Interesting discovery-mercury 115

[pinboy122]

Hey everyone,I recently bought a 95 mirrocraft aluminum fishing boat with a 115 merc.The 1st time I put it on the water I was disappointed in the power.Trimmed out with just me in the boat I could only get about 33 mph and about 4500rpm.It usually started a little hard but sounded ok,got out of the hole ok and in general ran ok.So I changed the plugs and the top cylinder(4 cylinder engine)was fouled out,now IM thinking I need to rebuild the carbs which looks like a pain inthe *****.I decided to do a seafoam de-carb 1st so as I was doing that I noticed that the linkage was not attached to the top carb.I finished the de-carb,put the boat in the water and WOW what a difference!!!Out of the hole like a beast,46mph with 3 people and the rpms were right at about 5200.Now my question....What kind of damage could have been done with that top cylinder just getting "dragged"around?Im not sure how long its been that way.I guess it could have been a long time,or maybe just since the last time he had it serviced there's no real way to know.I checked the compression before I bought it and they were all a little over 140.Any thoughts???

 

[woody66912]

Re: Interesting discovery-mercury 115

The only damage you did is now you will burn more fuel.

 

[CRJDriver]

Re: Interesting discovery-mercury 115

Those cylinders may not have been receiving enough lubrication. The fuel is the lubrication! Should be ok if it was not run for a long time like that.

My opinion...I am not a mechanic.

 

[pinboy122]

Re: Interesting discovery-mercury 115

Yeah,im good with the more fuel thing lol!!! As far as the lubrication thing thats what I was kinda worried about.Each cylinder has its own carb so only one was effected but that 1 cylinder was getting pulled along at 4000+rpms with only an idle amount of fuel/oil.I think Ill recheck the compression and see where its at.

 

[CRJDriver]

Re: Interesting discovery-mercury 115

A compression test is ok....but a leak down test is far better. Uses an air compressor and a gauge to measure how much air is escaping the cylinder.
In my tower of power the number 3 piston was making great compression as it was distroying it's self.

 

[pinboy122]

Re: Interesting discovery-mercury 115

Ok,just checked the compression and its from top(cylinder that was disconnected)to bottom. 132--135--132--138.IM not sure what its supposed to be but it seem pretty good to me for a 1995.I dont have the means for a leak down test but have always wanted to try.I have a compressor,is the gauge something I have to buy or can I make my own?

 

[TLB2]

Re: Interesting discovery-mercury 115

Your engine is most likely OK . A leakdown tester is a specialty tool, It could be made if you could find just the gauge.

 

[CRJDriver]

Re: Interesting discovery-mercury 115

I agree. You were getting some lubrication. It wasn't like it was running dry. You can buy a leak down tester, maybe rent one at a tool rental center, or borrow one. They are used at all shops that repair piston powered airplanes and most marines that work on outboards.