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merc 350 engine noise help

guyjg said:
Did you use a timing light to set the timing? Are the carb mixture screws set at 1.25 turns out from fully inward?
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I have a good professional mac timing light I borrowed. I cannot get the thing to idle. It will run at around 1800 or more rpm. But is backfiring fuel out the carb something fierce. my son and I just reset to tdc and I checked and re-aligned the distrubutor.
 
guyjg said:
Did you use a timing light to set the timing? Are the carb mixture screws set at 1.25 turns out from fully inward?
Click to expand...

ok i screwed them all the way in. then turned 1.25 out. still backfires.
should i advance or retard the timing so it will idle? or should i have the motor popping and spitting and then turn the distributor
 
Dan this motor on a stand or pallet ?

I just re-read the whole post, This motor is sounding more and more like a cluster f.

Rap the carb on the fuel inlet fitting, with the back of a hammer. The wood end not on the fuel line the fitting. Or tap the top half of the carb.

That dislodge the float. But me i like to take the carb off and rebuild it takes less time fiddling with a carb thats acting up.

The timing is a different story and the valve issue.

This motor would be sitting on a pallet if i was messing with it.

Water issue alone would make me want to drain the block and turn it over to see whats with the main bearings, oil pump, pushrods, wristpins in short everything on the bottom end is good.

I mean you say you went thru everything, i keep reading and reading the thread over and over i can't get my head around this.

Me this motor would have been running ,timed ,and purring as well as i could get it on land.

It should idle in the water, in gear worm 600-700. That means maybe 800-850 on land. You will loose 150 rpm's at least on the water, then fine tune final idle as started above.

So we want idle on land 800-850 no popping backfiring.

The plugs have to be looked at.

Good luck ! I know this was a long post but we have to set a goal.
 
chiefalen said:
Dan this motor on a stand or pallet ? It's in the boat....

I just re-read the whole post, This motor is sounding more and more like a cluster f. It is!!!!

Rap the carb on the fuel inlet fitting, with the back of a hammer. The wood end not on the fuel line the fitting. Or tap the top half of the carb.

That dislodge the float. But me i like to take the carb off and rebuild it takes less time fiddling with a carb thats acting up.

The timing is a different story and the valve issue.

This motor would be sitting on a pallet if i was messing with it.

Water issue alone would make me want to drain the block and turn it over to see whats with the main bearings, oil pump, pushrods, wristpins in short everything on the bottom end is good. I did have the motor out. replaced all cam shaft bearings and inner seals-pushrods are fine and oil pump is pumping. wrist pins, and pistons all looked good. Remember this engine once installed only had 1 day outing!!!!! thats it. Then I winterized and put away for the winter. problem was all of the water had not drained out which seized the block. Thats why I took apart last summer, had machine shop polish the internals, they put the seals in. then I put it back together. Only thing I had not replaced were the lifters because they looked fine. they were not marred or rusted or anything. I figure just a couple must have been messed up from the water. I also changed the exhaust manifolds prior to starting up this summer.

I mean you say you went thru everything, i keep reading and reading the thread over and over i can't get my head around this.

Me this motor would have been running ,timed ,and purring as well as i could get it on land. The motor ran fine prior to replacing the lifters.....so I am thinking it must be a distributor mess up on my part. Even thought I double checked the wiring. And I double checked that #1 was in top dead center and the dist was pointing at number 1, and the cap was turned and set at the #1 plug wire.

It should idle in the water, in gear worm 600-700. That means maybe 800-850 on land. You will loose 150 rpm's at least on the water, then fine tune final idle as started above.

So we want idle on land 800-850 no popping backfiring.

The plugs have to be looked at.
Inside of the plugs look fine, not even much carbon due to the low run time. My friend says to bring it to his shop and he will have a mechanic check the firing order etc. I will take it there Saturday am. So, thanks for taking the time to help trouble shoot I dooo sooooo appreciate it.
Good luck ! I know this was a long post but we have to set a goal.
Click to expand...

A boat is a hole in the water that sucks your wallet dry!!!!!!!
 
Sounds to me like you need to pull #1 plug and bump starter over with finger in hole until you get compression to verify #1 tdc you may have distributor 180° out which would be #6.
 
akdad said:
Sounds to me like you need to pull #1 plug and bump starter over with finger in hole until you get compression to verify #1 tdc you may have distributor 180° out which would be #6.
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I beleive you may be right. When my son and I did it last night. He was the one with his thumb over the hole. So perhaps he was wrong. Hope thats all it is when I take it in Sat......I am sooooo ready to be on the lake with these hot ass days!!!
 
alrighty here is an update for those that may have a similar problem. put the newest fuel pump. took it to my friends shop and a mechanic help me re-set the valves and timing - we used a compression guage to make sure it was tdc. He was young and works with his dad, but he was free and free is always good ;). next day wife and i took it to the lake, we puttered around for 20 min to break in the new lifters. Then I started to slowy give it throttle. well, about 2700 rpm the backfiring noise is back. but at least i was able to give it more power than before and get the boat on plane. I believe the backfiring is due to improper timing. when he set it, the engine was idling at 2k rpm. he didnt back off on the throttle set screw (and i didnt think of it). so the timing was not set at 800 rpm idle. taking it out tommorow if it doesnt rain, armed with timing light. I was able to screw the idle down to 800. My other concern is if the timing doesnt fix the backfire. then i beleive i need to take the covers off again and reset the valve lash one more time.
 
I reread this whole thread again. There is something off, be it the timing chain, timing gear, cam, something and no amount of messing with the dist gonna fix it.

Bear with me a sec, and consider this, no water in the fuel carb good, dist good, got to be something else.

Pull the timing chain cover, start there.
 
Thanks Alan for following the post. Well I had a thought, wanna run it by you. The fuel is over a year old now that i think about it. I think I need to just take a 5 gallon tank and plug the fuel pump hose into it. I dont think thats it, but its an easy try to elimenate the fuel. I just dont see how that could make it sound like a backfire. What do you think?
 
went back and did the valve lash at 1/4 turn instead of 3/4 per the manual. its still making popping, tapping sound from the carb. Also, it does not have any power. at 2k rpm the boat starts to rise, then i gave more gas, but it wont plane out. hmmmm distributor? would wrist pins be quiet while idle and low rpm, then make noise under load? (i didnt remove them from the pistons originally).
 
I did not read through everything posted so if this has been covered,sorry.

If you ever use old rods they need to be trued by a machinist.This may or may not be a lifter issue,wrist pin etc.

If it has nothing to do with the bottom end then suspect the top end,heads(valve train).

If the machine shop did the build then I would ask them to take a peek,the problem could be a number of things.

Check list,
bad crank or main bearing tap
rod bearing or wrist pin
rocker arm or lifter/flat spot on the cam
cam bearings.

Could be a fuel pump,not able to hear the sound,could be in the dizzy.

Scope it to find out if it is top or bottom.
Then the guess work would not be an issue.


Edit just heard the video.
That is not a timing issue,sounds like a knock.

Scope it,could be in the bearings,rod may need to be trued up or wrist pin.
Fix it before your looking for a new block.
 
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Well, the final say is its the cam shaft. So now, I can replace it without removing the engine. but i guess the question would be, do i need to pull the motor and remove the oil pan for any shavings? Or would draining the oil and changing the filter be sufficient??? thanks to all that have been so helpfull and followed my journey!!!!!
 
Ok fellows, today i took the timing chain off. the 2 dots were not exactly perfect, off by an 1/8 inch. then I took the camshaft out (carefully) and after inspection, non of the lobes are worn. i measured them all. took to mechanic friend and he said lobes look fine but the bearings look like they might be a little worn. To mee they looked no different than the new one I purchased. So now I am at a loss for the problem. when I had the engine out the first time, i had machine shop put new cam bearings in for me. So I am just not sure how to proceed at this time. please chime in fellows...thanks Dan
 
Alright, so here is whats up now. I changed the ignition control module becuase it was bad. Fired up the boat after fixing the timing chain. set the timing to 8 btdc, ran and adjusted the valve lash. took it out to the lake yesterday and was hard keeping it running, adjusted the set screw to keep it running. then gave it a go and when I give it alot of throttle, I have no power and the engine seems to be shaking a bit. Is this a timing issue? or something else. hope someone can let me know this weekend. Cause I think I am ready to take it to a boat mechanic!!!!!
 
about the carb, its getting gas fine. if i was on the lake with a helper, what would i look at to see if theres a problem? it is a 4bbl carb. as far as the advance on the timing. I did not advance it with the gun because i was by myself. It was so hot out there I didnt feel like shooting the timing light (in disgust with heat not a good thing. and i couldnt get wet cause had surgery). I am thinking a mechanic may not charge me an arm and leg to determine the problem....what do you think??
 
danthemancarolina said:
Had a noise in my 350 mercruiser. i took the engine out and did what the manual described to fix. my camshaft is fine, lifter were fine, rods fine,piston rods fine. I took the block to a machine shop to polish (it originally got water in it from the exhaust manifold-replaced now). replace all of the rod bearings. replace the main camshaft bearing. (non looked slipped but thats what the book said).

now, it will start and idle fine. but when i add a little rpm, i get the same darn ticking noise. well its more of a really loud tapping noise. i really dont thnk that its valve lash since it was making the same sound prior to rebuild. I did not have the heads redone, maybe a valve is stuck, or maybe one of the lifters have sunk? geez this is really ticking me off...
Click to expand...

to see if the lifter is stuck add 6oz of marvel mystery oil to the crankcase and let it idle for an hour see if it reduces or fades.

after listening to the utube video sounds like a piston , thats not lifter noise.
 
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Most only concern themselves with setting base timing when the most import timing variable is the advance. You must ensure that you are getting a propper advance curve (check your manual) so that you can set any doubts about the ignition system aside. After you are sure the timing is up to spec (proper base setting at specified idle RPM and reaching total advance), then you can move on to other systems if the problem still persists. While the timing light is still attached, go for a spin with someone and bring her up to the point when you can just start hearing the knock. Compare the knock with the flashes from the timing light. This may take a while but you'll get it eventually. If the knoking is about the same frequency as the timing flashes, the problem is the upper end or valve train. If the sound is double the frequency or two knocks for every flash, the problem is the lower end; crank, piston etc. You can even try moving the light's pick up from one cylinder to another to see if you can get an exact match, that will tell you which cylinder is the culprit.

Have a bad feeling though. Hard to tell from here looking at the video but almost sounds like a piston slap. Hope I'm wrong.
 
Woodieman, thanks for your thoughts. so a couple of things for all that are reading and helping #1 thanks a bunch! The noise seems to be gone since I re-did the timing chain. Now its just the power issue. I looked up the timing info in the book. initial is 8btdc. the advance should be 32btdc @ 3700 rpm. How do I measure the 32 when the tab on the engine block only goes to 12???
 
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