How much stress on an engine in a jet boat?

[AntRant]

How much load does a jet put on an engine? For instance... I took my 460 out of a 70's Lincoln Mark III , Now what does the engine think? Would it be equel to puting the car in second gear for start to wide open?

[HammerDown]

Well I dont know what the engine would think...however the stress/load in a boat motor is alot higher than the auto and the marine motor never gets a break unless ya come to an idle...its like driving up hill none stop...or even driving your car with the emergency brake on.
About the red line thing...what ya see on your in dash tach (auto) is conservative...I have no reservations about reving my 468 to 5500, and I'm sure it could take more rpm...but thats just for a few seconds. Now in a auto with a trans...I dont see any issues with droping the clutch at 6000+. And small Blocks seem to take higher rmps longer. It all boils down to the environment the motor is in, Marine/auto and also the condition that perticular motor is in.
If pushed to hard. Anything can and will blow...eventually, just a matter of time.
[ February 20, 2003, 11:17 AM: Message edited by: HammerDown ]

[AntRant]

HD, Havent heard or spoke to you in a while.....Thanks for the info. Going to Owasco Lake in July?

[HammerDown]

AntRant:
HD, Havent heard or spoke to you in a while.....Thanks for the info. Going to Owasco Lake in July? At this time I would say no...but everything with this up and coming summer is a coin toss.

[Blown 472]

The thing to keep in mind as a car is going the load is decreasing, that is why they have trannies to move the mass, jet boats are diff the more rpm the motor builds the greater the load on the motor.

[Mandelon]

How is the load greater? Once the boat is moving, doesn't it take less energy to move it faster than it does to get it going from a standing start? If you were idling and pushed it immediately to say 3500 rpm, it would come on plane and cruise. How is it working harder at a given rpm, its still moving the same amount of water...isn't it.???
Revs come up, and the impeller spins faster. I don't see how the load would change much......It might cavitate at the start.....Splain it to me, Lucy!!!
[ February 20, 2003, 07:11 PM: Message edited by: Mandelon ]

[1tricky1]

I would have to agree with Mandelon. Actually I would suspect the load would be less in your typical 18-20 ft jet application. I believe the motor spins more freely in a jet vs car application. Think about it, when you stab the throttle in a jet, it revs very quick, alot quicker than in a car, unless your on ice or something. But Hammerdown is right in the sense that a jet motor will continue to work harder even at cruising speeds just because a jet needs rpm to work. Regardless, I bet that 460 is much happier in the boat

[jim@pj]

The 460 will have to run in a much higher RPM band all day long. High Rpms will eventually wear a motor down if it is not built for it. The ford auto has rear end gearing and a tranny, you don't drive around all day at 4000 RPM. On top of that the auto engine has a cam designed for a different power band. The 460 is a good motor and if you take care of it and don't beat it to death it should be fine. Good luck Jim

[Hal]

A jet pump is the same as a dyno. The more RPM you turn the more power you will need. Its like trying to push a loaded dump truck with your car.

[Hal]

How in the hell did I lose a star? I did'nt deserve that. I don't do bad things, I only try to help when I can.