Timing belt broke, some questions...AQ125A

[2stroke1971]

Lost a timing belt last night on the water. Not fun, I know what to do with it but I have some general questions.

My pulleys had been rusted at one point....when I rebuilt the motor last year I cleaned them off and they stayed pretty nice last season. over the winter lots of things in there got rusty again including the tensioner and I bet the pulleys although I cant get a good look at them just yet.

Previously, even after wire brushing them there were some pits....the cam pulley was fine, the one that drives the sea water pump and distributor was pitted....the main engine pulley was not that bad.

if they are brushed again, would the pits cause premature wear?

Lets just say I replaced all the pulleys...how long could I expect them to remain clean? How long should I get out of a new timing belt? Is there any there any kind of coating that can be done to slow the rust down?

Thanks in advance....

 

[Nickypoo]

Re: Timing belt broke, some questions...AQ125A

How are the pulleys getting rusted? Do you store your boat outside in the winter? What kind of failure? Catastrophic? Teeth ripped off?

You get some cold temps overnight in Baltimore during the winter. I don't think having the exposed timing belt set in the same position all winter under tension helps longevity.

You might be able to paint your pulleys but I doubt it would last long. I've been powdercoating all my stuff including the pulleys, but I have no idea how long it will last since my project isn't finished yet. Powdercoat is supposed to be very durable. Here are my pulleys getting powdercoated:



If they are pitted a lot then you should probably replace them.

Also make sure there isn't any abnormal drag in any of the pulleys. A binding impeller can tear the teeth off a belt.

I'm assuming that you store your boat during the winter, but perhaps you use it all year.

 

[2stroke1971]

Re: Timing belt broke, some questions...AQ125A

How are the pulleys getting rusted? Do you store your boat outside in the winter? What kind of failure? Catastrophic? Teeth ripped off?

You get some cold temps overnight in Baltimore during the winter. I don't think having the exposed timing belt set in the same position all winter under tension helps longevity.

You might be able to paint your pulleys but I doubt it would last long. I've been powdercoating all my stuff including the pulleys, but I have no idea how long it will last since my project isn't finished yet. Powdercoat is supposed to be very durable. Here are my pulleys getting powdercoated:

View attachment 144987

If they are pitted a lot then you should probably replace them.

Also make sure there isn't any abnormal drag in any of the pulleys. A binding impeller can tear the teeth off a belt.

I'm assuming that you store your boat during the winter, but perhaps you use it all year.

The boat stays on the trailer outside year round, we use it from April to November...the belt broke, just snapped apart. The teeth looked square, not beat up. This belt had one season on it and five times out this year so far...I would guess about 35 hours in 35 launches-we don't go very far and I am fairly easy on it, chugging from one spot to another....except that when it broke it was the first time I had it up to about 20mph in a while.

When it rains heavily, the boat does get damp inside, my covers not the best so its not uncommon for me to pull the cover on a sunny day and lift the lid, and the whole engine has dew on it!

As i sit here and write this, It came to me... that night, about 10 minutes run time before the belt broke, we were in the shallows trying to dock somewhere odd and the prop hit something and it stopped the motor cold. Got a nice ding in the prop, Im sure it hit a big rock--they were all around the shore there. We were just chugging and trying to dock but Im thinking the prop stopping cold like that may have sent a shock through the drive train and caused the belt to stretch or weaken....so that later when I was turning 3500 rpms, it broke....it was a pretty crisp break.

Hmmmm....

 

[Nickypoo]

Re: Timing belt broke, some questions...AQ125A

That's very interesting. I wouldn't normally think the rotational inertia of the camshaft and secondary shaft alone would be enough to cause such a failure in the case of immediate stoppage, but your theory seems logical.

What brand of timing belt was it? Is there any chance it was a cheap one?

The way it failed tells me that the condition of the pulleys didn't have any influence, especially since the teeth on the belt looked so good.

It could have been a lethal combination of a faulty belt and your prop striking the rock.

 

[2stroke1971]

Re: Timing belt broke, some questions...AQ125A

Yeah, to be honest it was a cheap belt.

I know my local Volvo dealer has one for about $42, but its an aftermarket brand, not sure what exactly. I had bought and used one of those for one season.... but when I pulled the motor for the rebuild I replaced that one with the cheap one that broke.
I tore everything down today so Im gonna go through all the bead blasting and painting again. The pulleys and tensioner were nasty for sure.

 

[2stroke1971]

Re: Timing belt broke, some questions...AQ125A

oh yeah, the dampener for my sea water pump is obliterated....unreal. Once a season for that part. If you are a really bad piece of metal, the gods of the mechanical kingdom will re incarnate you as a marine part.

 

[Nickypoo]

Re: Timing belt broke, some questions...AQ125A

If you are a really bad piece of metal, the gods of the mechanical kingdom will re incarnate you as a marine part.

Haha seriously!