Engine: No question is a dumb question?

[BUCK N DI]

I will be installing a rebuilt 1988 GM 3.0 liter engine and a rebuilt Mercruiser Alpha 1 lower unit in my "88 Starcraft Islander as soon as the snow melts and the temp. warms up here in northern Wisconsin. The engine has been run on a test stand and checks out good. According to Mercruiser manual, the engine needs about 20 hrs. breakin. Can some of those 20 hrs. can be put on the engine using ear muffs? Or do the breakin hrs. have to be put on the engine while it is under a load, ie. pushing the boat thru the water? Also would like to know if a full 20 hrs. is necessary for proper breakin time? If not, what would? <br />Thanks, <br />Buck

 

[BUCK N DI]

Re: Engine: No question is a dumb question?

Really need your advice.

 

[SeaDawg]

Re: Engine: No question is a dumb question?

Test stand would give you a good start. I would run it a varying speeds, but not over 3,000 with no load on the motor.<br /><br />I would run it 10 hours or so, on the stand. That is, if you can stand it (it would be boring work, for sure) You will then know if any serious problems are going to come up, like loose parts inside the engine, etc.<br /><br />To me, it's better to find out on the stand than to get it in the boat and then blow it up.<br /><br />If it were mine, I would still baby it for the next 10 -15 running hours, after I installed it in the boat.

 

[robsd]

Re: Engine: No question is a dumb question?

I disagree slightly. The break in should be in the boat. You want to put some load on the engine to allow the rings to seat or they'll glaze over. Usually what it calls for is some half to 3/4 runups (under load) then plenty of cool down time. You don't want to just idle it around for 20 hours. You also don't want to over do it. Think of it like a car. <br /><br />A good hour or so on the stand is good for checking and fixing oil leaks and such.<br /><br />Good Luck,<br />Rob

 

[Dennis4b]

Re: Engine: No question is a dumb question?

I've always been told not to let the engine run too long on earmuffs, maybe a minute or 2 at a time, but that's about it.<br /><br />I don't know how to back it up though, so any comments are welcome

 

[novacane]

Re: Engine: No question is a dumb question?

run it up and down in rpm to seat the rings <br />and go for it,thats it,ive built alot of race motors and thats how ive always done it with no problems like nascar thay toss in a fresh motor run it 20 mins good to go,that 20<br />hours is hog wash

 

[DJ]

Re: Engine: No question is a dumb question?

Buck and Di,<br /><br />Plan for a romantic day on the lake at displacement speeds.<br /><br />The engine needs a load to break in. Even more importantly, varying speeds!

 

[BUCK N DI]

Re: Engine: No question is a dumb question?

The engine already has between a half hour and an hour on the test stand. I've got a Mercruiser Maintenance Manual for the boat so I'll give it the recommended breakin with varying rpm and speed. Was hoping that one of you guys with the experience and knowledge would say that the full 20 hr. breakin period could be shortened up a little. The big browns are biting on Lake Michigan and it's only a couple of weeks til the cohos start hitting on Lake Superior.

 

[robsd]

Re: Engine: No question is a dumb question?

Buck....just go a bit slower and leave a little earlier. You'll get to the fish. <br /><br />Rob