Evinrude 150 (low compression on 1 cylinder)

[emdsapmgr]

Re: Evinrude 150 (low compression on 1 cylinder)

If you put oil in a cylinder, then take a compression reading-you will get false readings, higher than normal. Best to just let the suction of the carbs provide fuel/oil lubrication to the cyls. You could well have no spark on the bottom two cyls. The bottom carb could be all gunked up to the extent that it will not flow any fuel/lube to the bottom cyls-that might explain a low compression reading on one of the cyls. Or you could have an internal water leak that typically affects the lower cyls. Before you put any more money in it, I'd make sure the powerhead is not trashed. Pull the head with the low compression cylinder side and see what is going on. You may need to pull the side intake cover on that cyl to get a look at the side of the piston.

 

[Dudemaaan]

Re: Evinrude 150 (low compression on 1 cylinder)

The boat has no gas/oil in it right now. I knew the oil in the chamber would likely skew the readings, but In my mind I figured it would tell me if the rings were sticking/worn. If it was the head gasket I didn't figure the oil would have any effect, but maybe I'm wrong. I was also trying to decide if a cylinder wasn't combusting if that could somehow lower the compression readings. I just can't think of how. Feels like there are some clues here, just not sure how to read them. At any rate sorting out the ignition is the next step.

 

[mikesea]

Re: Evinrude 150 (low compression on 1 cylinder)

clean plugs on the bottom 2 cylinders makes me believe you have a no fuel delivery on the bottom carb,it feeds both cylinders,if water was entering ,you would likely have a rust indication on the plug,.AT this point ,pull the headlook for gouging on the cyl walls,its possible that the other non firing cyl hasnt been hurt yet,to have a low reading in that cyl,indicates more damage then just a carbon build up,you can do the de-carb,but its wishful thinking,but anything is possible,I would hate to see something let go and cause more damage,a set of gaskets(or 10is a small price to pay when u got the rig for free,

 

[Dudemaaan]

Re: Evinrude 150 (low compression on 1 cylinder)

Thanks for the suggestions. There is definitely no rust on the plugs. I'll take some pics of them in a bit and post them up. I would think there would be evidence of a lean condition, unless the carb is just completely stopped up... I'll take a look at the bottom carb and see if the jets look plugged. Or maybe I'll first put some gas in the tank and see if any fuel gets to the cylinders.

 

[Dudemaaan]

Re: Evinrude 150 (low compression on 1 cylinder)

Pics of the plugs, and a shot of the boat. As you can see the 2 clean plugs compared to the very black plug. 4 top plugs are black like that and then the 2 lowest plugs are super clean. Click to enlarge