'88 wellcraft w/ Volvo 3.0 knocking....rod bearings?

[OldBlue22]

Ok I posted a week or so ago wondering what was causing an inconsistant knocking in my engine but had not narrowed down the area. Well I had a friend come over and take a look....He listened with a stethascope and said that the noise is from a rod bearing. ANother friend said you could get a whole kit for the engine to fix this.....true?
I really do not know much about engines.....
Is this fixable or worth fixing?
How much should i expect to pay for parts and labor?
Is there a manual that break it down for me so i know whats going on and could try and repair myself?
has anyone else dealt with this issue?

Just trying to learn more about the boat in general and the issue at hand.

Thanks in advance for your inputs

 

[ken_23434]

Re: '88 wellcraft w/ Volvo 3.0 knocking....rod bearings?

The simple explaination:

Rod knock is caused by too much clearance between the rod bearing and the crankshaft. The excessive clearance is due to the bearing having excessive wear (likely due to lack of lubrication).

To repair, the motor will need to be pulled. At a minimum, you will need a new rod bearing. If the old bearing was completely wiped, then damage would have been done to the crank and would require turning of the crank or replacement of the crank. To determine the full extent of the problem, the crank would need to be inspected and checked for wear.

Yes a kit can be ordered with the required parts. At a minumum, you will be looking at rod and crank bearings, along with gaskets. There are other parts frequently considered "a must to replace", such as the oil pump, timing set, piston rings ...

There are many things that "would make sense" to take care of when the motor is out, but it all depends on how much $$ you are willing to spend.

If you can pull the engine, a regular machine shop can do the inspection and rebuild of the engine (if desired). You do not need to have a Marina do the engine work.

Even though the engine is a Volvo 3.0, the engine is really a GM 3.0 engine. The "Adults Only" sticky has genuine Mercruiser service manuals. If you download the one for a Mercruiser 3.0 engine, the disassembly and reassembly instructions for the engine will essentially be the same as your Volvo (both GM 3.0 engines). The steps talking about the engine mounts, carb, heat exchanger and other "external" parts might be different. The internal engine stuff will be the same. Reading those sections will give you an idea of what you would be getting into.

 

[OldBlue22]

Re: '88 wellcraft w/ Volvo 3.0 knocking....rod bearings?

WOW thats about how my friend broke it down for me too.

I wouldnt mind doing a few extra things to the motor while its out if it will save me from pulling it again later! but i am on abit of a budget.
Where would i pick up a rebuild "kit"?
could this be done by an average joe with tools and a manual?
Should i just try and find a used motor instead?

 

[ken_23434]

Re: '88 wellcraft w/ Volvo 3.0 knocking....rod bearings?

The Sales section of this website will probably have the rebuild kit, or individual parts as needed. You could also probably get them locally from a machine shop.

You might want to check with a local machine shop and ask how much they would charge to rebuild the engine. You would need to pull the engine and deliver it to them. If they would do the engine pulling, it will run a lot more.

Can it be done by "average Joe" with hand tools and a manual? Yes, however, he will become something more than the average Joe at that point.

I would wait to order any parts until the engine is taken apart and inspected. If the crank needs to be turned any, then you will get a different set of bearings (they will be slightly thicker). If you bore out the cylinders, then the pistons and rings would be different.

At a minimum, I would pull the crank and have it inspected. If the bearing surfaces are smooth and mirror like, then they are probably good and no damage was done to the crank. In that case, you might be able to just get away with putting new bearings on the crank and rods. Basically just rebuilding the bottom.

However, with the knock, there is a change that there was an oil supply problem to that bearing, so the hole that supplies the oil should be verified clear. If there was jots of damage to crank and bearing the metal particles might have circulated through out the engine via the oil system. Then, there would be concern for damage elsewhere (metal particles blocking oil passages to other bearings, for instance).

So, you won't really know how much you are getting into until you get into it, unfortunately.

But, you (or average Joe) could strip down the block, take the block, crank and head to a machine shop and have them clean it, hone it, polish, etc... and then the average Joe could reassemble the whole thing. It's really just a big jig saw puzzle, put together with a torque wrench and in a specific order.

I haven't checked, but a rebuild kit with all bearings, piston rings, new pistons and gaskets would probably run less than $300. Just getting the bearings and gaskets, probably less than $100. Machine work on the block, crank and head depends on what they do. Just basic cleaning, inspecting and honing the block would probably run in the $100 range (assuming you disassebled the engine for them).

Hope that helps you.