Weird problem with 30Hp Johnson (early 90's?) PROBLEM FIXED

[smithdt]

I hope someone can help me with this...

I replaced an early 80's 35Hp evinrude with an early 90's 30 hp johnson about 2 years ago. It's done very few hours and always in fresh water. It been fine up until a few months ago.

It still starts well, even after long layovers. It also runs well at speed, getting on the plane fairly quickly (Although suspect it may be undersized for the hull - see my profile- but that's a thread for another day..)
The problem starts after about 2-3 minutes of running on the plane it just cuts back to idle and will not rev above idle until it's been sitting on idle for about 2-3 minutes. It then runs fine for another 2-3 minutes and the whole thing starts over...very annoying

I discussed this with the boat shop I bought it from and his first thought was dirty fuel. I cleaned the carby but stuffed up the float so ended up taking it into the boat shop. Turns out the carby "needed" replacing and he put a 2nd hand carby on it. But the same problem is still there.
The boat shop in now talking electrical.
Has anybody else experienced this type of problem?

Cheers
David

[Roughasguts]

Hmmmm never replaced a carby on anything cause it was stuffed.
Unless the carby caught fire or was under the ground for a year or two I can't imagine it being totally stuffed. Sure it could easily need a kit through it but that's all.

Sounds like it's in some form of limp mode, motor gets hot engine management device only lets the motor idle until cooled down.

On the other hand that doesn't make sence! cause the motor will get hotter at idle than say 2000 Rpm.
You done the finger test thing hold your finger if you can on the head near the spark plugs and count up until your finger is uncomfortable.

If you can count to 7 seconds it's not over heating, by the way you do have to use a differant finger if you try another spot on the head. The lower on the head you test the colder it will be, but as you get higher the head gets hotter, as heat rises.

I would suspect possibly a coil is shot and as it gets hot it stops working then gets colder and starts working again.

So see if you can borrow a coil pak from somewhere and test it out! being a johnson I would say the coil is stuffed, There fairly prone to it.

[Spaniard_King]

David,

if the engine is as you have stated "an early 90's model"..sorry to say but that model was a dud.. due to the UFI unit. It was a model where OMC was toying with a new ignition unit "Under Flywheel Ignition".. which basically means they moved the CDI "black box" from the left rear of the engine to the underside of the flywheel. They decided a few years on .. after many UFI failuresof the black box to go back to where they were..

Have your dealer take the flywheel off and see if the flywheel is contacting the UFI unit causing some damage... not sure on the availability of the UFI's.. you may have to convert it back to a standard CDI model..if so a wrecker will do it at a better price than a dealer.

[smithdt]

Roughasguts and Garry.
Thanks for the reply you blokes.
I think I got "touched" with the carby thing -there was something stuck inside the inner tube that runs from the float bowl up into the Venturi (High speed nozzle ?). I noticed it when I cleaned it but it would have been there when I bought the motor. Anyway ...once bitten......
I haven't tried the finger test as yet, but I've got a good contact temp probe that I'll use on the next test run.
I'll have a look at the coil as well, and the CDI if needed.

Thanks again for the tips guys.

Cheers
David

[Rockrash]

Hey David, Unplug the over temp sender from the back of the power head. The thing will run fine without it. It will of course melt if you actually do catch a bag or similar. I purchased a 25 Evinrude brand new in 1995 and it started doing what you are describing almost immediately. Took it back to the selling dealer without luck. I managed to find a guy who was an Evinrude guru who had all but retired. I told him the problem. He pulled the cowl, disconnected the sender and sent me on my way. The engine never did it again. I probably should have replaced the sender but I never got around to it. See how it goes.

[smithdt]

RockRash

Cheers for the info. That will be easier than getting the coils checked. Process of elimination..

Would the early 90's models have a "limp mode" though?

Regards
David

[CreelReaper]

Hey guys,
David, when the engine cuts back to an idle, is the fuel filter full. I had a similar problem on an old merc and it turned out to be the diaphragm in the fuel pump. It wasn't allowing full pressure in the fuel and letting too much air in. Just a thought.

Shane

[Rareone]

Goodday. If you go back to last months threads on boating where I added a thread asking for some advice on the same problems as you are having. You will see that I had the same problems that you have. I have a Tohatsu 50hp 2 stroke that starts well went for about 7 to 10 minutes at cruising speed about 4800rpm then dropped down to around half revs and would not rev out. Leave it sit for about 15 mins and it would do the same again on start up, but run at 2500rpm it went ok.
I had the experts have a look at it and they were stumped. I thought I could have been fuel problems as t he symptons were like it was having trouble sucking the fuel through or the vent was closed. Thought it might have been electrical in the black box. Tried all the warnings but they worked ok. Cleaned out the oil and fuel filters and replaced the oil in the resivore.
BLOODY BINGO<<<<< Problem solved. The oil was the problem. Since I have changed the oil I HAVE HAD NO PROBLEMS. The motor is back to its old self. Runs great.
Hope this helps.

[Rareone]

Oh. I might add, that the motor has a warning light and buzzer for the overheat and a buzzer for the out of oil warning. When the problem was on, the buzzer and light didn't come on, the motor was not hot and the pumpper for the fuel was hard. I checked that the warning devices were working by shorting them out. No problems there so eventually thought what I had done just before the problem began. Remembered then about the oil I put in last. Hope u find the problem, let me know what happens.

[cormorant]

Had you changed oil brands or types?

[Rockrash]

To the best of my knowledge the engine in question has no warning light or buzzer. The engine drops to pre determined rpm in the event of a drama. This was the case with my '95 model anyway-definately no lights and buzzers. From memory once there is a problem the ignition sends a scatter miss thru the engine thereby reducing rpm to safe levels. To clear things up in my case the ignition system was operating fine, it was the sender that was faulty. Shorting the system will not eliminate a sender failure. In reality shorting the system sends a false signal to the ignition system, which the ignition system then acts upon. A faulty sender does the same thing- sends a false signal to the ignition.
It may well be something else. As somebody else has stated, start with the easy and cheap and progress from there

[Chimo]

Hi David

Sorry for the late response as you may have sorted it by now. Anyhoo I''ll put in my two bobs worth re the fuel side of things. I had the same thing happen twice within ten hours of each other ie run well up to what ever revs then cut out or only run slow. Turn off for a few minutes and then same again over and over.

It was the fuel pump and the issue was that one of the springs on either side of the fuel pump diaphram had let go so the pump could only move small volumes of fuel.

Same thing twice as I said, with in ten hours on both OMC motors.

May not apply to you but its something else to consider esp on an older motor.
Also IMHO you need to find an older OMC Master technician to help sort the problem out as even for them it can take a while but they do sort it and they have better access to the bits you may need. Where are you by the way?

Good luck with it.

Cheers
Chimo

[tunaticer]

My 95 evinrude 25 had a hiccup like that once in the wee hours heading out fishing. Ended up i noticed i had not pushed the choke pump fully back in and it flooded the motor as soon as i backed off from near WOT. Took a while to get it to start again.

Two other things to check, the fuel line connections, johnson and evinrude line connections sometimes suck air instead of fuel. I have removed the connector where you normally plug into the motor and put the fuel line permanently attached to the fuel pump so i only have the connector on the tank to keep an eye on.

Check that the coil is bolted firmly in place, if its not fully tight to the motor it can give bad electical supply to the firing.

My guess would be a dying coil, I had a 6hp Evinrude in a 70's vintage that would run on for three mins than shut down to idle for a minute then cut out completely. 1/4 hour later it would fire and run again. Replaced the coil and no more troubles.

Jack.

[smithdt]

Jack

No. I go this motor 2nd hand from a local boat shop. They fitted it about 2 years ago and I've done probably less than 10 hours. I haven't touched a thing on it. Except to clean the carby after this problem first started.

[smithdt]

Hey guys,
David, when the engine cuts back to an idle, is the fuel filter full. I had a similar problem on an old merc and it turned out to be the diaphragm in the fuel pump. It wasn't allowing full pressure in the fuel and letting too much air in. Just a thought.

Shane

HI Shane.
The bulb in the fuel line from the tank was hard, but It doesn't have a fuel filter that I can see, so I'm not sure.
My biggest problem is I don't know enough about these things and I don't even have a manual. I'm posting a new thread to see you may have one I can copy.

Cheers