1997 johnson 150

[Jeff ashburn]

Having issues with my outboard. Bogs down when taking off. Once on pad it only runs abt 4000 rpms. The prop has lots of soot around the inside. Checked compression on all cylinders 60 to 70 psi on all cylinders.  Was told it could be electrical problem. Any help any advise would be appreciated. 

[fishnkamp]

Give us some info first. What boat is it on? How well has it driven in the past?  What rpm did it get when it ran well?  Do you have a fuel filter in the system? Have you tried to replace it. Have you replaced spark plug wires, spark plugs? Have you checked your lower end oil? I would dump it and check it for metal and water, sometimes a lower end problem looks like an engine issue. Do you have to run ethanol fuel? If so I would obtain some fuel hose,a small marine gas tank, fill fresh fuel and hook the new fuel line directly to the engine. Just temporarily set it on the floor of the boat and go for a test run. If it work okay chances are you will need to pump out all of the junk fuel and replace it with fresh. Next replace the entire fuel lines from tank to engine. Ethanol is tearing up fuel systems. And even if you do not use ethanol fuel you may have gotten some trash fuel from somewhere.   Another thing to consider doing is running a can of Sea Foam in that small tank. You could have dirty carbs because I think that is a carbed motor. I have very little Johnson experience but if they have a diaphragm fuel lift pump it could also need to be replaced.  Most of my experience over 40 years has been with Mercs sorry.  Give us some answers and we will try and get a little more specific.  I would start by replacing the maintenance items I mentioned. Sometimes we forget to do the simple things, I hate wasting money but to replace old spark plugs, wires, fuel filters, lower end oil etc is hardly a waste.  It is improvements in the engines running condition and a simple way to check the items off of the troubleshooting tree. Good luck. Let us know how it progresses.  It still could be more involved but I would check off the easy stuff first.

[Way2slow]

First, I wouldn't do anything else until you check is your compression gauge, because if it's accurate, you need to start by replacing/rebuilding the power head, don't waste time or money throwing other stuff at it until it has a whole lot more compression than that.   If that is the true compression, I would think it would be hard to start also, but definitely would be way down on power.

Also, on a two stroke, make sure the carburetor butterflies are open when doing a compression test.  It can't make compression if it can't get air.

A good fresh engine, will give you 125psi across the board, with an accurate gauge.

[fishnkamp]

way2slow is right I kinda did not pay attention to the compression readings.  The fact that they were so even i goofed and was not thinking about the fact they should be higher. You need to find out what the specs are first and if you were getting correct readings

[crypt]

have same engine ,normal comp. should be about 115-125 anything below 100 it's worn out

[Indianabasser]

Try do a decarb first. Brp engine tuner or seafoam deepcreep are what you will need. Get the motor up to normal operating temp on muffs then spray down each carb throat until it almost dies. Then take out each plug and spray inside the cylinders. Replace plugs and let sit for 24 hours. Take to lake and run it good. While your on the water push the choke/enricher, if the engine picks up its a fuel issue. If it bogs down even more it's an electrical issue. Re check your compression again and see if it helps. If numbers go up you will need to replace the plugs. It's cheap and easy instead of starting to throw money at it. It's recommenced to decarb every 100 hours.