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Discussion in 'Newbie Lounge - NEW' started by billnpat, Dec 29, 2009.
Oil Temp: what heats the oil up most is the load at the rod bearing and the cam slippers/lifters (newer engines now have roller lifters = less friction = less heat).
Cavitational Erosion: When the engines rod/piston group changes direction, heads down on an intake stroke, the load is shifted to the lower rod bearing. A small void is created where an implosion accures. This implosion area is where a lot more heat is created. When the combined heat from all operating parameters exceeds the bearings soft layer babit materials critical temperature, a small piece of bearing will be blown out and become embedded as the crank journal simply presses it back into the bearing somewhere else. The more movement between rod bearing and journal, the more of this type of wear acures. Heavy rod/piston groups, high rpms, thin viscosity oils and hot oil are all contributors.
An engine built to run at rated will turn at a much lower rpm than what its capable of. ie: Diesel gen set, 6 cyl, 4.25” bore, 40 qt oil capacity, 1800 rpm 24/7 … Gasoline gen set on some of your boats, large capacity of oil for its actual ci displacement, rpms most likely 3600 24/7 no problems.
I get most all this information from my career at Caterpillar. For 10 years, every day, all day, all I did was repair failed medium duty diesels and rerate others. The last ten I been doing the same with transmitions and hydraulic systems. Boats are new to me but the basic engine principles are same.
I don’t know the sweet spot on a sb Chevy as far as 24/7 rpm but I don’t believe it can be in the upper 4k range.
Not to single any one out: IMHO… I think Wayne’s World should throttle the girls back some so he don’t pound out his hull too. Just because the girls hold 40 psi oil pressure only means the oil pump is still overcoming internal leakage at a 40 psi rate.
Was glad to see some others found some lower recommended rpms by merc. This must be the cruising rpms. Was a short work day for me. cheers to all … Ron
As with most things in life, moderation is the key.
Great post and from John as well. Thanks for taking the time to spell it out.
Like a doctor, having second opinions on this forum is a great resource. While my mechanic is no way an idiot, IMO, he may have just not mentioned the fact that WOT would shorten engine life. He did say I could run it all day at WOT without problems which I assumed was overheating, etc.
I also wonder if our engines are intentionally governed somehow to prevent over speeding. Because of the tremendous load of a boat over speeding may not even be possible unless propped wrong as mention by others. Never seen a cruising type boat with a tach that has a red line indicator like a car does.
I couldn't find the 51.9mph pic yet. :smt021. I'm still looking threw the 3000 plus pics i have. . Here's one that i took with 10 people & 5 coolers filled with beer on board going to the beach at WOT. :thumbsup:. .
I have them on my girls also.:smt001
No expert here either, but for those that think running continuously @ WOT is fine, I suggest you jump in your car, limit it to 1st gear and drive around @ red line for a few hours. Same thing. Do you expect this won't affect engine/vehicle life?
Gary, as an observer your pragmatic humor is much appreciated. It's great to have someone that will say what most others are thinking, although I am sure I might feel differently/defensively if I was the receiver.
Damn Wayne, were you thinkin someone else was going to get your favorite spot? :grin:
You're just talking silly with that statement :smt101. Do you see truck motor sh*ting to bed ??. Today i went and got 24 tons of road salt for a friend. I ran that Mack motor at 2150rpm's for 7hrs and it didn't come unclued. Heres the deal. If its going to break its going break. If not you're GOOD. :thumbsup:. PS. I drove truck for 33yrs and have over 1 1/2 million miles under my belt :smt001. I never blew a motor running like that. :smt038
I find it amazing how many people that just don't grasp that concept! :smt038
What is WOT for the engine? Did I read it right that you ran at WOT for 33 years in your truck???
Wayne's World: I love your boat and I'm gone have one some day. One thing you could do when checking your oil is see if it turnes darker sooner than expected. Over heated oil will darken even though it's still clean. You can be our test rat.:grin: It's all good. ... Ron
My marina owner Ron was driving. Where i boat is a partying town. Check it out. http://www.sylvanbeachny.com/
I have twin oil coolers they came with them installed when it bought her, :smt001
Another speed reader. :smt021. Chuck, Reread my post. :smt001. For a mack its 2150rpm's WOT. :smt038. No !! I've been driving truck for that long
I'm not gonna call anybody an idiot since I don't work on boats for a living but, once upon a time I made my living as an ASE cert mechanic and also built 355's for an All Pro series car that turned 8k and was built to do so. They were overhauled frequently...
I don't run my engines at WOT for more than 10 min at a time. :thumbsup:
The whole thread was could you run @ WOT not that they do. Yes you can run WOT does it put more ware and tare on the equipment, absolutely but they aren't delicate vessel's that you have drive like a Ole Grand Pa all the time so let her rip once and a while it isn't going to ruin them and besides it's fun and isn't that what it is all about?
This should be enough to put an end to this debate.
I also have ASE Master Tech certifications and have had many victories assisting neighbors at my marina with repairs in many areas with their boats saving them alot of $$$.
Nobody would disagree that marine engines life expectancy will be shortened from excessice Rpm's, heat, lack of maintenance, excessive Rpm's (such as when props are out of the water) or anyhting else than can be classified as abusive. So where is the argument?
I hope the negative comments listed were made with humor in mind, and not intended to be as cruel as they appear.
I enjoy reading CSR, but sometimes the banter goes over the top.
Which is better Reebok or Nike? 2 people can argue all day long........
Assuming you keep up the matinenance (e.g. oil/filter changes every 50hours, impellers every 2 years) how many hours can you expect to get out of the 7.4L 310ho engines?
Welcome back Gary!