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Discussion in 'Newbie Lounge - NEW' started by billnpat, Dec 29, 2009.
Must have been a big rig hauling it down the road.:smt101
go back to your exclusive Man Cave.
We were happy to have a civil discussion without the Almighty Know It All interjecting.
You may disagree with my my mechanic. Lets see some documentation supporting your childish response.
No where in my manual does it says not to operate at WOT. Does Yours?
What, you find a down-hill run somewhere? LOL
I have v-drives, so I'll never catch your I/Os. :smt043
Thanks for the info. Is there some sort of documentation that states that running at
WOT is a No No? is there a time limited at WOT because of oil caposity? Is there a Merc paper on this? I would certainly like to know as not to burn up my motors.
Thanks for any info.
I guess this is a bit corn ball and not very scientific. I like to throttle the engine up as I hum the key of A and once they match....
That is where they purr hummmmmmmmmmm.:smt043
I am with ya Wayne. 40+ PSI oil pressure when ever and what ever speed. No matter how long or hard at the throttle.
Not sure why this is an issue...
Since we know how infallible Mercruiser engines are, I guess we should be thankful that there are other brands used in our Sea Ray boats.
One of the problems with forums is that generalizations can bite unsuspecting readers in the butt. I can't speak to Mercruiser's current reommendations for running at WOT but I can definitely tell you that Caterpillar, Cummins, Yanmar and MAN specifically limit the amount of time engines can be run at WOT.
For Caterpillar engines rated for pleasure craft use, the engines are limited to running no more than 8% of the time at WOT. Further, engine life is measured in total lbs of fuel burned..........run 'em at WOT and you very significantly shorten the life of the engine since engine life is consumed much sooner than if the engines are run at normal cruise speeds.
But, hey........crank 'em up and let 'em eat.
BTW, is that mechanic who recommends running at WOT also the same guy who will repair the carnage when one lets go?
I was just kidding about the humming... Thought it would get a laugh.... To serious tonight.
Thanks for the response. I am sure there are different rules of thumb for Diesel engines vs Gas. I am not an expert, and have simply stated what my mechanic says to me.
Thats what this forum should be about.. sharing info and hopefully deciding if it is valid or not. My mechanic may have his head up is A$$. Just relaying info here. I welcome other opinions.
I am happy to hear all options and opinions. Negative posters need not apply without adequate backup, just for the sake of being negative.
So, the question is and remains, what is the problem with running at WOT? Feels good on my boat, but do not want it to self implode doing so.
Any insight greatly appreciated.
I trust Frank's statement about the diesels.
In addition, I have seen in numerous Merc manuals for both small block and big block V8's, the recommendation not to run "for continuous periods above 3600rpm", and that doing so may "severely shorten engine life".
As far as the gas versus diesel debate, diesels tend to do better than gas engines when run at a higher percentage of rated rpm for extended periods.
I don't really care how anybody else chooses to run their motors. I don't have to fix them. I am just trying to point out that my comment that running motors at WOT is indeed hard on them is not simply an opinion. It is a fact. And to ease any flames or thoughts about arrogance on my part, I did not establish the fact. I (as others) just recognize it.
And Wayne, that 3600 rpm recommendation was in the Sea Ray manual that came with an '81 210 we used to run with an OMC 800. But I can tell you from experience, I'd be A LOT more worried about the OMC's than the 350's.
Oh, and I noticed a couple skeptics about Wayne's stated top speed. FWIW, 270's with twin 350's will typically get north of 50mph.
The oil is actually running cooler in a boat than a car. A car runs at around 180 to 195 a boat is running at 140 to 160. A Chevy big block is a 4 bolt main HD engine, they will break if abused. When I had my Formula my cousin always gave me crap because I always ran WOT or idle period I had that boat for 10yrs and only cracked a head when I sucked some sea weed. A Chevy small block it also has 4 bolt main and HD.
Now if you over prop it and are putting a strain on it yes you are looking for trouble and will break some thing due to it not being able to rev up and detonation in the combustion chamber, that is why there different gear ratios in lower units for different engines. Now on a diesel I am not sure about but on a gas job I say go for it as long as you can afford the gas and as long as you are propped right and you maintain it with the correct oil and filters and good gas.
I also found in the Mercruser Service Manual #9 on page 7 it states that Marine engines are subjected to prolong periods of heavy load's and WOT there for require HD components.:thumbsup:
As far as fuel injection, the injectors can get blockage just like our cars I would be putting injector cleaner in those newer boats from time to time because we all know the fuel from a marina isn't always the best and WOT will help to clean them out. Most cruisers don't run that hard mainly due to the cost of doing it and the ride isn't like a 24deg Deep Vee. I am sure I will hit the WOT until the wife starts yelling SLOW DOWN but not as much as I did in the Formula but that 50mph sure was fun.:grin:
Spookeay If you read back... I hummmmed first !!!
My "idiot" comment earlier was out of line ... and for that I apologize. A 30 yr veteran tech does deserve some professional courtesy from another like my self.
These technical threads are why I hang out at CSR. I've got to go to work now, my last day of the year. But I will definatly be back and comment on bottom end loads, oil temp and cavatational erosion on rod bearings ...Ron
I'm no expert, and not criticizing anyone, but I simply cannot imagine how long periods of WOT can equate to anything other than a shorter lifespan.
The service life of any mechanical part is finite. Subjecting everything from the circulation water pump, all the way back through to the prop, to greater stresses can only mean greater wear, right? How could it not?
It only seems logical to me. WOT may not break anything today, but that point down the road where something wears out will be reached sooner for the added stress. If nothing else, it certainly won't make anything last longer.
Right or wrong, just my opinion. :grin:
So many experts....so little time..:huh:
This is what Mercruiser says:
20-Hour Break-In Period
IMPORTANT: The first 20 hours of operation is the engine break-in period. Correct break-in is essential to obtain minimum oil consumption and maximum engine performance. During this break-in period, the following rules must be observed:
Do NOT operate below 1500 rpm for extended periods of time for the first 10 hours. Shift into gear as soon as possible after starting and advance the throttle above 1500 rpm if conditions permit safe operation.
Do NOT operate at one speed consistently for extended periods.
Do not exceed 3/4 throttle during the first 10 hours. During the next 10 hours, occasional operation at full throttle is permissible (5 minutes at a time maximum).
Avoid full throttle acceleration from IDLE speed.
Do NOT operate at full throttle until the engine reaches normal operating temperature.
Frequently check engine oil level. Add oil as needed. It is normal for oil consumption to be high during the break-in period.
After Break-In Period
To help extend the life of your Mercury MerCruiser power package, the following recommendations should be considered;
Ensure that propeller allows the engine to operate at or near the top of the specified WOT rpm range (Refer to Specifications and Maintenance) when at full throttle with a normal boat load.
Operation at 3/4 throttle setting or lower is recommended. Refrain from prolonged operation at WOT rpm.
Change the oil and oil filter. Refer to Specifications and Maintenance.
The simple answer is that exceeding 3/4 throttle on a regular basis will shorten the engines life.
The real question is why would you want to push the throttles beyond 3/4 other than testing for WOT. What usually happens is that other problems stop the owner from going "fast enough" and they keep pushing the throttles up to compensate for a dirty bottom or host of other maintenance issues. When that happens, it is only a matter of time before a more serious problem shows up.
Your welcome. After a lifetime of working on gas engines in race cars and go boats I have seen my share of destroyed engines.
In boats, most gas engines fail due to poor maintenance (ie water ingestion, no oil, bad impellers etc). I saw one last year that the owner blew both engines running at WOT and not paying attention to engine temps going through the roof. He hadn't used the boat in 3 years and got drunk and took it out with his buddies. It was a simple problem both impellers were shot and the engines superheated and locked up with a bang you could hear a mile away.
What most owners don't get is that the faster the engine turns, the less time you have to react to a potentially damaging situation. An impeller fails, a hose bursts, an oil line leaks ......at wide open throttle you have a lot less time to react. That's why race engines detenoate in such a spectacular way. "I saw it getting hot....by the time I hit the kill switch it was too late..."
:thumbsup: Thank you John....
This is perfect. The family is slowly coming back. I can not post at work, so while I was reading this stuff last night, I wanted to comment as follows:
Gary, I disagree. The mechanic is not an idiot. He's just staying in business. Heeding his words may be different.
One example of engines lasting for freakin' ever even under extremely harsh conditions does not make for a good example. You probably take great care of them and have gotten lucky with regards to manufacturing defects, which do occur, but may only rarely show up under the harshest of conditions.
" Your mechanic is an idiot. "