86 175 johnson...HELP

[bgooden]

got a 175 Johnson and my problem is when it runs for a little bit (like i'm flushing it) it starts running rough at an idle. i didn't check the plugs yet to see if they are fouled but i was conserend that i seen some gas and oil in the pan under the motor, i don't know what it's really called...ha ha but i didn't see where it was coming from. does it sound like it is running rich? how do i adjust if i am? please help me i'd like to take my boat out and not break down.

 

[emdsapmgr]

Re: 86 175 johnson...HELP

I'd check for spark on all 6 cyls. first. A spark checker or inductive timing light should be used. The carbs have fixed jets thoughout, so they are preset by the factory and not adjustable. You can set the idle speed. It should be set to 650-750 rpm when idling in gear, floating in the water. You can remove the airbox cover to inspect the front of the carbs to see if they are leaking any oil/fuel. Esp. when the engine is tilted for trailering. You could have a bad airbox cover gasket.

 

[bgooden]

Re: 86 175 johnson...HELP

I pulled the plugs and the top one on each side had alot of oil on them. Is this bad? or would it just be the cycle of the motor where these were going to fire when i turned the motor off? It only runs rough at idle when i give it a little gas it runs smooth. I think you might be right about the air box cover gasket i need to check it tonight.Is it kinda like a vacum leak in a car?

 

[jonesg]

Re: 86 175 johnson...HELP

How old are the sparkplugs, has the engine been decarbed recently, just wondering what the service history is. A seafoam treatment can work wonders. Is the compression good ?

 

[bgooden]

Re: 86 175 johnson...HELP

the plugs look new ,they were in it when i got the boat. the compression is fine. about 100 per cylinder.

 

[emdsapmgr]

Re: 86 175 johnson...HELP

So the top plugs looked different from the other 4? If so, you may have something going on in the carbs. When at idle, the carb butterflys are (should be) completely closed. Fuel is fed to the engine through idle passages that are only used when the throttle plates are closed. If these get clogged with dried fuel, it won't idle right. As soon as you open the throttle plates, even slightly, the carb draws fuel from the other jets in the carb, which is probably why the idle smooths out. You may want to pull the carbs apart and clean all the carb body passages with an aerosol carb cleaner. Be sure to pull all the jets out and inspect them. When you reassemble, double check the sync and link setup. Your compression sounds fine.

 

[bgooden]

Re: 86 175 johnson...HELP

I went to replace the air box gasket and found out that there was no gasket there! i replased it and it runs better for now. Now i need to replace the water pump. How hard is this to do or do i need to take it to a mecanic? I do have mecanical experiance to a point , i have never worked on a boat motor before. Do i need special tools? I plan on replacing all the seals that i can while i have it apart.

 

[emdsapmgr]

Re: 86 175 johnson...HELP

Replacing the water pump impeller is a fairly easy job, if you have the factory manual that has the illustrations. When you say you want to replace the seals, do you mean the seals/oirings in the pump, or do you want to reseal the lower unit itself.? A reseal on the lower unit definitely requires the factory manual and some mechanical expertise.