Worn cam or bad lifter

[s.hadley81]

To make a long story long my mercruiser 89' 120hp I had a problem with water in the cylinders (blown out riser gasket) I got that taken care of and oiled and dried it but I've been having a problem with acceleration it just kinda breaks up and hesitates, it will reach wot after a little bit and would pop through the the carb ,not bad but it did pop back a couple times, when trying to find this problem is when I found the water intrusion so I thought that was the problem but it wasn't , since then I've completely ruled out fuel because my carb was just rebuilt and I cleaned and double check my float plus it ran fine after rebuild, I replaced filters , new fuel pump , I ran on remote tank , I checked timing and distributor advance weights so I pulled valve cover to have a peek figuring something mighta bent trying to compress water and everything looks great , all valves move,and no play ,so I read online a trick is to mark the pushrods and see if they turn to check for bad cam lobe or lifter, all did except #1 exhaust i think, I gotta double check the book to see if it's exhaust or intake valve, so I pulled that push rod and it's fine and straight, I was wondering if anyone ever heard of marking the pushrods and checking for rotation, I also forgot to mention I tested compression and all 4 are around 145psi that's good and after thinking about it an exhaust valve not opening fully would make sense as that's how the motor felt like its being choked, my other question is would a piston trying to compress the water wipe a cam lobe or collapse a lifter without bending the rod , sorry for the long winded post I just wanted to put as much info out there as I could think of and post everything I found out so I could get some input before I pull the head

Thanks a lot in advance

P.s I also drained my oil and there was water in it (not much at all maybe 4oz ) And after fixing the riser gasket it's clean so I strained the oil and cut open the filter and no metal just a tiny bit of crud nothing outta the norm,another thing I didn't mention was it only acts up under a Load in the water, sorry having a hard time trying remember everything I went through

 

[nateo]

I've been trouble shooting similar problem with my boat recently.

Before you pull that head...Backfiring through carb is usually ignition related. Are you sure your timing is correct? Ideally boat needs to be in forward gear idle at the proper rpm and make sure timing is correct. correct timing specs usually are on a sticker on the valve cover or something. You'll probably have to look up the rpm, mine is 650-700. having correct rpm when you check timing is key. how's the idle and at what rpm? Sounds ignition related.

When you tighten down that rocker that you removed make sure you're on the correct tdc stroke.

 

[s.hadley81]

Thanks for the reply, my timing is right the boat ran like a top before the water intrusion my idle is perfect around 700 ( it was rough with water in the cylinders but I set it and timing in the water in gear and as far as the rocker I tightened it but didnt set it yet as I still have the motor apart and I'm not ready to fire it yet but it will be adjusted right this I think has to do with the water getting in the cylinders I'm pretty sure because I basically brought this motor back from the dead and it ran like a ...... Date before the water in the cylinders

Thanks a lot

 

[nateo]

idle air fuel mixture screws set properly? what kind of carb is it? I worked out a similar issue last year everyone kept saying "lean sneeze". Ended up being a combination of properly adjusting idle air/fuel mixture screws, idle screw, and timing to fix. With mine I figured out the previous owner bumped up the idle just a wee bit (due to a shift cable issue) and it threw everything off. I kept trying to set the timing at 700 instead of 650. mine runs properly at 650 with occasional bumps near 700.

 

[s.hadley81]

Everything was set and the boat ran perfect all season long till I ingested water about two weeks ago and running lean was the first thing I looked im almost sure this is in the valve train

 

[s.hadley81]

Tomorrow I'll pull the lifter out on the valve that the pushrod is not spinning because I'm almost positive that's where my problem is after doing some reading that pushrod should spin but hopefully it's the lifter and not the cam

 

[flipbro]

Your absolutely correct. The lifter should spin. If it isn't its a very good chance your cam is toast not the lfter

 

[s.hadley81]

Thank you very much that's what I thought now would I be able to put in a used cam or do I have to get a new one I didn't know as far as the way everything wears

 

[s.hadley81]

Also I did verify it is the exhaust valve on cylinder #1

 

[s.hadley81]

The reason I'm thinking of using a used cam is because I can get one real cheap and a new set of lifters are cheap so I could possibly put a new (used ) cam and lifters for around $100, I can hunt down a used 120 or for probably a couple hundred so I don't wanna throw a bunch at this motor but I'd rather fix this one because it was a pretty tight motor till I got water in the cylinders, I would think if I got a good (used ) cam and new lifters and broke in as a brand new cam I would be ok, but I never tried it

Thanks

 

[flipbro]

I wouldn't go used. Thats just asking for problems.when I rebuilt my engine I got a new cam with lifters for 100 bucks off ebay..

 

[s.hadley81]

I pulled the pushrod/lifter cover and pulled the two lifters on #1 and inspected the cam visually and both lobes look about the same (I know I can't go by that just don't wanna pull the cam yet just yet) also both lifters look good and the foot on the one in question Appears to be ok no signs of wear so if my cam is indeed worn shouldn't I see that on the lifter foot meaning uneven wear

 

[flipbro]

Not necessarily. A flat tappet cam has a slight slope on the lobe.thats what makes the lifter spin. You can have a bad lobe qnd lifter look fine.did the lifter in question come out of its hole easily?

 

[s.hadley81]

Both lifters came out very easy they just slid right out can I switch the two lifters and spin the motor over with the starter (not running it) and see if problem moves to the other valve or is mixing lifters that touchy

 

[flipbro]

You could just to verify its the cam. Or lifters. But in the end you will find out its the starts of a cam lobe rounding off..But for sure do the test to be 100 % sure

 

[Eric 3.7LX Alpha 1]

deleted

 

[alldodge]

it will reach wot after a little bit and would pop through the the carb ,not bad but it did pop back a couple times,

IMO, you may or may not have a cam, lifter issue, but with your symptom your running lean.

 

[flipbro]

Alldogde is write is does sound like a lean condition. But the lifters and push rods not spinning is a problem aswell and if a lobe is going bad it would cause a lean pop

 

[s.hadley81]

So I finally got back around to messing with the boat,while I had the two lifters out for cylinder #1 I worked the plungers up and down on the workbench and realized the lifter I thought to be bad the plunger stuck down every once and awhile, so I took it apart and cleaned I then soaked them for 2 nights in oil and put them back in, adjusted the valves and cranked the motor with the plugs out, now my pushrods are definitely spinning on both intake and exhaust so while it's open I'm gonna put a new set of lifters in I did have a slight tick at the back of the motor so maybe I'll lose that in the process so my question now is would I be right by soaking the new lifters then I have comp cams cam and lifter installation lube I'm gonna put on the new lifters and I also got a bottle of Lucas oil engine break in oil additive (TB zinc-plus) made for flat tappet cams that I'm gonna put in the oil and just treat the new lifters like I'm breaking in a new cam by holding a 1500-2000 rpm fast idle for about 20mins does that sound like a solid plan or am I missing something else I should do to put in new lifters and also I just wanna say thanks again for all the advice and info as I've never had to tear into the motor this far (hopefully not again for awhile) and all the input has really helped me get through this

 

[s.hadley81]

I also got a real good look at the lobe on the cam with an inspection camera while cranking it over with a remote start switch and the cam and lobe look great i can't see any signs of wear whatsoever