over heat now hve low comp on one cyl. evin 150 1981

Benny1963

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Sep 17, 2006
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two year old power head low use. changed thermos and water pump.
took boat out fishing marsh sucked up some mud
burnt up new impellar, and one poppett on right bank
compression before this was 115/110 115. left bank .
40 110 115 on the right bank
the hole with the 40 reading is below thermo cover that melted poppett
was wondering if it could be blon head gasket , or have i damaged
that one cyl,and were to go from here .
thanks benny 1963
 

mikesea

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Re: over heat now hve low comp on one cyl. evin 150 1981

The head gasket is a likely candidate,but not guaranteed.Start by taking the head off,get yourself a nice flat surface ,using a piece of 80 grit wet n dry sandpaper run your head over the paper a few times,be sure it remains flat,then look at the sealing surface and note if there are any areas that are not getting sanded,that will show where your leak can bee,you can use this process to get it right,dont need to be absolutly hitting all areas ,but is best,though,you dont want to take too much material off.Just give it a good clean surface,clean the block side as well,you wont have a warp problem there,change all your melted parts,torque evenly,240 INCH pounds MAX.NOT FOOT POUNDS.Go up in even increments,starting from inside and working outward in a circular pattern.On an older motor,I am always afraid of the 240,though that is what the book says,you might go 220,if anything starts to feel like it wants to strip,stop,if its 200 or better,go with that,the bolts that are prone to strip are the bolts close to the ehhust cover,or the inside,there is very little meat there and the inserts can give,just a cautionary bit of advice from a guy that had to re insert many.You might change the other side as well.Good luck
 

Benny1963

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Re: over heat now hve low comp on one cyl. evin 150 1981

do you think its possible that it is head related the power head is new er had good comp on all other cyls
and had good comp on that cyl pryor to over heat
can a head gasket cuse one cyl to drop that low on comp.
also when i pull head waht should i look for play in piston cyl damage/ hole in piston
thanks bennyb
 

Silvertip

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Re: over heat now hve low comp on one cyl. evin 150 1981

The job of the head gasket is to keep compression inside the cylinder. If the gasket is leaking, compression is allowed to escape so yes -- that can cause low compression on one or more cylinders. Since you packed the engine with mud, it has very likely now hardened so you have a job getting it out. Drop the lower unit, remove the heads, poppet, thermostats and using water up the lower unit pipe, try and flush things out. Water should come out the thermostat and poppet openings. Then flush it backwards. Kleen the tell tale tube with weed whacker line. Install a new water pump. While you have the heads off, look for scoring on the cylinder walls. If you find some, chances are the piston is also scuffed and from here, don't bother to put it back together. It's rebuild time. If you dress the cylinder head gasket surface, place the sandpaper on smooth surface, like a sheet of glass and work on that to ensure you get a flat surface and can detect warping. Using sandpaper on your hand doesn't work.
 

Benny1963

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Re: over heat now hve low comp on one cyl. evin 150 1981

took heads off it has 6 clean 030 pistons in it .the head gasket was blown at steel ring on the bad cyl im going to surface head like you said and replace
gaskets do the head gaskets need sealer or do they go on without
all cyls are clean but slightly glazed there seems to be a little movemant
on all the pistons side to side . i build car motors and they are usually tight
in the bore any input app.
bennyb
 

tashasdaddy

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Re: over heat now hve low comp on one cyl. evin 150 1981

sounds like you dodged the big bullet.
 

Benny1963

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Re: over heat now hve low comp on one cyl. evin 150 1981

yes it seems i dodged the big bullet but with my luck it will hit me somewheres
else,fr said to change exhaust gaskets my manual is lacking in this dept.
any help in that area would be app.
thanks benny
 

tashasdaddy

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Re: over heat now hve low comp on one cyl. evin 150 1981

yo can see complete diagrams at "http://www.evinrude.com/en-US/Accessories/Literature/?popup=true"
 
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