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raybo3

On my 342 with the 5.7 mag's my "sweet" spot is abuut 3700 rpm and its close to 30 mph. I would say at 3600 your about where you should be. IMO

Michael T

Hey Seguir, don't be tough on yourself, we all learn continuously about boating!. If your boat hull is right up on top of the water you are on plane. You can feel it - the boat feels "free" and just zips along the surface. If not then you are running displacement or partial displacement. IF your boat was only partly on plane with a big load and turning 3600 rpm then I see where the gas and oil went. I would recommend absolutely making sure whether or not you are on plane in the circumstances you mentioned, because IF you were turning 3600 rpm on displacement cruising with a heavy load - then it would be my opinion that your engine was being massively "lugged" and that would account for the oil burning and gas use for sure. P.S. IF you were running displacement at 3600rpm and in the future you make sure you are on plane at 3600 rpm your oil and gas burns should be normal. One more question - some of the guys on the list have had prop sets that have too high a pitch on them (right from the dealer) causing their engines to fall too low in the wide open throttle range for their boat. How confident are you that you have the correctly pitched props?  Sorry to ask so many questions but there has to be a logical explanation for this! MT 

seguir

Thanks Michael and Mark.

Now my questions are:

Could I have caused any damage?

and Second:

Is it ok to run at lets say 4000 RPM if that is what it takes to keep it on plane?

 

Michael T

Hey Seguir, if  your engine was run at displacement at 3600 rpm a few times my opinion is that no lasting damage occured. From now on - if you have a big load and run at 4000 rpms it's my opinion that your engine will be fine - as long as you are ON plane! I would keep an eye on the colour of my oil and maybe change it and the filter a bit more frequantly if I found myself running at 4000 rpm a lot. My 2 cents. Again if you think your boat won't hold plane with a "reasonable" load something - like prop pitch - might be wrong. MT

seguir

Thanks Michael.   I am going out tonight with my wife to see what it takes to bring it to plane with only the two of us and no heavy load.  I have done 40 hours on this oil change and will change it tomorrow just to be sure and will monitor the oil level.

seguir

Went out tonight, rough water.  With two people no extra weight.  On plane at 4000 doing 22 mph or 36 km.  Will try again when not as rough.   But if felt good.   I know when it is just my wife and I, I can run it at 3600 - 3800.   Ran for 45 minutes no oil burn.

Michael T

Seguir, good, that sounds right! You can even run 4200 for decent periods of time, no problems as long as you're on plane and keep an eye on the oil, in my opinion. Fingers crossed! MT

MarkB

I can't see running at displacement causing damage to the engine. It is just a load that can burn oil. Anyhow the way to find out is to run the boat at plane for extended periods and keep checking oil consumption. Getting 22 mph at 4000 rpm is a little low but it could have easily been the wind and waves.

Michael T

Mark, running at displacement will not cause damage to an engine - depending on the rpms. It's all in how the engine is run. I run on displacement a fair amount of the time. However, in my opinion, running a single engine at 3600 rpm with a loaded boat at half displacement half on plane will damage the engine by lugging it. MT

212rowboat

Seguir, hopefully removing and shaking the pcv resolved your issue.. and ir was that simple.. 

at some point an overworked engine exceeds the capacity of its flow to cool it... there is a formula really smart people use while discussing volumetric flow, where velocity of flow reaches a point where the passing volume of fluid does not exchange heat... you'd be hard pressed to exceed that sorcery with a healthy cooling system, especially with a rev limiter programmed into the tuning... its at or near that point where oil begins to lose lubricity and hang around hard parts long enough to fry out of this dimension and into  the next... 

during these same periods of over working, there is almost zero vacuum from the intake manifold to siphon oil via the pcv.. 

oil doesn not have an ability to enter the combustion process unless it slips past guides or rings, no matter how hard an engine is ran, unless it is an unhealthy engine in some regard.  

lugging an engine is terrible for it, but these things are designed for it by using stronger construction, which is to say it will survive runs north of 4k for prolonged periods better than a standard automotive build.. the blocks themselves are stronger.. valve events due to camshaft timing support this behavior.. spark ignition supports it too.. it is designed to survive in an environment such as you put it through, but all that said: it was not designed to guzzle a fifth of oil and be expected 'fit for duty' in the a.m. no more than we would be.. 

gas engines are not designed to burn oil no matter the range, and these engines have safe guards present to keep the operational at ranges you ran.... 

if you didnt shake a sticky pcv loose, and solve your issue, you still have somethingnnot right at all with your engine. 

seguir

Thanks for your comments and help.

212rowboat

a vacuum gauge is almost as handy as a code scanner/ PCM interface... you can pick one up from a parts store for very little investment.. It's a dang good thing to have in your kit..

check this link out, and about halfway down the page is a little animated gadget with different scenarios to show you how it can help you track stuff down..

given the diameter of your engines bore, and the surface each cylinder covers, you ~could~, in an extreme circumstance, burn oil to the degree you did, but I just can't buy it as that alone.. this is just my opinion, though.. maybe the tolerances of these things allow for such, as some engines built for spray or boost are loose enough to do so..

seguir

I think this is good news story for me.   Changed the oil and put on another 15 hours on the boat running mostly between 4000 - 4400 rpm on plane,  checking the oil regularly and no oil burn at all.  Season now almost completed and pulling the boat in the next couple of weeks.  I am going to have the engine checked out during winterization process.

Capt Ron

I would make sure this oil issue continues to be a dealer issue not yours. It sounds as if the engine was pounded from the first day. People who don't break in the engines properly can screw them up for life.This is the main reason I always buy new and break in the engines properly... none of my 350 Mags ever burnt a drop of oil after break in, the same goes for my 5.0L engines as well. Make sure your dealer stays responsible for the boat, it sounds as if he is brushing you off by saying oil consumption is normal...it's not.

212rowboat

that's great info, Al, and from guys who have the resources and luxury of sitting engines side by side in duplicate circumstances, with a control and multiple 'experiments'... a proper way of doing it.. I'd like to read more about that..

CaptRon, I agree about proper break in.. the hatches on cylinder walls are purposely put there as an abrasive- a slight abrasive, but one all the same.. their purpose is to marry the mating surface of the cylinder walls and the ring(s), and to somewhat direct the sweep of the rings... those rings will 'float' around the piston body until they 'seat'.. generally, they seat within 25~40hours of engine operation.. once they seat they won't move, and it is their 'final resting place', so to speak- UNLESS the cylinder gets stupid hot or gains silly pressures, which will unseat them.. massive oil consumption happens when they 'unseat', and even more can happen if they unseat in a manner that allows gaps to align... this happens both because the compression ring isn't squeegee'ing the walls, and the oil control ring is either overwhelmed or faulty, or/and, the compression ring is allowing too much crank case pressure and pushing oil directly into the intake via the positive crankcase ventilation valve.

I don't mind buying a used engine- but a requirement before I pull the trigger is a leak down test both wet and dry- not only a compression test but a leak down which allows you to determine the condition of valve seats and/or rings. If the engine leaks too quickly, one of those two items is not doing so well, and either will require a boat load of money to correct, no pun intended.  A really fast leak on a dry engine speaks of rings, a slow speaks of valve seats.. a fast leak on a wet engine speaks of valve seats, a slow could be either.

Michael T

Seguir. I'm gad to hear that you feel you have solved the issue. Question - why are you running your EC 280 at 4400rpm? Are you trying to get somewhere for a deadline, just having fun....? At 4400 rpm with a 5.7 in a 280 you must be burning through some serious gas? Just interested. MT

seguir

Michael T. I start off at about 4800 to bring it up on plane.  Once there,  I drop it to 4200 - 4400, then depending of water conditions I can keep it on plane at 4000 doing 20 to 21 mph with 3 people on board.   Anything lower then 4000 rpm I begin to lose plane.   This may be a prop issue or the outdrive may not be set in the correct position.  Both will need to be checked when the boat come out later this month.   I also need to request guests not to sit in the back till I am on plane.

Michael T

Seguir, I read back through all your posts on this and couldn't find out your drive type? What do you have - Alpha or Bravo 1, 2 or 3? MT

seguir

Bravo 3 MT

TikiHut2

Like MT I'm wondering about that speed/rpm.

21mph sounds exceptionally slow for 4000rpm. Our porky '04 270 5.7 merc mpi B3 (nearly identical in size/power to your 280) cruises like a sweetheart at 26mph running 3800rpm at 1.8gph with flow meter networked to my Garmin chartplotter (ideal trim w/avg load and calm seas). Hey, mine's certainly a thick-n-thirsty lil RV but yours must be a very thirsty ride.

In the very rare event that we run 4000-4100rpm it pushes us to 29-30mph @1.2mpg. We also start to fall off of plane when we get down to 22mph but that's at 3100rpm. I'll only run 90oct rec fuel(E0) and have a 2:20 B3 drive propped w/stock props at 22p.

Maybe your gauges are off (Faria anybody?) or your speedo tube is impaired. Are you getting your speeds from a chartplotter/gps? Can't say how to confirm your rpm w/o something like smartcraft gauges or an external tach.

Gotta go with Drew on that compression check and hope it's just odd gauge readings for speed/rpm or horrible trim adjustments. Mike

MarkB

Seguir - what prop do you have on that drive?

From my stats, you should maintain plane at around 3500 rpm, and 21 mph.

At 4000 rpm you should be doing 30 mph.

seguir

The GPS is telling me my speed, RPM is from my Gauge,   I am unsure the size of my prop. It came from the factory with the prop and I have been told it was not replaced.  When I get it out of the water I can then have a look at.   At 3500 I am not on plane, that is where I got into trouble with the oil burn.

212rowboat

can you see your exhaust? if so, what color is it?

seguir

I have never really looked at the exhaust....what are you thinking.  This weekend I should be out on the boat again....what am I looking for?

212rowboat

After reading everything again, and assuming the bottom is clear, and prop is OE, I'm thinking you're running pig rich.. pig rich is dark and stanky like fuel.. it explains engine struggling as well as fuel consumption (though rpms alone could account for that).. also lugging which promotes oil consumption.. another tell-tale is cooler running temperatures... Rich runs cooler by likely 10%...

Seeing your engine isn't sensor sniffed at the exhaust, and is table drafted variables via formula logic, the variables are:

Fuel pressure
Air density (temperature) at intake/induction
EITHER Mass air flow (maf) OR manifold absolute pressure (map),
Engine temperature sensor/sender.

I'm thinking of the ones that would trip a code most certainly, and the ones that have a pretty high tolerance or wide parameter to work within, and which ones are likely to flake out without setting a code, or to the chagrin of the pcm (which doesn't have redundant monitoring or other ways to reconcile a bad reading from a sensor)...

For this reason, I've landed on MAF or MAP sensor... It needs to be cleaned very well with contact cleaner or throttle body cleaner...

Al, which one does his have?

212rowboat

I'm ruling, on paper anyway (like all of this) air obstruction out.. if it couldn't breathe, it couldn't rev.. it could rev with too much fuel, albeit slower than proper or lean, but the power wouldn't be there and it would be more difficult for it to balance out with the air being limited (butterfly via throttle cable) at a steady rpm, which would cause it to lug...

Heavy on the fuel is harder to pre-detonate, which is why its used in choke situations almost as much as it is to more assuredly fire when spark hits it.. wet doesn't burn at all, vapors burn.. its said stoich 14.7:1 is best overall.. 15.1:1 for economy (trade is less timing advance because threat of predet), and 13.9 to 14.3 for power, depending on spark advance used..

Other things to consider: the fuel regulator isn't monitored.. it could be failing... Get a reading at the rail to check it.. injector could be hung.. unlikely you'd not notice that, though.. temperature probe is failing, giving improper readings to pcm and not allowing closed loop to take place, keeping you rich <- a circumstance like that would go unnoticed by the pcm, it would just keep plugging along thinking its warming up..

Michael T

Hey Seguir, I've been around long enough to know that there is often a simple explanation for seemingly complex matters. I wonder if we have all been overthinking your problem. So let's simplify the discussion. You have a 28 foot boat that weighs 8K (about 4 tons). You have a  5.7 L engine and B 3 drive. Maybe your engine is running within its specifications and doing all that it can to move your boat.. Your 280 is a lot of boat for a 5.7 liter handle. Load your boat with gas, water, goods and people and that 5.7 liter will really have to work. If I understood one of your previous answers correctly your engine isn't even a 350 mag. So, running your "standard" 5.7 liter at 4200 rpm to keep your  280 on plane is probably normal given what your engine is able to do. I made some calls. There is a Rinker 280 for sale at our marina with a 6.2 in it. A 6.2 liter is a stroked 350 (377 cubic inches). That 377 is an entirely different engine than your 5.7. It has a very different and stronger power curve because of its construction. I have asked a tech I know to contact the owner to see what rpms he needed to stay on plane. The tech thinks it would require close to 4000 even with a 6.2. As he said - that 280 is a lot of boat to move with a single engine, particularly a 5.7. I called a Rinker salesman I know and he said he would never have brought in a 280 that didn't have at least a 6.2 in it. I know the dealer only puts 8.2 mags in the Rinker 290s they order and that's (as far as I know) basically the same boat as your 280. Here's another example of what I am getting at. A guy who had a slip beside me at my marina had a Rinker 350. It had twin 6.2s in it. He said he had made a big mistake. He had to run his engines at 4200 rpm just to keep his boat on plane and even more if fully loaded. He said he should have bought it with the 8.1s (496 mags) that were offered at the time. He would have burned less gas and not have to listen to "screaming engines". I'll let you know what the owner of the 280 says if he gets back to my tech. In the meantime you may have an engine that is operating normally and within its specs but is just has to work hard to move your boat. I don't think it is improperly propped and switching to a lower pitch would probably put you at your redline all the time which is probably worse than running it at 4200 or so. If I am correct I wouldn't worry, if I were you. I would just change the oil and filter more frequently and use synthetic oil and let her rip at 4200! My opinion for what it may be worth. MT  P.S.

seguir

Ok, this is a lot of education and info here....but the best thing of all is that with all this info I am now able to question some of these items with the mechanic and not let the dealer here tell me everything is normal.....Thanks folks. 

212rowboat

In light of the reverend MT's testimony, I withdraw my suggestions... His argument is sound.

seguir

 Hi Michael, My understanding is that I have a 5.7 350mag that gives me 300 hp.  Before I bought the boat I question the dealer if the engine should not be at least 6.2.  He told me that it only gives me another 20 hp and would not make a difference since I have the trim tabs.  This is my first EC and now I know better.  There is a Rinker 280 with the 8.2 at the club and he has no problems.  Your opinion makes a lot of sense about frequent oil changes, but being on the safe side I think I will have a few of these items checked out.   I am feeling a bit better and can live with the restriction I have.  It is also worth while to mention that when Rinker built the 290 EC they reduced the gas tank from 100 to 80 gals.   Go figure.