Mercruiser 3.0l cuts off at high revs.

[virtual120]

After

 

[fat fanny]

Re: Mercruiser 3.0l cuts off at high revs.

With this type of intermitant issue I would start by cleaning and checking all electrical contacts and leads 1st,2nd go through the entire fuel delivery system filters lines antisiphon valve fuel tank pick up and it's screen along with the fuel pump (check pressure).3rd compression check on all cylinders, 4the check timming and it's advance. All the things can be done yourself go to the stickies section @the top of this forum and download the manual for your engine and start reading for that matter read alll the good info in the stickies it will get you started for free good luck!

 

[havasuboatman]

Re: Mercruiser 3.0l cuts off at high revs.

First, how about giving us a little more detail about the engine? Year? Hours? Mechanical condition? Has it been neglected?
Second, your title says you are cutting off at high revs, but in your message you say high or low speed. Which is it?
When you say misfiring, is the engine back firing?If so, is it doing so thru the intake?
What viscosity oil are you using? ie 10/40, 20/50?
What does your oil pressure gauge read when this happens?

You could very well have sticky lifters (elevators). You could be floating your valves because your valve springs are weak or broken. Or you could have badly adjusted valves. (too tight.) You may even have burnt oil caking the stems and guides (valve) that is binding them up.
Does the boat burn oil?
Did they check for water in the fuel?

 

[virtual120]

Re: Mercruiser 3.0l cuts off at high revs.

OK, heres a few more details and thanks for the replies so far.

Engine is 1998 and very well maintained. The last owner had just spent $4,500 on it before we bought it. It ran great for two seasons until we had a service on it last year. Thats when things started to happen. Occasionally the engine would splutter at high revs but quickly recover. I have been told the guy that serviced it had put the wrong oil in it as when it was recently inspected, they said the oil was very thick and gluepy. I cannot tell you what was put back in sorry. I can find out when the garage is open again in the new year. All i know is its a lot thinner !

I say it happens at high revs as it mostly cuts off at high revs but can happen at about 2000 revs too. After about 20 minutes of driving and stopping, driving and stopping, it appears to clear itself and then is fine for the rest of the day!

We have had the engine reglarly serviced and really look after the boat. Incidentally, this first happened the first time we took it out after it was sat up over winter (outdoors).

The Oil pressure remains at about 40. Its not back firing but just suddenly runs VERY rough and we have to pull back on the throttle, wait, then after a few seconds it clears itself. It is a mechanical noise. We have had the carb cleaned and water was found in their so we fitted a fuel filter/seperator.

I have spent many hours on forums reading similar problems although its hard to find exactly the same problem. We have been unsuccessfull with mechanics so far who simply charge us for may hours of guess work which is why I feel reluctant to take it back before we have a better idea of what we need to do next.

Incidentally, since this has started, and I dont know if its coincidence, most of the guages are now faulty. The trim only reads down to 1/4, oil guage flutters when we accelerate and the fuel guage always reads full (we have fitted a new sender and it does the same thing. We are going to go through all the electrics to clean and check the contacs today.

Thanks for your help.
Tim.

 

[vegasphotoman]

Re: Mercruiser 3.0l cuts off at high revs.

Im a bit scared of any mechanic that calls the lifters "elevators" shadetree mech???????

I might Check fuel pressure should be about 6 to 8 lbs with a mechanical fuel pump. (Local auto parts stores have cheap fuel pressure check guages)

mebbe the float needle is sticking in the carb....kinda sounds like its fuel starving ...intermittent sticky carb or improper float setting, check the float setting. you would need the paperwork that came with the carb kit for the exact float setting, or one from a thread of a similar carb. (actually I might have one from when we overhauled our 3.0 carb it was a 1990 3.0 mercruiser)

you say probs started AFTER some repair guy was working on it, what did HE service?

 

[virtual120]

Re: Mercruiser 3.0l cuts off at high revs.

Im not sure its anything to do with carb . Everytime we go out its the same, we drive round gently for 15-20 minutes then its absolutely fine for the rest of the day. Tio me it would seem that the lifters are jamming up when the oil is thick but when it warms it clears and they work !!

Cheers
Tim

 

[Don S]

Re: Mercruiser 3.0l cuts off at high revs.

Is the oil black or milky colored? Is it overfull?
If over the full mark, it could become areated which will cause the lifters to collaps.
I would be calling the person that changed the oil back when the problem first started, and ask what they put in.

 

[T-Bone Coug]

Re: Mercruiser 3.0l cuts off at high revs.

Tio me it would seem that the lifters are jamming up when the oil is thick but when it warms it clears and they work !!

This sounds feasible, especially if someone used an extremely heavy oil, as per your description. While it is possible for old oil to remain in the hydraulic lifters after an oil change, it should have mixed sufficiently with the new oil after running at 2000rpm or above for a few minutes.

Drawing on my automotive experiences* I used to purge my hydraulic lifters by holding the RPMs at 2.5k for 30sec, then drop to idle for 30sec. It took 5 cycles to purge the air out of the lifters on a car that my friend drove with a very low oil level for several days. Got rid of the lifter noise he had been having.

I'm guessing your oil is still not proper if it takes 20 minutes to heat up to operating temp, after nearly a whole season. Check your oil when it is cold to see how thick it is. If it is thick like honey I would suggest an engine oil treatment (solvent-type flush), running the boat at operating temp for at least 30 minutes, followed by an oil change to the properly rated oil and new filter. If the oil is NOT thick like honey, I would remove the lifters and flush them with solvent before reinstalling them.

Good Luck

*Automotive engine experience is often not equivalent to marine engine experience and should be carefully scrutinized prior to application of information supplied!!

 

[virtual120]

Re: Mercruiser 3.0l cuts off at high revs.

Is the oil black or milky colored? Is it overfull?
If over the full mark, it could become areated which will cause the lifters to collaps.
I would be calling the person that changed the oil back when the problem first started, and ask what they put in.

Given that the engine is Ok after about 20 minutes, could this still be the case that the lifters are collapsed ? Wouldnt it not be permanent if that was the case - I dont know !

Thaks
Tim

 

[virtual120]

Re: Mercruiser 3.0l cuts off at high revs.

I would suggest an engine oil treatment (solvent-type flush), running the boat at operating temp for at least 30 minutes, followed by an oil change to the properly rated oil and new filter. If the oil is NOT thick like honey, I would remove the lifters and flush them with solvent before reinstalling them.

We have done exactly this and the problem remains after a further 4 hours of boat use. I am thinking the lifters need taking out and cleaning. This is what the mechanic suggested. Is it something we could do ourselves. Is there any danger we could balls something up ?

Thanks for the reply.

Tim

 

[Don S]

Re: Mercruiser 3.0l cuts off at high revs.

Incidentally, since this has started, and I dont know if its coincidence, most of the guages are now faulty. The trim only reads down to 1/4, oil guage flutters when we accelerate and the fuel guage always reads full (we have fitted a new sender and it does the same thing. We are going to go through all the electrics to clean and check the contacs today.

The above statement makes me wonder about a couple of other things.

Before you take it all apart, have you actually checked the battery cables to make sure they are in good shape, clean, and TIGHT. Both positive and negative cables and both ends. Also make sure the main harness connection is clean and put together correctly.

Do you have an engine serial number handy ?

 

[Alpheus]

Re: Mercruiser 3.0l cuts off at high revs.

Just put new lifters in. They are around 5 dollars a piece for standard lifter and around 13 dollars for roller...

 

[virtual120]

Re: Mercruiser 3.0l cuts off at high revs.

The above statement makes me wonder about a couple of other things.

Before you take it all apart, have you actually checked the battery cables to make sure they are in good shape, clean, and TIGHT. Both positive and negative cables and both ends. Also make sure the main harness connection is clean and put together correctly.

Do you have an engine serial number handy ?

Ill get the engine number later today. We have put two new connectors on the battery end. Havnt checked the main harness - dont know what that is but I guess it goes into the fuse box ?

Thanks
Tim

 

[virtual120]

Re: Mercruiser 3.0l cuts off at high revs.

Just put new lifters in. They are around 5 dollars a piece for standard lifter and around 13 dollars for roller...

The mechanic that was working on it told me they were $150-$200 for a set (New Zealand Dollars). I dont like the sound of this.

Tim

 

[Don S]

Re: Mercruiser 3.0l cuts off at high revs.

I don't think your problem is the lifters. Without nothing more than thick oil to go on, I sure wouldn't be replacing lifters without some further testing.
Are you getting any backfireing? Or just lifter rattling ????? And how sure are you it was lifters and not pinging from preignition.

 

[EddiePetty]

Re: Mercruiser 3.0l cuts off at high revs.

.......Incidentally, since this has started, and I dont know if its coincidence, most of the guages are now faulty. The trim only reads down to 1/4, oil guage flutters when we accelerate and the fuel guage always reads full (we have fitted a new sender and it does the same thing. We are going to go through all the electrics to clean and check the contacs today.

Thanks for your help.
Tim.

...kinda sounds like you are losing power feed from the ignition switch and/or laynard (if fitted) via a faulty connection. This would also account for engine mis-fire and ill-running.
I believe a complete walk-thru of electrical connections , beginning at the batteries, through the helm and ending back at the engine ground is in order. And I don't mean just mechanically tight connections either!!! Please check each connection with a volt/ohm meter.
FWIW....Ed in 'ol Virginny

 

[virtual120]

Re: Mercruiser 3.0l cuts off at high revs.

I don't think your problem is the lifters. Without nothing more than thick oil to go on, I sure wouldn't be replacing lifters without some further testing.
Are you getting any backfireing? Or just lifter rattling ????? And how sure are you it was lifters and not pinging from preignition.

Its not just lfter noise though. We completely loose power and the engine rattles and clonks then dies to a very poor idle, then recovers quickly then we are off. After 20 odd minutes of this, the boat is then fine for the rest of the day without issue.

 

[virtual120]

Re: Mercruiser 3.0l cuts off at high revs.

I don't think your problem is the lifters. Without nothing more than thick oil to go on, I sure wouldn't be replacing lifters without some further testing.
Are you getting any backfireing? Or just lifter rattling ????? And how sure are you it was lifters and not pinging from preignition.

No backfiring at all, engine only dies after about 20 seconds of hard throttle. After its done this for about 20 minutes or so, everything is fine.

 

[Don S]

Re: Mercruiser 3.0l cuts off at high revs.

After you check all the electrical connections, Get a clean outboard gas tank, make sure it's clean inside, use new clean fuel and hook it directly to the engines fuel pump and see if it cures the problem.
I still think it's electrical, just want to isolate things.

 

[Alpheus]

Re: Mercruiser 3.0l cuts off at high revs.

Could be a fuel issue. When it sits for awhile sediment at the bottom of your tank contaminates the tank filter and once the fuel gets sloshed around it breaks up the sediment and runs fine. I would definitely try the remote tank option to confirm your problem or rule it out...