1977 evinrude 140hp no comp 1 cylinder

[feral]

hi,<br /> firstly thanks for all the help i got last time.<br /><br />number 4 cylinder has zero compression(or not enough to register on the tester) the other three are 100 110 100. the engine still runs fine (with a miss). could this be a major problem or something simple like a reed valve? assuming outboards have reed valves like a 2-stroke motorbike. or is it more likely to be a piston( would of thought there would be a small amount of compression). any help would be greatly appreciated as i don't want to do an unneccesary rebuild.<br />cheers

 

[reeldutch]

Re: 1977 evinrude 140hp no comp 1 cylinder

if you have 0 reading i would advise to pull the head off and see whats going on.<br /><br />i dont think its the reedvalves.<br /><br />it sound like broken rings or if you are lucky a blown headgasket.<br /><br />to replace the headgasket will cost about 20 dollars to do a rebuild about 1500.<br />so pull the head annyway.<br /><br />good luck and keep posting there are a lot of people here who are very knoledgeble.<br />i'm just a do it yourself wrencher but there are some real pros around here.

 

[rodbolt]

Re: 1977 evinrude 140hp no comp 1 cylinder

time to remove the head. its toast. never seen a blown head gasket with a zero reading. but maybe your lucky.

 

[feral]

Re: 1977 evinrude 140hp no comp 1 cylinder

thankyou, i will pull the head over the weekend and i will keep ya updated.

 

[piniongear]

Re: 1977 evinrude 140hp no comp 1 cylinder

I would expect to find that piston burned thru at the top edge because these model (pistons) had the ring gap to close to the top of the piston. This was a known design error and the pistons were later changed (about 1980) although the factory continued to install the old pistons until about 1983-84. No doubt to use up the inventory on hand.

 

[feral]

Re: 1977 evinrude 140hp no comp 1 cylinder

I took the boat out yesterday and after it gets on the plane ( with a great deal of effort) it goes like it's running on all four,very very powerful.however, i think that if the seas kick up i would not be able to reach plane , so, is it possible to replace the one piston without pulling down the entire powerhead? i ask this as i am on a very tight budget and would prefer to buy a gasket set rather than a rebuild kit as a rebuild kit is about $1000 US which i think is about $1500 AU and thats a months pay.if not are there better brands or are they all fairly similar.<br /><br />again, i can't express how grateful i am to you people.

 

[rodbolt]

Re: 1977 evinrude 140hp no comp 1 cylinder

pull it apart and inspect whats left. then we can assist with a parts list.

 

[reeldutch]

Re: 1977 evinrude 140hp no comp 1 cylinder

if i was you i wouldnt take the boat out untill i know whats going on.<br />you might cause more damage next trip or trash the whole block.<br /><br />no you cant replace only one piston without disamling the whole block.<br />but you might be running to fast.<br />pull the cylinderhead and let us know what you find.<br /><br />good luck reeldutch