Engine misfire

I know I have touched on this before, but running up the outboard today and previously, once the motor in forward (or reverse) goes past 2500rpm, it seems to misfire dramatically and brings it back to 2500rpm. The motor is a Johnson 150hp 1993 2 stroke.

My question is: Is this Johnsons way of limiting revs when the motor is not under load, or could it be something more to do with maintenance? I know there is a S L O W system to reduce engine revs when the engine gets too hot but this is when it has only been running for a few minutes and the tell tale and the block are still only warm. I have checked all the wiring and replaced some connections which were suspect but this has made know difference. It has fresh fuel, the plugs are new and set at .030" and the it does not overoil now.

Any thoughts?

It will be going into All Boats soon as that is where I bought it secondhand, and they have kindly offered to check it out under the so called warranty, but I am not a person to let an engine beat me!!!!

This is the engine.

____________________________________________________________________________

Wherever you go, there you are

Image Upload: 

Feral's picture

Posts: 1508

Date Joined: 01/11/06

Maybe you checked it already

Thu, 2011-10-27 18:13

Maybe you checked it already .. but drop the fuel in the the carby bowl .. my next suggestions is to siphon the very bottom of the tank .. sounds to me there is water down there .. jmo

davidbland50's picture

Posts: 392

Date Joined: 24/07/11

What, all six carbies?!! The

Thu, 2011-10-27 18:16

What, all six carbies?!! The fuel may be a concern but it was only new a couple of weeks ago.

____________________________________________________________________________

Wherever you go, there you are

Posts: 4577

Date Joined: 01/02/10

I would lean more towards a

Thu, 2011-10-27 18:31

I would lean more towards a coil breakdown. Sounds electrical to me.

____________________________________________________________________________

Does anyone know where the love of god goes, when the waves turn the minutes to hours?

Posts: 539

Date Joined: 29/03/10

Agree Dodgy, I have trouble

Thu, 2011-10-27 18:35

Agree Dodgy, I have trouble once with my old 50 2 stroke, would start to misfire as the RPM rasied. Acted a bit like a rev limited, took the punt and put new CDI's(coils) and presto problems gone.

 

CCC

davidbland50's picture

Posts: 392

Date Joined: 24/07/11

Now we are talking about the

Thu, 2011-10-27 19:21

Now we are talking about the CDIs here not the power pack. quite a difference in price between the two. Where should I go for them? Somewhere, here in Perth?

____________________________________________________________________________

Wherever you go, there you are

Posts: 539

Date Joined: 29/03/10

not sure on the terminology

Thu, 2011-10-27 21:33

not sure on the terminology but the black bit(coil like) with the spark plug lead attached

 

CCC

wangler's picture

Posts: 607

Date Joined: 26/04/08

somewhere in here ?

Thu, 2011-10-27 20:05

 http://www.boats.net/parts/search/BRP/JOHNSON/1993/J150NXATG/IGNITION%20SYSTEM/parts.html

____________________________________________________________________________

Want to make someone mad... tell a lie! Want to get the world upset... tell the TRUTH !

Dougie

strike_zone's picture

Posts: 403

Date Joined: 09/09/10

evinrude dealer

Thu, 2011-10-27 20:06

go to a evinrude dealer muhlings or hayway marine ect

 

davidbland50's picture

Posts: 392

Date Joined: 24/07/11

How many CDIs are there in

Thu, 2011-10-27 20:39

How many CDIs are there in the V6? Its dark outside at the moment.

____________________________________________________________________________

Wherever you go, there you are

Posts: 2925

Date Joined: 27/12/06

Boat city

Thu, 2011-10-27 21:37

Boat city balcatta know these engines well

just dhu it's picture

Posts: 1081

Date Joined: 14/05/09

fuel pump

Thu, 2011-10-27 22:13

check that your fuel pump can supply the motor with enough fuel at the set revs , other wise the dealers your best bet

dan1's picture

Posts: 379

Date Joined: 11/07/07

cant be much fuel or spark

Fri, 2011-10-28 13:32

cant be much fuel or spark its a two stroke ????????

davidbland50's picture

Posts: 392

Date Joined: 24/07/11

Trial run

Fri, 2011-10-28 20:36

I found out I have three coil packs. I am going to wait until the boat is completed, take her out and give it a good run. I have a feeling it may be a type of speed limiter to stop you putting a piston through the block because it isn't under load. We shall see.

____________________________________________________________________________

Wherever you go, there you are

Posts: 812

Date Joined: 09/10/06

Was the motor running good

Sat, 2011-10-29 10:36

Was the motor running good when you bought it?

l dont think a 1993 Johnno had a saftey rev limiter. You would be getting an audible alarm first. l could be wrong though.

l would be taking it back to place of purchase before the warrenty runs out. 

davidbland50's picture

Posts: 392

Date Joined: 24/07/11

As is

Sat, 2011-10-29 11:20

I bought the motor second hand from All Boat. It had come off a larger boat as one of a pair. It was purchased with a condition report. It all seemed to be good condition. The audible alarm has gone off a few times that I have been running it.

____________________________________________________________________________

Wherever you go, there you are