When an engine needs rebuilding...

[Howard Sterndrive]

On this board, there seems to be a lot of threads where the poster says their i/o engine exhibits symptoms of needing a tuneup. e.g hard starting, rough idle, low power out of the hole, loss of top end speed

But then, in so many instances... they then say they want to "rebuild the engine" or have it rebuilt, to correct it...

I can't understand where that comes from. I can't find any reference here that says an engine rebuild would be the solution to ANY of those sorts of problems.

In my humble opinion.... you rebuild an engine for 1 of maybe 3 reasons:

1. Loss of oil pressure due to worn internal components (bearing issue)
2. Excessive blowby/loss of compression due to worn internal components (ring/cylinder wall issue)
3. catastrophic mechanical failure of internal components (e.g. spun bearing or failed piston)

and then, you can pare that all down to One common denominator:

Excessive Wear or Failure of Internal Components

If your engine does not have Excessive Wear or Failure of Internal Components then it does not need rebuilding.

What it needs is diagnosing of the systems such as fuel and ignition and a proper repair, adjustment or replacement of components external to the engine.

 

[Howard Sterndrive]

Re: When an engine needs rebuilding...

To condemn an engine to the rebuild shop involves some common processes:

1. Compression testing the engine. If it has low compression on all cylinders, it may simply be worn out.

2. Oil pressure test. The rule of thumb is 10 psi minimum per 1000 rpm of engine speed. But consult the manual for your engine for specs. And mind the recommendations for oil viscosity at a particular ambient temperature before testing.

3. Stethoscope/Borescope/Eyes/Ears/Nose.... An experienced technician interviews the boat owner about the history and hours on the engine. Not necesarily trusting an hour meter (so many are foolishly wired to run if the key is left on) Also using one's 6 senses in Listening to the timing chain, cutting open filters with a proper filter cutter tool, reading spark plugs, examining leakage around crank seals and gaskets are all indicators to how old and tired an engine may be.

 

[boatguya1]

Re: When an engine needs rebuilding...

One of the main reasons an engine needs rebuilding is the mechanic is short of money on the house/truck payment.

James