Top speed with 18hp Evinrude on 14′ aluminum

[stephenspann27]

quote wannabe outboard guy:

One other thing to think about Stephen. Just because it makes compression when doing the compression test, whats not being measured is “blow by”. As was stated earlier in this thread, a leak down test will most likely reveal that it is not holding that cylinder pressure for the complete combustion stroke. That is where the significant power loss comes from. The pressure is leaking past the rings.

Point taken, I think I’ll buy a leakdown guage and do the test.

[wiscoboater]

re read my last post, as I have edited it.

[outbdnut2]

I had a cheapie compression gauge a few years back that had the check valve at the far end of the rubber hose (the cylinder end), so unless you were measuring a big cylinder, like in a big car engine, the volume of space in the hose between the checkvalve and the gauge offset the readings down significantly. Be sure you don’t have that problem. I tossed that one out.

[immulmen]

quote outbdnut2:

I had a cheapie compression gauge a few years back that had the check valve at the far end of the rubber hose (the cylinder end), so unless you were measuring a big cylinder, like in a big car engine, the volume of space in the hose between the checkvalve and the gauge offset the readings down significantly. Be sure you don’t have that problem. I tossed that one out.

My "Snap-on" gauge is like that,,,,I don’t think I am going to toss it!

[fisherman6]

My compression gauge has a hose about 12" long. I don’t find it errors to the low side if you continue to crank until the needle stops. For a rope start outboard I find it usually takes about 4 brisk pulls of the rope. I usually give 5 just for good measure.
-Ben

OldJohnnyRude on YouTube

[stephenspann27]

I picked up a leakdown tester today. I’ll get the boat out of storage tomorrow and do the leakdown and another compression test.

[stephenspann27]

Well, my neighbors house is on the market, and the realtor is having an open house today, so I’ll try to be less white trash and not park my jon boat in the driveway until this evening when the open house is over.

[billw]

You want to moon them while smoking a big stogie because if your neighbor’s house sells for too much, YOUR taxes will go up.

Long live American manufacturing!

[stephenspann27]

You guys were right. Both cylinders compression have dropped since I last checked it. I checked them with two different gauges, One gauge read top, 90 bottom 92, the other gauge said 80/82. The top spark plug was white, not chocolate, the bottom plug was chocolate. Most importantly the top cylinder (which is the one I took the pic of with the plate off) failed the leak down test miserably. The bottom cylinder shows "moderate" loss on the leak down. Looks like I’ve been running mostly on the bottom cylinder,.

[fisherman6]

That sounds pretty much like what was expected. It’s always good to know for sure and thank you for posting your findings. That powerhead needs a rebuild for sure. The unfortunate truth is that after checking that one out, you may end up looking for yet another replacement. Keep us posted on your progress. If you end up needing another replacement or even parts, probably best to post in the classifieds on here ratherthan chance another ebay purchase. Good news is there are lots of 18s around. Someone is bound to have what you need. It just sucks that you have put that much into it and you still don’t have a good engine. 😥
-Ben

OldJohnnyRude on YouTube

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