Can the seasoned boaters help me out with compression and running properly

[bfan781]

Hey guys,
I have a 98 115hp mariner outboard. Boat just isn't running correctly. You can just tell by the way it sounds. Rough idle. stalls occassionally. It does everything its supposed to but something isn't right. So far we have checked for spark. changed plugs, checked and adjusted timing. compression on all four cylinders is between 93-100. THat seems low, but if they are all like that that mean something else? Can't seem to imagine them all wearing equally. What else could it be? what are some easy tests. I also rebuilt carbs last summer. It starts idles and will operate correctly but just not acting as it should. Please advise and help out you could/ thanks.

 

[JB]

Re: Can the seasoned boaters help me out with compression and running properly

Whatever your trouble is, it is not compression.

 

[aussieflash]

Re: Can the seasoned boaters help me out with compression and running properly

So you changed all needle n seats?Checked float for saturation and adjusted float levels.Changed ALL gaskets in carbs?Check all lines for cracks etc.If it splutters and coughs back through carbs at idle you might want to check reeds and valves.

 

[Jake.]

Re: Can the seasoned boaters help me out with compression and running properly

+1 to looking into the carbs

 

[bfan781]

Re: Can the seasoned boaters help me out with compression and running properly

OK so I took some advice and pulled the carbs again. Everything looked good as far as seats needles and floats. Now let me remind you that the boat ran good last season and when I took it out this season is when the issues arose. I noticed when I pulled the carbs that the gas in the bowls was very blue. COuld that be from the fogging during the winterizing? When I cleaned them before it was just gas. COuld that cause the boat to run bad? I have since cleaned them good but have not installed and retired it.

 

[j_martin]

Re: Can the seasoned boaters help me out with compression and running properly

There should be enough oil in the gas by the time it reaches the carbs that you can see it. If it's thick and oily, them something's wrong. There's no way fogging oil can get in there.

I don't know the oil injection system on that engine, but it might be some of the problem.

edit.... Just looked at a parts diagram. Unless it's obviously over-oiling, I don't see a likely failure there.

The other thing that makes engines sputter at idle, load up, and then seem out of sorts is the bleed lines and bleed check valves.

 

[bfan781]

Re: Can the seasoned boaters help me out with compression and running properly

What about if the oil was sprayed into the carb throttle body? Then it could get in there right? This wasn't thick like the oil the engine uses it was like blue gas. If it was in the fule bowl would it run lousy?

 

[aussieflash]

Re: Can the seasoned boaters help me out with compression and running properly

Blue fuel in your carbs.Sounds like your getting 2 stroke oil intrusion in your fuel.Oh hang on,that's good....Check your reeds/valves.....for the 3rd time.

 

[bfan781]

Re: Can the seasoned boaters help me out with compression and running properly

Whats involved in checking reeds/valves? Only reason I mention the blue is because last time I cleaned carbs it wasn't blue like now.

 

[j_martin]

Re: Can the seasoned boaters help me out with compression and running properly

How in heck would anything in any quantity get from the carb throat to the float chamber? NO, what you sprayed in didn't get into the float chamber.

The fuel there should be blue, but not thick and oily. If it was totally colorless, that was a problem.

If it idles without spitting at you, the reeds are not the problem.

heck, I give up.

 

[bfan781]

Re: Can the seasoned boaters help me out with compression and running properly

ok guys. go easy. Just learning all this. Lot to go through. The gas was not thick so it probably wasn't the issue. Just don't recall it last time. At the bare minimum, I gave the carbs a good cleaning going to install them again tomorrow maybe it was another carb related issue.

 

[bfan781]

Re: Can the seasoned boaters help me out with compression and running properly

Could I ask where the bleed lines and bleed check valves are and what is involved in checking and cleaning them?

 

[aussieflash]

Re: Can the seasoned boaters help me out with compression and running properly

Your bleed lines are the thin lines running from cylinders to just behind carbs.Different set ups for different engines.You need to get a Merc manual for details.Good luck.