Mercury Outboard Help.
Posted: Mon Aug 01, 2011 11:38 pm
Need some help with my 3 cylinder 65 HP mercury outboard with power trim.. i believe its around mid 70's engine. has a plastic cowl not the metal one found on pre 70's.
Bought my boat 2 years ago with this engine. fired right up but was leaking water out of the side cover. so i bought gaskets and tore it apart to find it was cracked inside and water getting into the crank through the exhaust side.
So i went to a friends who works on boats and he happened to have a whole 70 HP stripped apart in a box, the head and pistons are the same as the 65 HP, the extra 5 HP came from different carb jetting and newer electronics that got rid of the distributor. So i used the 70 HP head put the best looking pistons i had from the 2 engines into one and got it back together and wouldnt start. Key on not turning it over you could hear it sparking randomly in the distributor cap, i messed around with it for a while and never figured it out and gave up for the season.
Last summer i never even touched it.
This year i got back at it and throw a battery in it and it fired right up but ran rough. i got browsing online and found a whole engine the same for 100 bucks with low compression on 1 cylinder. so i bought it and put all the electronics onto my engine and it ran great in the back yard. i done a compression test on it... 150 psi on all 3 cylinders.
Finally got it in the water this past weekend, wouldnt rev past 3,000 rpm on the water but sounded to be running smooth, just didnt want to go anymore. after a few runs around it opened up and just screamed across the lake then would slowly die back down but never failed on me.
Went back out again Sunday and same problem, so i thought maybe bad plugs, pulled them out and found one that was loaded with crud. cleaned it up and way i went just screaming again for 5 minutes then slowly die down again.
When i got home i ripped the engine off tore it apart and found the top cylinder.. (#1) the piston was starting to melt in the center and had bad scoring on both sides. not exactly sure what the problem was.. i just put a new water pump in it and it works great so i dont think it was overheating.
.......
my Theory of the burn piston is leading more towards the timing not being correct.. too far advance possibly causing pre ignition, but its only the one cylinder thats bad..
.........
I tore down my spare parts engine i got this summer. and only had slight scoring on 1 cylinder so i ran my hone through it and cleaned it up, still some marks in it but its 100 % better then it was.
All the pistons have 3 rings in this engine.. the parts engine had 1 new looking piston with only 2 rings and the gap in a different location and a chip out of the ring so im assuming it was catching on a port.
I took the 2 good pistons from the blown up engine and put into the parts engine today, finally got it all back together, what a PAIN.. lol. the worst part is getting the pistons back into the head i done it all by hand, even if you had a tool for the rings you would not get it down in there because the head and one side of the crank case is 1 piece so its pretty tight getting even your finger in there to push the rings in. and changing the pistons is a nightmare LOL, the wrist pin bearings are all separate little needle bearings that are not in a raise so i load them up with grease to hold them in place while getting the wrist pin pushed back in then you have to check that the dam things didnt fall out LOL.
So after all this.. got everything all back together, primed the gas, touched the key and way it went, but i couldnt pull the throttle all the way down where it normally would be at an idle or it would stall out and start pinging.
I am not sure exactly how to set the timing on this thing.. it has a distributor that runs off a belt to under the flywheel, it does have a timing mark on it, when the mark is lined up #1 is TDC but for it to run i have to advance the throttle way up as to advance the timing.
So i tryed this..... took the belt off, turned the distributor gear 1 took back. Did run but was worse. so i took it off and put it one tooth forward. and now it runs MINT. ..
Sat there and idled for 2 hours while i was cleaning my mess up, took the plugs out to check for junk on them and still clean so i guess i done something right LOL.
The help i need is how to set the timing properly on this thing so i dont burn up more pistons or do other damage and kill this engine.
The throttle lever at the same time also advances the timing as you throttle up, but as some point the timing has to stop advancing it has screws to turn in and out for where the spark advance should stop.. im pretty sure the timing at idle is pretty dam close to being right on, i have a spare distributor and sat beside the engine looking at where it would be firing. so with the timing actually 1 tooth on the gear (belt) forward i think im retarding the timing. its firing either right on TDC or just slightly after. Previously i think it was firing before TDC
The way it was before i left it lined up with the marks and adjusted the crap out of the advance lever so it would run and i think this is why i burned that piston out of it. i want to make sure this is right before i get it out on the lake and run it full board.
If anyone knows about older mercury outboards chime in and give me a clue please LOL.
this engine is on a 15 foot V hull boat. 76 inches wide just a little runabout. it seems pretty fast. the prop on my engine was a 15 pich. the spare engine i got had a MINT 22 pitch so i put that on. for $100 i paid for the other engine the prop was worth that. but in the end i ended up having to fix the spare motor and run it now.
Ill get a few pictured up tomorrow of the engine to show more about the timing crap on it. i was hoping maybe someone would have manual or know more about these mercurys then i do, actually i dont know very much about it LOL, first outboard i have ever stripped down to nothing and put together. but not my first engine or first 2 stroke. im pretty handy with anything that has an engine, and pretty much anything else lol.
Bought my boat 2 years ago with this engine. fired right up but was leaking water out of the side cover. so i bought gaskets and tore it apart to find it was cracked inside and water getting into the crank through the exhaust side.
So i went to a friends who works on boats and he happened to have a whole 70 HP stripped apart in a box, the head and pistons are the same as the 65 HP, the extra 5 HP came from different carb jetting and newer electronics that got rid of the distributor. So i used the 70 HP head put the best looking pistons i had from the 2 engines into one and got it back together and wouldnt start. Key on not turning it over you could hear it sparking randomly in the distributor cap, i messed around with it for a while and never figured it out and gave up for the season.
Last summer i never even touched it.
This year i got back at it and throw a battery in it and it fired right up but ran rough. i got browsing online and found a whole engine the same for 100 bucks with low compression on 1 cylinder. so i bought it and put all the electronics onto my engine and it ran great in the back yard. i done a compression test on it... 150 psi on all 3 cylinders.
Finally got it in the water this past weekend, wouldnt rev past 3,000 rpm on the water but sounded to be running smooth, just didnt want to go anymore. after a few runs around it opened up and just screamed across the lake then would slowly die back down but never failed on me.
Went back out again Sunday and same problem, so i thought maybe bad plugs, pulled them out and found one that was loaded with crud. cleaned it up and way i went just screaming again for 5 minutes then slowly die down again.
When i got home i ripped the engine off tore it apart and found the top cylinder.. (#1) the piston was starting to melt in the center and had bad scoring on both sides. not exactly sure what the problem was.. i just put a new water pump in it and it works great so i dont think it was overheating.
.......
my Theory of the burn piston is leading more towards the timing not being correct.. too far advance possibly causing pre ignition, but its only the one cylinder thats bad..
.........
I tore down my spare parts engine i got this summer. and only had slight scoring on 1 cylinder so i ran my hone through it and cleaned it up, still some marks in it but its 100 % better then it was.
All the pistons have 3 rings in this engine.. the parts engine had 1 new looking piston with only 2 rings and the gap in a different location and a chip out of the ring so im assuming it was catching on a port.
I took the 2 good pistons from the blown up engine and put into the parts engine today, finally got it all back together, what a PAIN.. lol. the worst part is getting the pistons back into the head i done it all by hand, even if you had a tool for the rings you would not get it down in there because the head and one side of the crank case is 1 piece so its pretty tight getting even your finger in there to push the rings in. and changing the pistons is a nightmare LOL, the wrist pin bearings are all separate little needle bearings that are not in a raise so i load them up with grease to hold them in place while getting the wrist pin pushed back in then you have to check that the dam things didnt fall out LOL.
So after all this.. got everything all back together, primed the gas, touched the key and way it went, but i couldnt pull the throttle all the way down where it normally would be at an idle or it would stall out and start pinging.
I am not sure exactly how to set the timing on this thing.. it has a distributor that runs off a belt to under the flywheel, it does have a timing mark on it, when the mark is lined up #1 is TDC but for it to run i have to advance the throttle way up as to advance the timing.
So i tryed this..... took the belt off, turned the distributor gear 1 took back. Did run but was worse. so i took it off and put it one tooth forward. and now it runs MINT. ..
Sat there and idled for 2 hours while i was cleaning my mess up, took the plugs out to check for junk on them and still clean so i guess i done something right LOL.
The help i need is how to set the timing properly on this thing so i dont burn up more pistons or do other damage and kill this engine.
The throttle lever at the same time also advances the timing as you throttle up, but as some point the timing has to stop advancing it has screws to turn in and out for where the spark advance should stop.. im pretty sure the timing at idle is pretty dam close to being right on, i have a spare distributor and sat beside the engine looking at where it would be firing. so with the timing actually 1 tooth on the gear (belt) forward i think im retarding the timing. its firing either right on TDC or just slightly after. Previously i think it was firing before TDC
The way it was before i left it lined up with the marks and adjusted the crap out of the advance lever so it would run and i think this is why i burned that piston out of it. i want to make sure this is right before i get it out on the lake and run it full board.
If anyone knows about older mercury outboards chime in and give me a clue please LOL.
this engine is on a 15 foot V hull boat. 76 inches wide just a little runabout. it seems pretty fast. the prop on my engine was a 15 pich. the spare engine i got had a MINT 22 pitch so i put that on. for $100 i paid for the other engine the prop was worth that. but in the end i ended up having to fix the spare motor and run it now.
Ill get a few pictured up tomorrow of the engine to show more about the timing crap on it. i was hoping maybe someone would have manual or know more about these mercurys then i do, actually i dont know very much about it LOL, first outboard i have ever stripped down to nothing and put together. but not my first engine or first 2 stroke. im pretty handy with anything that has an engine, and pretty much anything else lol.