Where to look first?

[bobbylx]

Hello all, new poster here.

I just purchased a new to me boat today. The seller told me that back in September it started overheating while he was fishing and while he was limping back to the ramp he thinks he spun a bearing. He didn't really go into detail on why he thought that or exactly what symptoms he was seeing or hearing.

So, my question is where should I start with this? The engine is a 1984 Mercruiser 140 3.0 liter with Merc outdrive.

I figured my first step would be to hook up the battery and just bump the starter to make sure the engine rotates? Maybe hook up the muffs and see if it runs?

I did download the Manual posted in another section of this forum, so I've got some reference.

Any suggestions, I just don't want to do more harm than good?

Thank you.

 

[HT32BSX115]

Re: Where to look first?

Howdy,

Well, I hope you bought the boat with the idea that you may be replacing the engine.

If it overheated before, the first place I would look is at the raw water pump located in the lower unit.

then I would have a close look at the thermostat, housing, exhaust manifold and riser for rust that might be clogging the cooling passages


There'll be several people jumping in here with ideas....those above are just a few places to start.


Good luck..


Rick

 

[mthieme]

Re: Where to look first?

What made the previous owner think he spun a bearing as opposed to some cooling system malady?
What's the oil look and smell like on the dipstick?

 

[bobbylx]

Re: Where to look first?

Hello again. First of all, yeah, I bought the boat with the assumption that I may have to replace or rebuild the engine. Thank goodness the boat was cheap.
Thanks for the info, those both sound like good starting points. He definitely said it was overheating so anything dealing with the water circulation I will check.
Also, I'm not sure what gave him the idea that he spun a bearing, that was all he said. I will check the oil also. I am a fairly good auto mechanic so I should be able to recognize the problems when I see them, especially stinky or watery oil.

Thanks.

 

[mthieme]

Re: Where to look first?

BTW, Welcome aboard.

 

[chiefalen]

Re: Where to look first?

HT gave it to you straight. Start it with water going to the drive. Run it till it's warm shut it off.

Compression check done the right way. If it don't want to turn over post and it's a long post so i'll just wait till we get to that bridge before we try to cross it.

Post the the numbers.

By the way i got that exact motor in my boat.

 

[Don S]

Re: Where to look first?

A compression check is not going to tell you if you have a spun bearing or not.
What you need to do is hook up the muffs and start it. If the pump is dead, OH well, you won't be running it more than a few seconds.
Start it up and run it (keep it around 1000 rpm) for 10 or 15 seconds and listen to the engine. Is it knocking? If not. give it some quick throttle and back to idle and listen to what it sounds like.
Keep it all under 15 seconds and you should burn anything up.
The cooling problem is minor if if the engine has a spun rod or main bearing that would cause a loud knocking sound.