350 Mpi Losing Oil

[QC]

Re: 350 Mpi Losing Oil

Guys, we don't even know if this boat will maintain a plane below 3500 RPM . . . With boats, fuel efficiency has very little to do with the RPM and engine efficiency, it is much more about the hull efficiency . . . The fact that many boats seem to get better efficiency between 3000 and 3500 RPM is because they also top out around 45 - 55 MPH, so the "sweet spot" just happens to be down there where an efficient plane of say 25 - 35 MPH is . . .

Also, current automotive engines are often cruised at less than 2000 RPM so that they are "lugging" more. This is on purpose, not because of stupidity. Don't confuse marine and automotive efficiency. They do not relate well . . .

 

[SEA SALT]

Re: 350 Mpi Losing Oil

Hi Guys. Sorry, had to step out for a little while.

Really appreciate everyone's very helpfull comments and even the criticism is welcomed..let's face it, when one does something stupid there is no denying it and all that's left to do is to learn from the experience.

It was a long trip and I am sure I did not plan it as well as I could have. I have owned a 22' Grady White seafarer for 3 years and we take lots of trips 8 to 10 miles out to sea, with an ocasional 30 mile trip to go deep sea fishing. My Seafarer has a Johnson 225 HP Ocean Runner and it has been a great experience.

We did load up on tools and safety stuff. The boat has a Raymarine C80 and all kinds of safety stuff, including 4 extinguishers, emergency raft, VHF radio, etc, etc. The engines had full oil charges as the dipsticks showed but once we left Brownsville, we really hit the wilderness. We loaded the tanks full of gas and placed a couple 55 gallon drums with fuel in the back seats (lounge)so we could re-load along the way as there was no where one could do so for a very long ways.

Full tanks gave us a range of 4 hours run time. It was a beutifull trip, we hit a bit of wind coming out of Brownsville (a few 16' waves leaving the coast) and hit another storm along the way but otherwise pretty fun.

I was unsure of the appropriate oil pressure so I kept monitoring the temp gauges which were also a good indicator in case the raw water intakes got fowled somehow. On the 350 MPIs the smart craft system works great and cuts out the engine to prevent damage in case of a major failure like lack of oil. I got to say these systems are great.

Finally, I tend to agree with everyone in that the engines simply burned the oil and I just trusted too much that inboard engines would not burn oil like the did in the end. I was also kind of hard to lift the engine compartment's hatch with the two 55 gal drums on top, but that is another mistake I learned from this experience. And ofcourse no excuse.

I do keep relays, belts, tools and a 5 gal oil jug on the boat at all times.

I will keep a log, and have the compression checked just to keep myself out of trouble.

As I said, thanks for all the great advice and I will be a regular now.

Best Regards,

SEA SALT

 

[SEA SALT]

Re: 350 Mpi Losing Oil

Hi QC.
On my boat, we need to be at around 3200 RPM to get it to plane and that is using the hydraulic trim tabs. I think 3500 to 3800 is optimum but I have still to get to know the boat well enough. I am starting to keep a log on fuel consumtion, etc so it will be some time before I know for sure.

Thanks again.

 

[QC]

Re: 350 Mpi Losing Oil

That seems to be a high RPM just to get on plane and keep it there. Once you reach plane can you back the throttle down to say 3000 - 3200 RPM and stay on plane?

Quit freaking this guy out . . . this is a 32 footer . . . Frankly, these could be 4.3's for all we know although I seriously doubt it. It is not about RPM it is about horsepower. This boat needs 3200 RPM to plane because there is not enough horsepower to do it below that. Jeez, there are 20 footers with 5.0 220s that need 3200 RPM to plane . . . My boat planes at 2200 RPM. So what?

 

[HT32BSX115]

Re: 350 Mpi Losing Oil

I do keep relays, belts, tools and a 5 gal oil jug on the boat at all times.

Good.

I think you lucked out and the Smart Craft system pretty much saved your bacon!

Your best bet now would probably be to just run it and monitor the oil (and probably fuel consumption) to get a feel for what the the oil burn rate is.

They may have been low to begin with and just burned a couple of qts in 10-20 hrs or so.

It's very possible that whomever changed the oil before you got it didn't put enough in or didn't have it level and checked it wrong.

 

[QC]

Re: 350 Mpi Losing Oil

Sorry if I came on strong Bubba, but this is a big flippin' boat. I personally think his cruise RPM is about right. I missed the 350 comment, but my point was that if he needs 3200 to plane the boat then 3800 is probably a good cruise RPM, maybe even 4K . . . If we tell him that 3200 seems high, then the next thing will be "what's wrong?" when everything is probably very right. The only solutions to high planing RPM are trim (I think he gets that), trim tabs (already mentioned) or higher pitched props (which would make this entire situation worse) . . .

I believe this is a simple case of horsepower required vs. horsepower available. Oh, and I do see 350 MPI's now which have a WOT range of 4800 - 5200 . . .

 

[Bondo]

Re: 350 Mpi Losing Oil

Sorry if I came on strong Bubba,

Ayuh,...

Amazing how that happens when somebody gets that word Moderator pasted beside their name,....

 

[QC]

Re: 350 Mpi Losing Oil

Actually makes me ***** foot around more, I forgot how bitchen I was and got carried away. What's your excuse?

Yes, I am a CA boy who uses regionally specific slang like bitchen, I find the word, like, totally bitchen, so I use it a lot . . . to describe a bunch of bitchen stuff . . .

 

[QC]

Re: 350 Mpi Losing Oil

Ding, ding, ding. And Bubba has said the Magic Word . . . Torque, and for that you get a 4,000 word essay from none other than QC . . .

Well to cut this short, the FACT is, and I bold and yell that on purpose . . . The fact is that peak torque is ONLY in play when the throttles are 100% mashed (read 100% open). Period, end of story. This a fact, unless the engine has a full speed governor (isochronous) and the throttles will mash themselves. Somewhat common on diesels, but not 100%, I have never seen one on a gasoline marine engine with the exception that you could call Auto Pilot, isochronous, i.e. the throttles will mash themselves . . .

So imagine this, you mash your throttle(s) to put her on plane (any boat) and then she comes over onto an efficient plane, and then what begins to happen if you leave the throttle(s) there? She gains speed until she reaches WOT RPM and max speed (assuming she is propped correctly). Buuuuuuut, you don't wanna go max speed, so you back OFF the throttles to bring her down to cruise. In this case 3800 RPM. As soon as the throttles are nudged back even a smidgen, peak torque for any given RPM is out of play. The fact that peak torque is developed at 3,279 RPM or 3,922 RPM is meaningless as far as Marine cruise RPM is concerned.

The reason that it matters to a car, or truck, is that if you maintain speed above peak torque it gives the best drivability for negotiating grades without shifting . . . No hills in a marine application, no gears to shift, so relating the two is VERY difficult. Yes, I understand swells, which takes me back to the governor, annnnnnd, if you had one, higher RPM would give you a better chance at negotiating big swells without falling off of plane.

I said "short" but I can't help myself, it is a disease, and I've got it bad when it comes to torque. Most misunderstood engine spec there is.

 

[SEA SALT]

Re: 350 Mpi Losing Oil

Hey Guys.

Very interesting discussion regarding RPMs, Torque, planing speed, etc. I will run the boat soon and get back to you guys with all the details aftor I log them.

I did see some smoke when staring the engines and while running we got some blowback that smelled like gas mixed with oil.

I cheked with my mechanic and he says I don't have oil coolers on these engines which might be a great idea for extended runs.

On the engines, I agree that the smartcraft system saved my bacon. The engines show about 55 PSI oil pressure when running at 3800 RPM which is a good sign.

Any way, I will be back with more information.

Thanks,

SEA SALT

 

[QC]

Re: 350 Mpi Losing Oil

running a 350 under full load at 3800 RPM.

Whether it is a 20 footer or the Titanic, if the engine reaches recommended WOT RPM, then the "load" at 3800 is the same and not "full", high, but not "full". Prop "curves" are almost perfectly linear. So the fact that I "cruise" my 23 footer, 6.2 MPI often at 4000 RPM is even worse . . . the load is high, the horsepower required is high, but that's what I (we) paid for . . . There is no question that our gasoline marine engines work harder than an automotive application . . . That's why they're often only good for 1000 hours, which to equate to 100,000 miles you'd have to run an avergae 100 MPH in your car/truck . . . If you say, "well I get 150,000 miles", then OK, say it's like averaging 150 MPH . . . Yes, high load, and yes they use more oil at high load factors, but again, 'sawlright.

BTW, I think the "smell" and smoke was unburnt fuel, not oil. No O2 sensor, you're gonna have some unburnt fuel sometimes, even with EFI. If you are seeing blue smoke, then that is another discussion. Any consistent, visible "smoke" (not steam) with a gasoline engine is baaaad . . .

 

[CheapboatKev]

Re: 350 Mpi Losing Oil

SeaSalt,
First and foremost WELCOME ABOARD!!
I must say you have taken your floggings on here and have held your character!

I'm glad you made it back to port from your adventure! I guess nobody smoked a cigar near those fuel drums! (whose weight may or may not tie into the whole rpm-plane-tourqe but lets not get that started again issue!) lol

 

[SEA SALT]

Re: 350 Mpi Losing Oil

Thanks CheapboatKev.

I appreciate the comments. Of course we knew we had us a floating bomb so no one smoked at all. And let me tell you, re-fuelling on the high seas is not all that fun, specially when we had to do it during a squall.

In our 700 mile trip we stopped 3 times to re-fuel. Not because we wanted to do it that way but because there was no where else to do so.

Don't think I will be doing too many of these kind of trips but it was a great opportunity to get to know the boat better and to live through a great experience. As I keep reading the many opinions and comments, I will be learning more and more how to be a better boater.

I would say though that there should always be a balance between knowing what is the best for your boat/engines and having some fun, which at the end of the day is what is all about for me. So while there are times when all I want to do is cruise at 1500 RPMs down a waterway, there are also times when I want to go at WOT and times when the size and frequency of the swells determine the best speed to run the boat at...think everyone would agree that it is a great feeling to be on the open sea with glassy waters at WOT...right?

On the maintenance issue, I will have my mechanic to check the compression on the engines and the only reason I had not done so was that they show such good oil pressure on the gauges. None the less, I think that is a good idea and will have it done.

As far as oil changes, using the 1,000 boat hours to 100,000 car mile analogy, I would think that if I change the oil in my car every 3,000 miles, then I should change the oil on my boat every 35 hours or so...what do you guys think?

Thanks,

SEA SALT

 

[QC]

Re: 350 Mpi Losing Oil

When I say full load I meant its at full load for that RPM.

No . . . It is NOT at full load for that RPM, the ONLY time it is at "full load" for ANY RPM is with the throttles 100% mashed . . . . Maybe, I am not making myself clear, (nothing unusual there accourding to the wife. )

Take a look at these charts, they are for a diesel, but the concept is the same. Any thing above the prop load curve (the relatively straight lines) is "reserve" power. The three graphs are, power, torque and fuel, top to bottom.

If you back out of the throttles, or let her settle at any speed, all follow the prop curve. If you mash them they (all three) jump to the peak curves, but they only stay there until the match between horsepower available, and horsepower required are reached . . . which is . . . the prop load curve. Engineers use the torque curves to make sure you don't break stuff like input shafts and propshafts, but ultimately all you care about are the horsepower and fuel curves . . . the two things that cost money . . . and this is why Marine manufacturers rarely advertise torque numbers, they are relatively meaningless. The marketing guys talk about it all the time, because the public responds to it . . .

 

[HT32BSX115]

Re: 350 Mpi Losing Oil

When your Mech does that "compression" check it might be a good idea to suggest a "leak-down" instead of a regular check to help determine where the "leak-down" actually is. (rings?)

Mercury suggests 100hrs between oil changes on most of the engines. That's not a bad thing at all if you're running the engine a lot regularly. If it doesn't run much then you might want to change more often. once every 6months or year etc..

I think you did say that you had 25W-40 oil for it, or that it was changed with 25W40........

but if someone put 10W30 or 5W30 (syn etc) it may have higher oil consumption due to that. Also if the fuel injection was dumping excessive fuel into the engine it might dilute the oil but it's pretty unlikely that both engines have the same exact problem.

If you didn't change the oil yourself, it could be possible that someone put 5W/10W-30 etc in both engines. (and didn't get them full "to boot"!!)

Once you determine that nothing is wrong with the engines (hope hope hope!) and change with known type/amounts of oil, you'll determine exactly what your burn rate is.



Cheers,


Rick

 

[q5ka]

Re: 350 Mpi Losing Oil

Many change oil at 100 hours or once a year for those of us up north. Some also change a bit more frequently depending on how rough you are with equipment. Every 35 hours might be much but then again, your service/owners manual would be able to tell you more.

 

[QC]

Re: 350 Mpi Losing Oil

I thihk we are describing the same Elephant, but I have its trunk and you have its leg.

Does anybody have an emoticon showing an Elephant trumpeting while also stomping on a bloodied and dead horse?

 

[Bondo]

Re: 350 Mpi Losing Oil

Ayuh,....

No Doubt the same Bull Elephant,....

But,...
I'm not so certain that Either of you have a grip on his Trunk, or any of his 4 legs.......

 

[SEA SALT]

Re: 350 Mpi Losing Oil

Thanks for all the good recommendations guys.

Will check the oil constantly and change it every (probably) 60 to 80 hours...oil changes are cheap, engines are not. Guess this whole thing shook me up pretty good and don't ever want to go through it again.

I did put in 25W-40 when adding oil as that was Mercruiser's recommendation but don't know what the other guys had in there before.

As I said, weather permitting, I will check all my numbers and get back to you all.

Thanks

SEA SALT

 

[QC]

Re: 350 Mpi Losing Oil

I absolutely have a grip on the dead horse's leg . . . not much else, but he's not getting away I can promise you that.