Mercruiser IO, Loss of power

[rodbolt]

Re: Mercruiser IO, Loss of power

hello<br /> Bob G<br /> check your water seperator. unscrew it and dump it in a clear container and look for water or orange jelly looking stuff. if there is very much,it may have passed water to the carb. several things will make it pop back though the intake system.a lean condition due to lack of fuel in the carb or water covering the mainjets. ignition timing that is incredably advanced or retarded. not likely while your just cruising about. the timing cant just out of the blue jump tooth. mechanical things break not just jump one tooth and continue. a broken intake valve spring will cause that problem as well but is very difficult to find due to the fact that at low speeds the damper spring will usually close the valve.late valve timing may cause the fire to still be lit when the intake valve opens or a flat cam lobe will cause this. a cam lobe wiping out usually makes the engine oil glitter. if you have the oil filled coil then shade it or in the dark look for arcing from the coil secondary tower to the coil primary terminals. dont take the splatter approach to trouble shooting. do not try to power time the engine. use the service manual to verify specs. if you suspect a timing chain issue there is a method of testing in the manual. late valve timing usually causes low and steady intake vacum. a brokne valve spring will cause it to be erratic. all the info on using a vacume gauge as a diagnostic tool is in the manual.by the way where was the timing set before you started moving the distributor about?<br />timing gets blamed for many problems but is rarly the problem on a modern ign system until a component fails. my bet will be a valve train or valve timing issue or just plain old water in the carbs. good luck and post us with any questions or comments. I used to work up that way but not anymore so I cannot give ya any advice on a tech in your area anymore. most the good ones I knew either like me, they dont take on new customers or they moved on. dont even think about the gimbal. it will twirl like a pinwheel if it locks to the shaft. I dont know who at merc made a suggestion like that but it shows they are grasping straws and its time to leave

 

[n-4ih]

Re: Mercruiser IO, Loss of power

Bob G. et al, I hauled for the season today. My mechanic had run the boat yesterday and had the same symptoms occur for him. He had to limp back to his shop at idle speed. As mentioned in my first post (yesterday), three plugs looked burnt. He showed me a Champion publication that had pictures of problem plugs. Mine looked exactly like ones suffering from pre-ignition. The one he showed me had a bulbous end to the protruding electrode with a way-too-wide gap and a burned out center electrode. He's guessing that the cylinders have "hot spots". May be correct; I tend to run slow a lot more often than fast. I could be getting carbon buildup on the cylinder walls. I don't know how this would fit in with his first thoughts about low compression. I don't think it's a wire problem, but I trust my mechanic to verify that. I also doubt if it's endemic to just our model. Based on your first post, your boat is probably lighter than mine (2000 had a design change). We seem to have the same engine/outdrive but my WOT RPM was stated as 4400-4800. I could get that only after switching props. But it is also obvious to me that my boat is underpowered with that motor. My top end (per GPS) is only about 30kts (on a GOOD day!). My mechanic can't get to work on it for a few weeks. I'll update you then. BTW Bob G. there are other coincidences: I tried to register as "Bob G" but that was taken. And I'm in the CGAux with a son in the USCG, also named Bob G.

 

[skyking_22]

Re: Mercruiser IO, Loss of power

Found out what the problem was. If only they had diagnosed it 3 1/2 years ago when this started it might not have cost me $5600.00. My engine has 4 cracked cylinders, 2 cracked heads and 2 tuliped valves. I can't beleive that all of those compression tests the deal performed were normal. I really can't beleive it even ran. I'm heading to the dealer tomorrow to make sure it is my engine and not a swap-a-roo. Thanks everyone for the support in my quest to figure out what was wrong.

 

[skyking_22]

Re: Mercruiser IO, Loss of power

New twist. The actual problem with the motor was a worn lobe on the camshaft. They had pulled the cam from my old motor to put in another boat and wala, they found the problem. I had the block and heads magnafluxed and no cracks were found. Needless to say I will see them in civil court this month. The cam only had 400 hours on it. If you are having the same symptoms check the cam. All the cylinders had good compression, or so I was told.

 

[trog100]

Re: Mercruiser IO, Loss of power

now in the good old days before oil filled self adjusting cam followers your problem would have made itself damned obvious long before it got to the stage it did..<br /><br />some things we take for granted perhaps we shouldnt.. reminds me of a car story.. a friend of mine had a single cylinder mis-fire.. i looked at it and told him he had a collapsed cam follower they have a one way valve arrangement in em and if it sticks open the follower just sqidges up instead of opening the valve..<br /><br />a couple of days later i asked him if they had fixed his car yet.. he replyed no not yet... they have fitted a new head gasket but they recon there must be something else wrong as well.. he he he<br /><br />the moral of this story is that the garage never did admit they had made the wrong diagnosis and replaced a head gasket with nothing wrong with it.. and simply said more things were wrong and of course my friend with "bad hearing" got to part with a lot more of his money..<br /><br />so what do we have here then.. sixteen camlobes that can wear.. sixteen oil filled followers that take up the cam wear and we take for granted.. hmmm.. none of this shows up on normal diagnostic methods.. its probably a far more common reason for gradual power drop offs than is ever realized.. or diagnosed.. he he he..<br /><br />trog100

 

[Bondo]

Re: Mercruiser IO, Loss of power

All through All of this, the symptoms are the Same............<br /><br />You're Running Lean..........<br />You've got a Fuel Restriction.......<br />It Could be Anything between the Tank,+ the Carb........<br />A Fresh Fuel Filter is where I'd start 1st........<br /><br />You'll have $pent $10,000.......<br />And, It's Because It's Running LEAN.........<br /><br />I Don't Think your Troubles are over Yet........<br />

As for the fuel/H2O seperator, I changed it last year, maybe time to change it again.

Ayuh....... No $h!t........ You Should have Started Here..............

 

[pine island fred]

Re: Mercruiser IO, Loss of power

Yep, check the finger filter in the fuel pick up tube in the gas tank. its the first thing in line. its a metal,( copper ? ) screen fred

 

[newport dave]

Re: Mercruiser IO, Loss of power

So they put in a new engine, then called you five months later to tell you that you didn't need a new engine? That's crazy. But no more crazy than diagnosing "4 cracked cylinders, 2 cracked heads and 2 tuliped valves" when "all of those compression tests the deal performed were normal".<br /><br />Dave

 

[f_inscreenname]

Re: Mercruiser IO, Loss of power

I don't know about you guys but the motor would have come out long before 3 and a 1/2 years and $5600.00 in repairs. I think the most of us were on the right track we just didn't go far enough. I think after checking the obvious I would have checked the valve train by running the motor with the covers off but I also rebuild my own motors. Not for everyone. What am I talking about.. I spent a bunch of time and money on my distributor, wires, plugs and carburetor retune kits to get rid of a lean timing knock I would get above 4200rpm’s. Drove me crazy all summer. It wasn't even a consistent knock. Just a ping here and a ping there. One day I pull the motor cover off and move it to the side and watched the motor at near WOT and there it was. The alternator belt was pinging off the blades on the front of the alternator here and there. It seemed the belt would flex sideways at high RPM. New belt = 6 bucks Chasing the problem = I will plead the 5th

 

[rodbolt]

Re: Mercruiser IO, Loss of power

hello<br /> sounds like your dealing with a downtown dealer <br /> a flat cam lobe is easy to detect with a vacum gauge and the knowledge to use it. but it will also show up in the compression test as slowly rising compression. the object of the test is to observe the needle and all cyls have an equal number of compression strokes not just the last number. a broken valve spring is a tad bit harder to find but a vacum gauge will still find it. and any tech that will pull a cam from one motor to install in anther should be closed down.<br /> if your atty desires a trained witness I have experience in that area as well.if it had tuliped valve faces you would have water in it as well. if the heads were cracked the same story. I have never seen a cyl crack at moderate engine speeds on a small block. I have lunced a few on the track above 7500 that cracked one when the wristpin went through it.<br /> I think someones story is rather fishy in this tale. and yes I am almost to the point of supporting a marine licenseing program so all techs have to be trained but somehow I imagine the **** poor ones would manage to get one anyway.<br /> none of what I do is voodoo nor black magic. its all basic mechanicals.<br /> a cam wont slowly wear out and flatten. the cam is normally induction hardened or parkerized. both are a surface hardening treatment and if it wears a few thousaths then the rest is very rapid.<br /> one of the major cam wipe out problems is improper storage then improper starting procedures after storage. tha lobes on a small block chebby are splash lubricated. if it sits 6 months then you grind the starter for 20 mins trying to start it there is a good chance to wipe a lobe. but all that metal goes into the oil. if you check it you would have found it had a mettalic sheen. always.so someone missed some major points in the diagnoses of the engine.<br />post us on the civil suit<br />but make sure whoever your witness is can describe valvetrain theory and back it up with service manuals and diagrams or you will lose.<br />the judge knows as much about engines as you do.

 

[deputydawg]

Re: Mercruiser IO, Loss of power

Make sure it runs good after all of this. A worn cam lobe won't allow the engine to run smooth except for the occasional backfire pop through the carb. The backfire is an intermittent symptom. The cam is a constant problem. You are not getting enough fuel. A worn cam it would NOT run smooth and occasionally backfire. You would have 1 cylinder constantly giving you trouble creating a rough idle. <br />I have scanned through this and have yet to see the carb being checked. There has beena lot of talk about timing. Timing doesn't get that far off on it's own. Wear in the timing chain and gears, and some minor wear in the distributor will cause the timing to become out of range. The only other way timing can get out of range is if the distributor gets turned. <br />Go through your fuel sustem front to back. You will find a problem there. Maybe a lack of fuel, maybe an air leak allowing too much air. <br />The 4 cracked cylinders and cracked head is ridiculous. I would demand to see your old block and heads. I can not imagine that many cracks in an engine, and it still even starting. <br />If a compression test is not done correctly it is easy to miss a cracked cylinder or head. If done correctly it should have shown up.

 

[waterone1@aol.com]

Re: Mercruiser IO, Loss of power

I have to also echo a "running lean" situation here. While several people advised to check/replace the water-fuel seperator, I didn't notice anyone suggest to replace the fuel filter in the carb inlet. Just a little bit of dirt on that filter and the engine will idle smooth and run well at 1/4 to half throtle, but will be starving for fuel when pushed past half. Too much time running like that will cause serious problems such as burnt valves.

 

[trog100]

Re: Mercruiser IO, Loss of power

badly worn cam lobes just knock of your top-end grunt.. to be honest with an eight cylinder engine i would have thought with just one lobe being worn there would not be a massive power drop off..<br /><br />i once ran (unknowingly) a four cylinder cam-in-head GM/Opel engine for many thousands of miles with its cam so badly worn as to be unbelievable.. a quarter inch minimum missing off the top of all of em.. he he<br /><br />basially the car ran perfectly okay around town.. idled okay.. cruised okay at 80 mph or so just lost all it top end performance.. okay for normal (legal) driving lets say.. this also happend slowly over time so that i never really noticed.. only in the fact that i was sure the car used to have a lot more "extra" power than it had now kinda thing..<br /><br />when i eventually got round to rebuilding the engine due to oil burning i was amazed just how badly the cam had worn over the years.. basically u still get your full time of valve opening they just dont open as far.. course this is all permitted to happen cos of those auto adjusting hydrualic lifters.. with old fashioned solid ones any cam wear soon made itself heard.. in fact i seem to remember that replacing the oil filled lifters with solid ones was a performance upgrade at the time..<br /><br />one quick way to test for cam wear is to remove a lifter and see if the bottom is still dead flat and unworn.. as wear takes place they go concave.. also the corners wear off the cam to fit the worn concave followers.. the middle wears far more than the outside cos they spin around during use..<br /><br />as someone said earlier cams are case hardened so after the initial hard surface wears away they wear very quickly.. not super quickly thow..<br /><br />i still think that worn cams must be a very common cause of top end power drop offs.. and i would also think that wear would be over most of em not just one..<br /><br />and slight wear over a bunch of em isnt gonna show up with compression tests either.. the only way to check for cam wear is to look at the thing and the followers and measure how much cam u have left compared to a new one it to be really sure..<br /><br />trog100

 

[skyking_22]

Re: Mercruiser IO, Loss of power

Update. Finally concluded the saga. The Judge saw things my way and they just finished paying me back $6250.00 in expenses and court fees. And as if to add insult to their injury the engine they put in the boat mysteriously dropped 3 valves (imagine that, the valve clips just fell off) 2 days before the warranty ran out. Mechanical failure and they had to put in another engine. Moral of the story. Even the big boat dealers need to treat the little guys with the same treatment as the rich ones.