Reply With QuoteThrer is a lot more load on a boat than a car engine. How much boat fuel do you use in a weekend. If you put that much fuel in your big block truck how far would you get.
jordanpaulk
[/qb]Depending on the pump set up and its' tolerances, it will rev up quicker due to a certain level of cavitation. Revs up great on the trailer out of the water right? Won't pull the same RPM's across the water now will it? No. The faster the motor runs, the faster the impeller is turning trying to move more water through the bowl which doesn't change due to rpm. The more water that is "waiting" to go through the pump as the motor gets up to the top RPM it will pull in the water, the greater the load. If you were running some type of variable nozzle out of your pump, then perhaps the load would remain constant, however, on a standard pump, like Blown said, the higher the RPM, the more load on the motor. [/QB][/QUOTE]
Jordy, Who ever ever mentioned out of water, trailer revving?I am refering to initial load at full throttle. Of course there are many variables with pump clearances etc, but I'm saying there is more load on that 460 trying to pull that lincoln up to speed from a dead stop than that 460 getting an 18' jet up to speed. Yes, I agree the load will increase across the power band and the faster you go, but initial load has got to be greater in that land yacht
Threr is a lot more load on a boat than a car engine. How much boat fuel do you use in a weekend. If you put that much fuel in your big block truck how far would you get.
1tricky1:
I'm saying there is more load on that 460 trying to pull that lincoln up to speed from a dead stop than that 460 getting an 18' jet up to speed. You have to remember that there are many gear reduction devices in use to get the land yacht up to speed. The transmission, unless you're starting in overdrive, the differential, unless you're running a 1:1 drive ratio, and event the size of the tires all play into how much load is on that motor in the car. Think about it this way, on flat ground, at idle that lincoln will begin picking up speed, even keep the rpms at 1500-2000 rpms or so, you'll keep picking up speed and run through the gears in the transmission. Try that in a boat and see if you ever get on plane.
schiada96:
Threr is a lot more load on a boat than a car engine. How much boat fuel do you use in a weekend. If you put that much fuel in your big block truck how far would you get. You use more fuel in a boat because of more required RPM at cruising speed, not soley because of "load". If that same 460 had no transmission, and had to cruise at 3,000+ all day, believe me, it would use the same amount of fuel as the boat.
I'm saying the load on the engine at 3000 rpm in a jet boat is not the same as a typical truck at 3000 rpm. The boat will use more fuel. Hence more "stress".
How many hours is typicaly good for a marine engine before a rebuild 5 to 6 hundred hours?
Not only that but you have this mass now moving, to which it takes very little hp to keep it moving, like said before. It also has to do with the fact this is a pump, there was a thread on pump dynamics awhile ago, when a pump reaches a certian rpm it will pump said amount of water, above that it takes more rpm and increases the load on the motor to drive it. I believe the sweet spot is a low rpm for the pump, somewhere in the 3000 rpm range.
Maybe i can help clarify the boat/vs car effects on a motor. You change your oil in your car every 3,000 miles right? Well a weekend of running my boat hard will break down the oil in my boat, necessitating an oil change. I dont know about you, but when i drive my boat, i'm at no less than 3,500 rpms all the time (B-cut impeller). And if i'm running with my friends who have fast boats, i'm cruising at 4,500rpm just to keep up. So even a cruise from say Laughlin to Needles (about 15-miles) at 4,000+ rpms constantly is alot of work for the motor.
I agree with you Jordy and others about a boat motor does see more stress than in a car. But what I keep picturing is that lincoln (land yacht) being givin full throttle from a dead stop or even a roll, the tires hooking up, the front end coming up, the motor torking sideways and that "load" being transferred up to the engine. It just seems to me a (jet boat)boat doesn't see that much "initial load" accelerating up onto plane.
1tricky1:
I agree with you Jordy and others about a boat motor does see more stress than in a car. But what I keep picturing is that lincoln (land yacht) being givin full throttle from a dead stop or even a roll, the tires hooking up, the front end coming up, the motor torking sideways and that "load" being transferred up to the engine. It just seems to me a (jet boat)boat doesn't see that much "initial load" accelerating up onto plane.
Posting Permissions