Belt broke on Merc120. How bad off am I?

[JeremyL]

Hello,

I am brand new to boats, as will become apparent in this post. I'm learning fast though, and appreciate any help you can offer!

I bought a 1985 bowrider with a Mercury I/O 120, S/N is in the highest range for the model.

Boat drove fine for the first few outings, but the belt started to squeal at the very end of one trip. I put the boat in again the next day, and sure enough the belt broke on that trip, but not before I noticed several other issues that may or may not all be related. The goal of this post is to determine if I've wrecked my engine beyond reasonalbe repair, or if I should attempt to fix its issues.

Here are the symptoms:
Belt Squealing, now broken. I drove the boat about a mile after the belt broke, at the lowest speed possible.

Power steering wonky, but that makes sense since that unit is on the belt path.

Before the belt broke, the engine was overheating. Having read other posts, that seems to be an issue with the impeller or water pump that is in the outdrive... and I'm gathering that I have to take the outdrive off to check its status. Can the failing belt be responsible for any overheating, or is that an independant issue?

I'm concerned that between the overheating issue and having run the engine (albiet slowly) with the belt snapped, that my cylinders got too hot and are now siezed. I bought a new belt today, and I'll be able to tell soon if my engine is seized, but I'm wondering if one of you guru's can point me toward other potential catastrophic issues my situation could have caused, and the best ways to check the critical systems that may be affected.

Thanks for any advice you can offer!

 

[HT32BSX115]

Re: Belt broke on Merc120. How bad off am I?

Before the belt broke, the engine was overheating.

I'm concerned that between the overheating issue and having run the engine (albiet slowly) with the belt snapped, that my cylinders got too hot and are now siezed.

Howdy. It doesn't matter how slowly you ran the engine. How hot did it get before you discovered that it "overheated"?

Boat drove fine for the first few outings, but the belt started to squeal at the very end of one trip.

I hate to "beat" you up over this, but do you think you maybe should have investigated the "squeal" immediately after it started doing it?


Was the temp gage "pegged"? (sometimes the raw water pump can move enough water through the engine to keep it from severely overheating......but I wouldn't "bank" on it....)

Was there smoke? Did the engine ping severely and NOT turn over with the starter after you shut it down?


If the engine is indeed "seized", you can probably plan on replacing/rebuilding the engine.


If your exhaust system didn't start smoking, your raw water pump may have been moving enough water to keep from burning up the rubber parts etc....


Not running with the belt on will cause an overheat because cooling water cannot circulate though the block and head.......


Good luck,


Rick

 

[fat fanny]

Re: Belt broke on Merc120. How bad off am I?

Well you definately fried the impellar and as for the cylinders the jury is still out on that one but 1st off go to merc stuff .com and the imellar change directions are in there or by a service manual. But as for the engine it'self I would invest in a harbor frieght compression gauge 20.00 and test all cylinders compression max should be around 150 or so pull all plugs and rotate by hand with wrench and or wratchet on crank belt pully nut or use starter (best method) you will know then if you blew the head gasket! But as for the impellar I think it's 6 bolts and drop the lower leg and replace the inplellar and housing and all other seas and gaskets that come in the kit.

 

[chewey440]

Re: Belt broke on Merc120. How bad off am I?

check water pump,alt,and p.s pump. something is frezzing up to make the belt break.don't think lower water pump in out drive is bad. motor might be fine. good luck.

 

[libellav15]

Re: Belt broke on Merc120. How bad off am I?

How many belts have you gone through?

I thought it was just one that squealed and finally snapped - if thats the case then nothing needs to have locked up - the pulleys (alternator/balancer etc) dragging across a belt that is not turning due to slip (hence the squeal) will be the reason it finally gave up.

If the pulleys are heavily corroded give them a rub down and paint - and tension the alternator properly to prevent squeal. Will also make sure your new belt lasts as long as it should.

As discussed above the squeal and related belt slip means that the circulating pump wasn't turning anywhere near enough even before it snapped - hence the overheating before and after the snap.

What makes you think the pots are now siezed buddy?

cheers

adam

 

[JeremyL]

Re: Belt broke on Merc120. How bad off am I?

Thanks for the responses- I see this was the right place to post; Responses below:

>>What makes you think the pots are now siezed buddy?
I don't know that they Are seized yet, when I made it to shore and cut the engine, it Clunked a bit before cutting off, and then there was the heat...

>>>Was the temp gage "pegged"? (sometimes the raw water pump can move enough water through the engine to keep it from severely overheating......but I wouldn't "bank" on it....)

The temp gauge got up to 250F, when I first noticed it, and I cut the engine then and let it cool. Each time it reached 175F I cut and cooled. After the second "cool" session, the belt gave and I didn' tkill the engine again, and the temp stayed at 175F (per the trolling in). Lots of sizzling sounds upon that first stop.

>>>Was there smoke? Did the engine ping severely and NOT turn over with the starter after you shut it down?

Yes. There was white, oily smelling smoke the first time when it got to 250. Only smoke that first cool down time though. At one point, the tube (manifold?) that took water out of the engine popped off, (BANG) and water was indeed dumping into the boat at that point. This tells me that at least Some water was cooling the engine at that point, but that was before the belt snapped. ..I had the right nut driver to re-tighten the hose, so off I went.

>>>I hate to "beat" you up over this, but do you think you maybe should have investigated the "squeal" immediately after it started doing it?

Yes again. The Squeal went away after a minute, so I ignorantly figured I could get away with another trip and replace the belt this week. So Wrong.

>> I would invest in a harbor frieght compression gauge 20.00 and test all cylinders compression-

That seems to be the best place to start, along with assuming the need to replace the impeller.

Thank you all for the replies!

 

[JeremyL]

Re: Belt broke on Merc120. How bad off am I?

How many belts have you gone through?

I thought it was just one that squealed and finally snapped - if thats the case then nothing needs to have locked up - the pulleys (alternator/balancer etc) dragging across a belt that is not turning due to slip (hence the squeal) will be the reason it finally gave up.

If the pulleys are heavily corroded give them a rub down and paint - and tension the alternator properly to prevent squeal. Will also make sure your new belt lasts as long as it should.

As discussed above the squeal and related belt slip means that the circulating pump wasn't turning anywhere near enough even before it snapped - hence the overheating before and after the snap.

What makes you think the pots are now siezed buddy?

cheers

adam

Also: This is the first and only belt thats broken so far. The number on the belt was Napa's old style of numbering parts, and the belt does look old. in fact, the bolts securing the engine are rusted in place, so this belt has been on there a while- Its a bummer those rusty bolts have to come off to get the new belt on;

 

[Silvertip]

Re: Belt broke on Merc120. How bad off am I?

The lesson to be learned here is that manufacturers don't put things on engines if they are not necessary. If they weren't they wouldn't be there. The belt on an engine runs the water circulation pump, alternator, and power steering pump. All of this applies to your car as well. Gauges were installed in cars years ago but manufacturers determined that 90% of the people had no idea what the gauges were telling them so they switched to (pardon the term) "Idiot Lights". Turns out they didn't help either. It seems folks knew that a red light was bad but they also thought that it meant they could drive seemingly forever before they had to actually do something about it. So gauges are currently again "poplular" but they are still being ignored. As others have said -- hate to beat you up over this and really I'm not. I'm just indicating how uniformed boaters are about the vessel they have control of.

 

[JeremyL]

Re: Belt broke on Merc120. How bad off am I?

I take no offense to the lesson. I knowingly took a risk using unsound logic and I'm paying the price for my hastiness. Thx.

 

[libellav15]

Re: Belt broke on Merc120. How bad off am I?

You probably know already buddy - but you don't have to touch the engine mount bolts

on the right side of the engine is a spacer - 2 bolts and its off - slip the new belt in there. And I also cable-tie another belt out of the way while the spacer is out - that way next time it goes its a simple case of slacken the alternator and slipping the new one on.

if you didn't know about the spacer i can get you a piccie of exactly where it is

cheers and good luck

adam

 

[Gary H NC]

Re: Belt broke on Merc120. How bad off am I?

At the very least the exhaust boots from the manifolds got cooked as well as the flapper in the Y pipe....That is the best case scenario....

 

[tupperj]

Re: Belt broke on Merc120. How bad off am I?

Lots of good info here, but I'm puzzled by something.
I've got the same 3.0 in an 86 Sea Ray and I have two belts on the engine.
One runs the alternator and water pump, the other the power steering.
Now, the power steering pump on my engine looks, well, off. Seems like it might be a change over by a previous owner.

So, I guess my question is, should I have one belt for everything, or should it be two?

Paul

P.S. Not trying to hijack the thread, but the one vs two would have an effect on some of the advice given, I think.

 

[JeremyL]

Re: Belt broke on Merc120. How bad off am I?

@libellav15: Right you are! I just figured that out when I actually took ratchet to bolt. The new belt is on, but I don't know about timing it (I need to time it, right?): how much slack should be in the belt?

The exhaust boot does looked cooked and bubbled. What's a flapper in the Y pipe and where is it?

Service manual is now ordered, but wont be here for a bit.

Going to go get a pressure gauge and if I'm good there, on to check the impeller.

 

[JeremyL]

Re: Belt broke on Merc120. How bad off am I?

Lots of good info here, but I'm puzzled by something.
I've got the same 3.0 in an 86 Sea Ray and I have two belts on the engine.
One runs the alternator and water pump, the other the power steering.
Now, the power steering pump on my engine looks, well, off. Seems like it might be a change over by a previous owner.

So, I guess my question is, should I have one belt for everything, or should it be two?

Paul

P.S. Not trying to hijack the thread, but the one vs two would have an effect on some of the advice given, I think.

I only have the one belt, and I'm not sure that I have power steering at all. At least, there is no power steering unit that I can identify. My belt only connects the alternator, and to two large wheels on the main engine block, (crankshaft and water circulator)

 

[HT32BSX115]

Re: Belt broke on Merc120. How bad off am I?

There is a "bottom line" here.....


You have a belt-driven component that is seriously dragging...... Enough to cause your belt to fail. It could be the water pump, PS pump or the ALt.

You NEED to determine which one it is and repair/replace it.


Then you'll need to fix the other problems.


Good luck,


Rick

 

[JeremyL]

Re: Belt broke on Merc120. How bad off am I?

You are very right- Lots of problems found as I dug into the job. There is a fair amount of corrosion to deal with. The water circulator is being replaced, as well as the timing gear cover. I cant figure out how to get the plate just in front of that gear case cover off though.

The alternator spins freely.

The good news that is motivating me to fix everything: I got the engine to turn over after replacing the belt, and it sounded normal (no knocking). I had the garden hose earmuffed onto the outdrive, but no water came out of the propeller. I'm thinking I have a blockage in the cooling line somewhere. I'll get to the outdrive after I get the front end of the engine put back together.

Thanks!

 

[nola mike]

Re: Belt broke on Merc120. How bad off am I?

I had the garden hose earmuffed onto the outdrive, but no water came out of the propeller.

it may not on muffs--water will typically come out of the idle relief ports at the transom, with very little through the prop. water should be coming out SOMEWHERE though.

 

[libellav15]

Re: Belt broke on Merc120. How bad off am I?

The new belt is on, but I don't know about timing it (I need to time it, right?)

Hi mate

no need to set the timing just because of the belt replacement - its purely a drive belt - not a timing/cam belt

cheers

adam

 

[JeremyL]

Re: Belt broke on Merc120. How bad off am I?

Well you definately fried the impellar and as for the cylinders the jury is still out on that one but 1st off go to merc stuff .com and the imellar change directions are in there or by a service manual. But as for the engine it'self I would invest in a harbor frieght compression gauge 20.00 and test all cylinders compression max should be around 150 or so pull all plugs and rotate by hand with wrench and or wratchet on crank belt pully nut or use starter (best method) you will know then if you blew the head gasket! But as for the impellar I think it's 6 bolts and drop the lower leg and replace the inplellar and housing and all other seas and gaskets that come in the kit.

For any other newbs reading this thread: go to mercstuff.com as Fat Fanny suggests and learn some basics. Its a treasure trove of easy to access info.

Thanks Fanny!

 

[libellav15]

Re: Belt broke on Merc120. How bad off am I?

Tell you what...

you couldn't call yourself (or wouldn't want to) call yourself Fat Fanny over here

conjures up all sorts of nasty (sweaty) images!!