1996 48hp Johnson

Johnny Moore

Cadet
Joined
Sep 7, 2016
Messages
6
My motor is idling rough and when I put it in gear to run wot it just bogs down. It will not run at full rpms. I checked the fire. Both coils r good. Both plugs r good. Replaced fuel line. There is unburnt oil and fuel coming out of exhaust ports by lower unit. Can anyone tell me the problem r what else I should look at r change? Thanks guys
 

flyingscott

Fleet Admiral
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Apr 8, 2014
Messages
7,985
Then compression. If that is good look at the carbs could be a float or needle issue.
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
36,033
Possible that the fuel pump diaphragm is ruptured.---A " no money spent " check to do.
 

Johnny Moore

Cadet
Joined
Sep 7, 2016
Messages
6
That's what I was thinking because it will turn the rpms when I put it in reverse. When I put it in forward it just bogs. Then sometimes it acts like its gonna take off. I just had the carbs cleaned out at dealership.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,033
??---In reverse there is lots of exhaust around prop and therefor less load on the prop.---It will rev up easier !---Test compression.---Perhaps inspect for a sheared flywheel key.
 

oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,598
^^what they said.

Measure spark with an adjustable tester, if you haven't done it that way. Additionally, shops use their own fuel for control purposes. If you go back to bad fuel with clean carbs, problems return. Check your fuel. Water will be at the bottom, down at the intake, and will slosh around some. (Adding a layer of fresh fuel won't solve the problem.)
 

Johnny Moore

Cadet
Joined
Sep 7, 2016
Messages
6
I went back with clean fuel with some ethanol treatment in it. Has good compression on both cylinders. Plugs were soaked with fuel. Not dry r bronzed color. Plugs r not filed though.
 

juno pierrat

Petty Officer 1st Class
Joined
Dec 14, 2013
Messages
355
I have a 87' 48spl, twice now had these problems, ran normally to start day then ruff idle and bogging and a very ruff running 1800 rpm max ,it was a bad charge coil, 48's are great to work on, and cheaper, under fly three separate parts stator, trigger sensor and charge coil,(most models everything is combined and $$ to replace) electrical testing takes a manual and special volt meter, but if you what a quick visual check, remove flywheel and see if there is a dark goo draining from electrical parts, sure sign its bad.
 

Johnny Moore

Cadet
Joined
Sep 7, 2016
Messages
6
Wow that sounds crazy. Let me ask y'all this. Is this fuel pump operated by a vacuum from the block? There is a third fuel line going to the block which I figured was used for vacuum to operate fuel pump.
 

jakedaawg

Rear Admiral
Joined
Jun 26, 2012
Messages
4,275
Yes, attached to a pulse fitting if you have a 3 port pump.

You need to start with an open air gap spark check. And a compression test. Report back the results.

How to do these tests is located in the sticky at the top of the Forum.

With answers to those two simple test someone can point you in the right direction.
 
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