View Full Version : High RPM??

local 11 spark
02-17-2008, 12:03 PM
Had my new boat out yesterday, for one short run I gassed it to top end speed, and the tach was reading 4500 rpm. Is it safe for the engine to go that hard or harder?? I've got 11 hours on it... 8)

02-17-2008, 12:52 PM
With 11 hours on it I don't think you hurt it but I wouldn't keep the RPM's up there long.

local 11 spark
02-17-2008, 01:14 PM
But, as I get more hours on the engine, is that high of RPM's normal??

02-17-2008, 02:43 PM
WOT (wide open throttle) should have revs in the 4800 range.
Short answer.....yeah, you're good.

02-17-2008, 04:27 PM
For the old Chevy 350 (5.7L) block yeah that is approaching the upper limit.

02-17-2008, 09:03 PM
Butta's right..............4800 is normal for WOT.

These engines are extremely tough, but its not recommended to run them WOT for any extended period of time.

If your under a load, footing for instance, I never worry about it cause the rpms never reach the max due to the ski load.

02-21-2008, 12:02 AM
I have to laugh a little bit here for the old 350 chevy block that can be called "high" rpms, for a BMW 4.4 Liter V-8 block she is just starting to get exciting at this rpm!

02-21-2008, 07:24 PM
Actually zeg, I've been told that the Indmar engine is built from the Corvette platform and is actually a high rpm block. Indmar beefs the engine up, lowers the compression and programs the computer for lower rpms to increase durability.

While you won't find it in the manual, I have some friends in the know that claim that the 325 Indmar can run all day at max rpm.

Although, I don't recommend trying it........ :D

02-21-2008, 08:14 PM
Actually it is the old small block Chevy engine. The 6.0 Liter is the new Chevy block with the Aluminum heads and the roller lifters which is the same block that is used in the Vette (1996ish) and all SUV's and trucks since 1999 at which time the old 350 was killed off production GM vehicles! This block is 4.8L, 5.3L and 6.0L versions based on bore and stroke.
It is a new design but still old technology. It does not have overhead cams or 4 valve cylinder heads. As a boat engine it is perfect because it makes great low end torque, as a high performance high tech engine it ranks low on the scale. Even the new Ford V-8 which has been out close to 20 years has overhead cams and if you get the cobra you get twin cams and 4 valve cylinder heads. It boils down to cost and it is cheap to make an engine with pushrods (100 year old technology) than it is to make one with overhead cams and especially twin cams and 4 valve heads. You could get a Vette in the late 80's and early 90's with this feature (the engine was made by Mercury for GM) but no one bought it and it was discountinued. My 1997 BMW 4.4 Liter V-8 (268cubic in) makes 292Hp (rear wheel which is another issue add about another 15 to 20% for at least 335hp at the crank) and 325ftlbs of torque (variable twin cam 4 valve heads) while the small block 5.7 Liter which we all know as the small block chevy 350 makes 325hp. Anytime you make more than 1 hp per cubic inch you are doing very good! Don't get me wrong I have owned and own several Chevy trucks and I love them, but I also own a 100% aluminum BMW engine in my 540i 6 speed and I really love this one! But we don't need that in a boat and I don't want to pay for it either!

02-24-2008, 09:27 PM
Small block chevy's are famous for turning some high rpm's , Factory motors probally still put red-line at 55-5800. They arent designed to stay at that range long without some serious engine building, how those nascar motors stay together at constant 85-9000 blows my mind, boy would I love to of gotten hold of one of those babies in my early days! I have been known to "pump" one up to about 7500 and side step the clutch :shock: wow what a rush ! I loved it. For our boating purposes lets stick with the reccomended 4800 WOT for short burst, I baby the heck outa mine, I very seldom run it over 3 grand.

02-25-2008, 09:44 PM
Again Butta is right 4800 WOT and you are safe at your little burst. I doubt it very much that you could hurt these engines if you got even to 5600RPM. Heck we run close to 10000RPM on our champ sled, I know it's a custom built race motor but it isn't nearly as beefy as a 350 small block. Part of the problem with higher reving engines is the octane requirments. Z, I doubt your Dub runs worth beans on 87 octane. You need more like 93. I think they keep things tuned down for several reasons. Durability, Ease of use, Cost of operating, general user expectations.

02-25-2008, 10:01 PM
Yeah Sled you are correct she runs better with 93 due to the high compression, but she will run with the lower grades, the knock sensor will just retard the timing which in turns causes a loss of power, which is why I only put 93 in her. I mean what IF a Honda with a big huge chrome plated Noisey muffler starts to think he is bad, you know the dude with the pants around his knees! The issue about turing high rpms has to do with mass and valve springs. Bigger motors just don't turn the RPM's and anyone who thinks 7k is a lot of RPM's has never watched a F1 race car where right now they are limited to 20,000RPM! 3Liter V-10's cranking out close to 1000hp without turbos! The piston skirt speed on these things are approaching supersonic! But then go down and get a Cox .010 engine (I think that is correct) and it will turn over 20k easily. And a good 2 stroke 125cc without the valve float associated with 4 stroke valve train!!!! Then what is the Max RPM of the diesel engine in the Queen Mary II, less than 500?

local 11 spark
02-25-2008, 10:09 PM
fu#*ing motorheads!!! HAHA!!! I really appreciate everyones input here. This is a GREAT forum, for getting info.
Again, thanks... 8)

02-25-2008, 10:18 PM
Hey we're full of all kinds of useless information, just keep asking the questions and we'll keep you updated with all the latest crap 8)

Hey it's what we do :D

02-25-2008, 10:49 PM
Guys!!!! You don't understand the real dilema here!!!!!!
They are starting on our boat tomorrow!!!! I have to find a way to pass the time!!!!!!!!! Every time I walk out of the house I pass by the Old MasterCraft and it just makes it worse!!!!

02-26-2008, 06:25 AM
That's why I bought off the Boat Show floor, Z. The only wait I had was until the Show ended (bout 3 days). Then it was plug 'n play.

02-26-2008, 12:59 PM

I guess since we finally decided to buy a new boat (and spend this amount of money) we wanted to be outfitted just like we wanted. If the boat at the show was blue and had a z-cargo bimini it would be here now too! But she was red and while that is not a bad color we really wanted the dark blue to help hide the stain she will get on her hull sitting in the water all summer. I even joke with my wife that maybe we should just launch it when we want to use it, but with the dock in the backyard it is so nice to just come home and go skiing! My wife said we just need to wash it as it sits in the water. I said OK I will bring the gun down to the dock and you wash it while I watch out for gators! we have 2 that live near the dock, you can hear them, they sound like bullfrogs on steriods!

02-26-2008, 03:41 PM
I've always wondered about riding near gators. How do you do it? They don't bother you? My wife would like to move south for warmer weather...

02-26-2008, 04:04 PM
OK long story, we moved here 5 years ago from Atlanta, there are no gators there. We live on Deerpoint Lake and yes there are gators here. I have seen a 5 to 6 footer near the slalom course but generally on the open section of the lake it is very rare to see them as this section has houses all around it. Go up the 3 creeks that feed the lake and there you can see some very large ones but you wouldn't ski here. About 4 years ago my wife, my son who was 6 and I were on the Chattahoochee river not far from here teaching my son to ski. Well he kept falling from side to side so my wife puts on her vests jumps into the river and holds him to keep him from falling. We go and he gets up and goes 100 yards!!!! I turn the boat to get him and see my wife doing a backstroke like she is in the Olympics!!! She is screaming my name so I grab my son and run back to her. She is in the boat so fast I can't quite figure out how she jumped out of the water like that. She screams at me did you see him? See what I replied and then pointing to the other side of the boat she says HIM!!! I look at a 6 to 8 foot long gator swimming away. Just after I hit the throttle she saw something moving on the bank! It was him, he left the bank and swam out towards her!!!! We never ski in this river and we shouldn't have to begin with, it is in the middle of the wilderness. That day alone we saw 4 more gators on that river. It took one year and the purchase of a 9mm ruger before my wife would get in ANY water again!!! We also put a Garmin fish finder on the boat too! Not just to make sure the water is deep enough but to see HOW big the fish are around us! But honestly I have never met anyone else who has had a problem with them and yes the water gets to 88-89 degrees on the lake in the summer!!!