Inboard Jet Break-in Questions

[Beefcake]

I found what appears to be a great deal on a jet boat, and my girlfriend's kid is pretty sure he wants to buy it. It is an older boat with a brand new motor - not broken in yet. I believe the motor is a 350 Olds V-8; not sure what brand the pump is. My question is, what is the "break-in" procedure for a new V-8? Since the boat owner is a friend, we have the ability to borrow it for several days to test drive it and/or take it to a mechanic, but I don't want to screw up the motor on the test drive. Should we plan the first two hours of the test drive for breaking in the motor? Is it the same as my new 4-stroke kicker: idle for 5 minutes, 1/2 throttle for 3 minutes, idle for five minutes, 1/2 throttle for 5 minutes, idle for 5 minutes, 1/2 throttle for 10 minutes, etc.? (I know this isn't exact, but I can look up the times per cycle in the owner's manual from my kicker if it is the same idea).

[suckerfish]

It, s reall not going to matter much because the motor will be under constant load. However, I would very the RPMs between 1800-2200 rpms for the first twenty minutes of run time, and keep an eye on the temp. I would then just run the boat in low to mid rpms and runner up to higher rpms for short durations. Do this for several hours, just to make sure the motor is going to hold together. When you confident with the motor, drive it like you stole it.



suckerfish

[Jettin' Fool]

Also change the oil after the first 10 hours.

JF

[Tacklebuster]

Crabbing is one of the best ways to break a motor in like that if you have a bunch of pots out. The twenty minutes of 1800 to 2200 is critical and then after that go crabbing for 8 hours. You will be on and off the throttle all day at all ranges of RPMS, just don't open her up for an extended period of time until she is all broken in. Then check your manifold bolts and the such and tighten if need be.

[Quiet Riot]

If its a flat tappet cam, then set timing and run at 1800-2400 rpms for 10-15 minutes and shut off and allow it to completely cool. Then gradual run ups to 3000, and 3500 rpms and keep varying the rpm (don't keep it stuck at any specific rpm for more than a minute or two.) The key is to let it completely cool afterwards and repeat. After a couple hours it should be good to go.

If it hasn't been run in awhile (or ever since rebuild) I would definately remove the distributor and prime the oil pump with a primer and drill (primer can be bought at auto parts store) before firing the engine. If its not a standard 3point mount it would be easier to disconnect the pump and run it off a water hose in the driveway. Otherwise just putt around the dock for cam break-in with motor cover off to watch for leaks/issues.

If its a roller cam with moly rings (not likely if it truely is an oldsmobile motor) than fire it up and once the oil is warm, wring its neck.........

jd

Ps. its always a good idea to change the oil after a few hours of use and cut the oil filter open and inspect for debree (shouldn't be any metal flakes, etc) as this will show signs of problems with a new engine. And ensure its broken in with conventional motor oil.

[IDWITHELD]

If it's a flat tappet cam, I'd probably walk away from that motor. What shape is the pump in? How many hours? Did anyone rebuild the pump? If the motor needed a rebuild I expect the pump is ready.