New 4.3 Is In Finally! Break in recommendations?

[brsox88]

So I finally have the cracked 4.3 back into my 18.5 starcraft and going to be taking it out in a day or two. What is the break in period and recommendations? And when should I change the oil?

 

[alldodge]

If this is a flat tappet cam you need to run it quickly up to 3000 rpm and then vary from 1500 and back up for 20 minutes. Don't do this on a hose unless your drive is removed (assuming Alpha).

Here is the break in procedure
http://www.cranecams.com/uploads/breakin/548e.pdf

If this is a roller cam, then just take it easy and no WOT for first 10 hours, Try to vary the engine load and rpm as you go

 

[brsox88]

This is just a 4.3l 262 I got from rapidomarine.com, so I think its just a roller cam from what I saw. How else would I know if its a tappet cam? And after 10 hours I assume is when I should change the oil?

 

[alldodge]

Look at your receipt it should tell you which motor was bought, then go to web site and see what they used, or give them a call.

Yes change the oil after 10 hours

 

[brsox88]

Yeah, its a roller cam so I guess I'll just try to take it easy. 10 hours seems like it could take a while. What does the variable position in throttle do for the engine, just prevent it from wearing into one same spot?

 

[alldodge]

This is out of the manual, and I'm a worry wart with break in procedures. but for the most part you vary the load to let the rings start to seat. The motor needs to run up to full temp and cool back down several times to get everything wear in, so to speak.

Use care during the first 20 hours of operation on new Mercury MerCruiser engines or
possible engine failure may occur. If a new engine has to be water-tested at full throttle
before the break-in period is complete, follow this procedure.
1. Start engine and run at idle rpm until normal operating temperature is reached.
2. Run boat up on plane.
3. Advance engine rpm (in 200 rpm increments) until engine reaches its maximum rated
rpm.
IMPORTANT: Do not run at maximum rpm for more than 2 minutes.

 

[MBAKER]

I did some work in an speed shop a few years ago and when we built race engines there was never a 'break in' period. With roller cams, once we started them and got them up to temp and checked for leaks, overheating, etc we would go straight to dyno pulls or in the car and race. With cylinder finish and rings these days they will seat fast. If it were my boat, after I had it running on land, Id put it in the water do a half dozen 1500 to WOT runs and call it good then use it how you want. I know that's not what manufcturers say, but in reality if its gonna break its gonna do it right away running it easy for a given amount of time isn't going to change that. If its flat tappet, then you need to take care to get the cam broke in, but even at that 20-30 minutes and run with it.