TOPIC: I found the pinging noise

I found the pinging noise, piston slap. Hole three had only 95 pounds compared to the other 5's 127 plus or minus 5. I removed the intake side plate and the piston slows some scuffing the first ring is mostly free the second free the third stuck. So here is the question what to do? Do I run it and if so what happens or pull it apart and replace piston and rings and hone the hole to seat rings. The problem was before I owned it so I have ran it awhile like this. If i decide to replace where should I get the parts. It a 72 115 with high domes. Gotta say I did a 61 80 direct reversing for the Custom Craft and it was and long day. I just wanna get back on the water but hate to ruin a good motor worse that it already is. got the cylinder socking in sea foam not but don't expect much. Any insight would be great. thanks Mike

Me personally, id continue soaking it in SeaFoam for a few days to try to free those rings up then maybe run it in the driveway a bit to see if your numbers come up at all in that hole. If they dont, i wouldnt run it anymore than you already have.

If the cylinders scored though, which it probably is, youll probably be looking at a teardown...no fun!

sounds like you are at a point that if you did tear it down to replace the piston your current damage is minimal. if you keep going you will toast it even further. if it is a throw away motor for you then sure soak it and use it until it it blows but remember if you are in the middle of the bay/lake/harbor you can not walk home.
If you want to save the motor then pop the head and get into it.

Wrist pin bearing can give you the same noise. One way to check if it is the wrist pin is pull the plugs and put a screw driver or something like it in that cyl and bring it up to top dead center by hand then turn it over a 1/4 turn. then take the screw drive and push in if you hear a clunk or feel it go clunk you got play in it.
Mike pathfinderz1

JerrfyLube wrote:

Me personally, id continue soaking it in SeaFoam for a few days to try to free those rings up then maybe run it in the driveway a bit to see if your numbers come up at all in that hole. If they dont, i wouldnt run it anymore than you already have.

If the cylinders scored though, which it probably is, youll probably be looking at a teardown...no fun!

Look for PB BLaster...Small Engine tune up..in spray can....
Local Boat Mech recommended using it...frees up carbon deposits and sticky rings.....just take out plug spray for 10-15 secs and let it soak.

I am tearing it down pulled the power head tonight, tomorrow split it. I ordered the piston and ring should be here Monday and with any luck running Tuesday. I just couldn't waste this motor so I will that the time and do it right. If compression comes back over 100 I will be pleased.

67sears wrote:

I am tearing it down pulled the power head tonight, tomorrow split it. I ordered the piston and ring should be here Monday and with any luck running Tuesday. I just couldn't waste this motor so I will that the time and do it right. If compression comes back over 100 I will be pleased.

Wise descision!! Make sure you check the piston ring retaining pins and wrist pin clips. Give it a good hone.

Question for the engine builders since it follows this thread...

Youve got 127 in 5 holes and 90 in another. If you replace the rings and hone that cylinder out, hopefully raising your compression...would it cause problems if that one particular cylinder went up considerably...say to 140-150?

JerrfyLube wrote:

Question for the engine builders since it follows this thread...

Youve got 127 in 5 holes and 90 in another. If you replace the rings and hone that cylinder out, hopefully raising your compression...would it cause problems if that one particular cylinder went up considerably...say to 140-150?

No, Mercury actually recommends boring just one hole if needed. After honing, I don't think you would have that drastic a jump in compression.

Interesting.

Please keep us updated on how it goes! Curious to see how much the compression comes up.

I never understand that 'one bore' bit when it comes to rings? Yes, I see you can just change one piston if the bore will take a hone, but on an old motor with unknown hours on the clock it just doesn't make any sense to me to just hone & re-ring one hole. Do all of them I say then you have peace of mind regarding your pistons & rings. As others have said check everything else out while it is apart. It is a lot of work to do what you are doing & you want to get it right so you don't have to do it all again.

My ten bobs worth,

Geoff UK

little later getting to work on it because I didn't receive the right parts till last night. So I check clearence on all six and 5 were out of round by a .001 to .002. The problem hole was .0025 after honing a slight rub in the wall. Piston to wall clearence was with in spec on all, so continued the rebuild( or fix). So here is where I am at. All holes honed for new rings and a new piston in #3. The crank was in stalled least night, all carbs were cleaned and rebuilt. The distributor reinstalled and everything torqhed. So tonight I am gonna replace it on the lower leg finish I wiring and fuel linkage ect. I will hope to post some numbers soon. PS the #3 piston was toast rings locked in.

Good evening, Mike.

I've been reading your posts about the "pinging" noise with growing horror, as my 1964 650 has developed a similar noise when it's above 4500rpm all the way to redline..it's a very high pitched ping or clacking noise, two or three every second but it doesn't occur every time. I did a compression test and all 4 cyls. were the same at 128psi dry. Mr.Bernard had suggested that it might be a cracked flex plate, but it's solid and rings nicely when struck. The motor behaves normally, no surging or missing but it's scaring the s##t out of me 'cause I'm not really a mechanic, and parts and even gaskets etc are hard to get up here in Ont. It fires on the first compression, the timing is as close as I can get it(no dwell plate guage thingy), I've checked it with an old dwell/tach/points checker from Micronta that dad used to use. The scale goes to 45deg. and thats where it is.(book says 48deg.) The noise started last fall after my points lost their gap due to me not tightening the set screw down enough. Points were shot, etc. All mag parts are now new, though.
Could you maybe fill me in as to what you experienced sound and performance wise, and if you had any other ideas??

Many thanks..

John

frolic
if your pinging/rattling noise started immediately after you changed your points Id be more inclined to think your issues is pre-detonation ping from advanced timing.

pinging at the rpms you posted and is it usually during accelleration?

check your points again before you get to excited
you can make the timing gauge from a spark plug

Thanks for the reply, good sir.

The pinging started that last infamous trip last fall, when the points started to close off. We were 12miles from the wharf and we had to limp home, with the poor girl missing and stuttering and yes starting to make this horrid noise. It makes the noise above 4500rpm, either at steady state or accelerating. My tach registers a steady 5250rpm wot, and Dad's old meter clipped on registers the same, so i think it's pretty accurate. I did set btdc with a very cool dial gauge from Mr.Bernard, and subsequent max advance etc. as well as carb sync. When I set my point gap with my brass blades, I went on the sticky side of .0010(book says .0010plus 0/minus .002) and this yielded my 45deg. according to the old meter.
Thank you for posting the dial plate and directions for making it. I'll do my best to replicate it and give it a try. I do have the proper Merc. manual (courtesy of my lovely bride at Christmas) so it should be able to walk me through the process. I'm stripping the mag. down this weekend to double check points etc. (cause I don't trust myself fully yet)

Thanks so much, again.
I'll post when I have an idea....

John

Frolic

thread the inside of an old spark plug to accommodate a bolt so you can count the number of turns to find your timing spot BTDC

I finished the power head and made a test run here are the results. Cylinder #3 the one with stuck rings started with 75 pounds compression dry. The ring stuck do to the piston swelling in the bore and scuffing the piston. This was cause by a piece of rubber hose in the main jet very small but when rebuilding the carb it was found. I guess it came from the new primer installed this year or the fuel pump either way it was the root. After a new piston in #3 and new rings in all the compression was 128 and almost even across the board. So I test drove the boat and ran a solid 40 mph and found that I an gonna need a prop change because it was trying to over rev. I had to hold back to keep it a 5500 so the refresher was a success. By the way the ping rattle noise is gone plus it seems to use less fuel.

67sears wrote:

I finished the power head and made a test run here are the results. Cylinder #3 the one with stuck rings started with 75 pounds compression dry. The ring stuck do to the piston swelling in the bore and scuffing the piston. This was cause by a piece of rubber hose in the main jet very small but when rebuilding the carb it was found. I guess it came from the new primer installed this year or the fuel pump either way it was the root. After a new piston in #3 and new rings in all the compression was 128 and almost even across the board. So I test drove the boat and ran a solid 40 mph and found that I an gonna need a prop change because it was trying to over rev. I had to hold back to keep it a 5500 so the refresher was a success. By the way the ping rattle noise is gone plus it seems to use less fuel.

Good deal!! Glad to hear ya got it all straightened out!

so the refresher was a success. By the way the ping rattle noise is gone plus it seems to use less fuel.

Nice

That's good news for sure. Prop change due to new power found isn't so hard to justify, right!?

Well done, that's a really good feeling isn't it?

Geoff UK