ended getting an extra 200 revs out of it before it idled back to 2800. Must have had an air leak with that connection. I also did a complete visual of all fuel connections and noticed clips missing of the upper and lower carbs so I put them on. I also removed the top carb disassembled and reassembled it. It was in mint condition. The previous owner must have had them rebuilt before I got it. Any more suggestions.

 

[Looniator]

Re: 1994 40HP Evinrude - WOT problem

Is it possible that my anit sypon valve in my tank could be causing me this problem?

 

[Loon]

Re: 1994 40HP Evinrude - WOT problem

Okay, Just so other newbies may follow with what I have done to try and correct my problem I am providing an update. Once it was determined that I had a fuel problem I did all the cheap stuff first, fuel filter etc... Then I got stupid, removed the top carb and found it in excellent condition, as eluded to in earlier posts, and figured that the bottom carb was in similiar condition, so I left it were it was. Now I am told that if one of the carbs is going to give me problems then it would most likely be the bottom one as any fuel left in the system would drain down to the lower bowl and sit there. So now I am back to removing the carb again. I will let you now how I make out. The old adage applies in this case....There is never enough time to do the job right the first time, but there is always enough time to do the job right the second time.

 

[McGR]

Re: 1994 40HP Evinrude - WOT problem

Loon:<br /><br />The carbs can look beautiful externally and nice and clean down the throats but can still be in bad shape internally. Ideally you should rebuild the carbs. But if your stuck for time/money or whatever, at least clean the high speed jets. They are located behind the bowl drain screws at the bottom front of the carbs. Techincally a special tool from OMC should be used to remove these. But, if you are creative with an old screwdriver and a grinder you should be able to fashion something that works. Anyway, just unscrew the jets and clean out the orifaces. This will very likely fix your problem.

 

[Loon]

Re: 1994 40HP Evinrude - WOT problem

Whooo Hooooo, I got it. I took out the lower carb and removed the bowl. First thing I noticed was that the High speed jet gasket was missing. Cleaned it while was apart and install missing gasket. Got 5300 RPM on rough water with it. Thanks for all your help guys!