'79 115 knocking?!?!

[mikesjohnson]

115, came with boat (as in, threw it in the back of the truck on the way home from purchase) not running. it spins over freely, and has even compression, (131,131,127,129). when turning it over with the lower unit off for water pump replacement, i hear a knocking, and am not sure if it is normal. i have yet to try and run the engine, I was told it needed power packs. if i take off the block below the carbs, i guess it would be called a reed block, will that allow me acess to the connecting rods. I would like to have a look inside before i put any money into it. thnx.

 

[Walker]

Re: '79 115 knocking?!?!

if i take off the block below the carbs, i guess it would be called a reed block, will that allow me acess to the connecting rods. I would like to have a look inside before i put any money into it. thnx.

Nope, you have to split the crankcase to access the connecting rods.
Can you describe the knocking better. Those crossflows have a ticking noise, but I don't think you'd hear it unless the motor was running. Check your flywheel teeth and starter gear teeth.

 

[tashasdaddy]

Re: '79 115 knocking?!?!

how long has it been since it has been run. could be a very dry engine, just groaning.

 

[emdsapmgr]

Re: '79 115 knocking?!?!

Also possible you have some piston slap noise. Compression looks good.

 

[WillyBWright]

Re: '79 115 knocking?!?!

Pull the sparkplugs and put a pencil (eraser-end first) into each cylinder in turn, and rotate the flywheel until the piston is about midway in it's stroke. Up or down doesn't matter. Rock the flywheel back and forth and feel the pencil movement. If there is a noticable delay in one or more cylinders, that rod bearing may be bad. You won't get it in all cylinders, so if any one or two is obviously different than the rest, remove the head and watch the piston movement or see if any don't come all the way up to the top of the cylinder. It would come 1/16 to 1/8 inch short.

You probably wouldn't notice piston slap just turning the motor over, but you might with the motor running. That's not necessarily unusual. There's a lot of clearance between the piston skirts and cylinder walls on those.

 

[F_R]

Re: '79 115 knocking?!?!

I believe you can see the rods with the reeds off, but not service them. You can also see one side of the pistons by removing the 4 bypass covers off the sides. Going even farther, you can see the other side by removing the exhaust cover. Then there are the heads. By now you are approaching a complete powerhead teardown.

 

[mikesjohnson]

Re: '79 115 knocking?!?!

if i take off the block below the carbs, i guess it would be called a reed block, will that allow me acess to the connecting rods. I would like to have a look inside before i put any money into it. thnx.

Nope, you have to split the crankcase to access the connecting rods.
Can you describe the knocking better. Those crossflows have a ticking noise, but I don't think you'd hear it unless the motor was running. Check your flywheel teeth and starter gear teeth.

i have what i would consider a great deal of internal combustion engine knowledge. I have been an auto mechanic for 9+ years, specalizing in heavy line (engines/drivetrains) i have heard many knocking sounds from enings over the years, but have never dealt with roller bearing knocks.

its a wierd noise. when it reaches compression (spun either way, by hand, not the starter) it will only make the knocking sound turned into compression, not away. in other words, when rocking the crank back and forth, it only knocks in one direction. when i let the cylinder leak down it doesnt make the the noise when it would pull the excissive rod bearing clearance up, from the other side of the crank journal. that may not sound very clear, so let me further explain.

when you have a rod knock in a non-roller bearing crank, you get two distinct knocks. one when the pistion starts its travel from BDC to TDC, when the at the bottom of the stroke, and one when turning TDC to BDC, at the top of the stroke. this noise is at about mid travel, when about 1/2 way through compression. you say that these motors are noisey, i think i may just be hearing the noise they make. with such even comppression, I dont think i have a rod knock, or even piston slap, as this should show up in a compression test, to some degree.

i hope this helps. i would like to avoid tearing this thing down just to inspect the rods, but it does need a few dollars invested before i get it running, and I would hate to spend the money, just to find out that i need to do a crank and a rod also, as this would have made the investment of a refurb more than the enigne is worth.

 

[mikesea]

Re: '79 115 knocking?!?!

the fact that you only hear it one way,the sound you could be hearing may be the reeds closing.The best idea is the screwdriver ir dowel stick on top of the piston and feeling for loose rodbearing.yourengine is a crossflow ,so the rod ends are not exposed like in a looper,loopers allow the fuel to pass through the piston ,thus looping,whereby,a crossflow has the fuel run along side .No ports in the xflow pistons

 

[emdsapmgr]

Re: '79 115 knocking?!?!

Another remote possibility. Water in the fuel can damage the upper and lower crank bearings over time-esp if not winterized. Possible that these bearings could be bad. By the time these cause running problems, usually the upper crank bearing surface is also bad, requiring a new crank. The only way to detect this is a teardown.

 

[mikesjohnson]

Re: '79 115 knocking?!?!

well, i removed the heads and had a peak, and i found nothing. lots of carbon, no socring in the walls, all pistons come up to thier wearmarks, and non have any kind of up and down play. i found out from the previous owner that it ran quite, all be it crappy. he said he had burnt out a power pack, and replaced it, and burnt the other one before it ever hit the water. what shuld i look for that may be burning out the power pack.

p.s.
i am also going to start a new thread for this one.