85 150HP Johnson

[denton]

I am having a problem with my 1985 150 Johnson bogging down at high RPMs. I had an ignition problem which was recently fixed so I know that I am getting good spark on all cylinders. When I first take the boat out I can get up to about 4000 RPM and it starts to bog down. From that point forward, I can't get above 2500. Just found out tonight that if I press in the key to prime the engine while it is running, the RPMs pick back up to where they should be. The primer ball stays hard the whole time. I recently ran a can of cleaner through the carburetors. The motor was rebuilt last year. Any thoughts would be greatly appreciated.

 

[HighTrim]

Re: 85 150HP Johnson

Were the carbs rebuilt at the last time, the high speed jets may need cleaning, you will need a special tool to take them out, or you can make one out of a screw driver and belt sander. Have a look at the tutorial.

"http://www.meegsonline.com/tmd/TMDsVideoChronicle2.wmv"

 

[tashasdaddy]

Re: 85 150HP Johnson

totally agree

 

[denton]

Re: 85 150HP Johnson

The carbs were rebuilt last year, but I guess something could have gotten in there. Do you think all the carbs need to come out and be rebuilt again, or just remove the jets and clean them? It may be a dumb question, but I've never dealt with this before. Thanks!

 

[HighTrim]

Re: 85 150HP Johnson

Who cleaned the carbs? The high speed jets are often misssed since they can be stripped if not taken out properly, and are often bypassed in the cleaning stage. The tool is easy to make, TD has pics if you ask him with specs. Simply soaking them is not enough, you have to at least, bare minimum get some wire in them and blast an aerosol cleaner through them.

 

[iwombat]

Re: 85 150HP Johnson

It could also be an air leak in your lines, and bumping the key richens up the mix enough to compensate. It's fuel delivery related for sure.

 

[denton]

Re: 85 150HP Johnson

The mechanic that rebuilt the engine last year rebuilt the carbs. I can't be sure if the jets were cleaned, and I doubt he would remember for sure. I would rather not take it back to the mechanic right now (I've already sunk more money into it then it is worth with the rebuild and the ignition problem.) From the diagrams in the manual, the jets are accessible without removing the carbs. Is it worth trying to remove and clean them without doing the whole carb (since that was done last year)? I have the rebuild kits and I don't have a problem doing the rebuild myself, but I am a little worried about syncing everything up afterwards. Thanks for your help!

 

[CharlieB]

Re: 85 150HP Johnson

Follow the previous link on carb cleaning and making the screwdriver mod into the correct tool.

You do not have to mess with the carb linkage, simply remove the float bowl drain screw, remove the jet thru that hole, clean and reassemble.

 

[72SideWinderSS]

Re: 85 150HP Johnson

Is it worth trying to remove and clean them without doing the whole carb (since that was done last year)?

Yes but why not do it right ?

I have the rebuild kits and I don't have a problem doing the rebuild myself, but I am a little worried about syncing everything up afterwards.

You have the manual already and the kits, it's a piece of cake to do the link and sync.
It doesn't take very long to melt R down if one, or more, of your cylinders go to lean. BTDT

 

[emdsapmgr]

Re: 85 150HP Johnson

The primer bulb should pump up to a "firm" feeling when you get ready to start the engine the first time. After that, it will loose some of it's firmness, but should not collapse. If it gets really hard, one of the check valves in it could be bad. That can cause a fuel restriction and running problems. If the bulb is going bad, a simple thin like orienting the bulb arrow upward can help-or replace it. I'd check your fuel pump to make sure you are getting proper fuel volume at high rpm's. Your engine could be sucking more fuel from the carbs than the pump is replacing...

 

[denton]

Re: 85 150HP Johnson

Over the weekend, I rebuilt the carbs. You were all correct. There was crud in 2 of the three carbs and it was clogging the high speed jets. Got everything back together and motor is running great. Thanks for all of your help!

 

[Dhadley]

Re: 85 150HP Johnson

Someone was looking over you & your motor. When a cylinder on a carb'd OMC isn't getting fuel, it isn't getting oil either. Pistons don't like that. Go play the lottery, maybe you haven't used up all your good luck yet. Better yet, tell me the first 6 numbers that pop into your head.......

 

[commonarcwelder]

Re: 85 150HP Johnson

I would also like those 6 numbers.....If it would've been me it would have been one high speed jet plugged just enough where I wouldnt notice while running to my honey hole about 7 miles from the launch......The OMC God was with you my friend.......