How long do freshwater small blocks last?
 

Hi all. I am contemplating some engine work over the winter and it occurred to me that my motor is 25 years old. It's raw water cooled and every year when I drain it I have to poke through rust scale in the water jacket. This boat has always been up in the north, so it gets 4 to 5 months use each each year. The motor has good compression and runs fine. My concern is how long I can expect to keep it before the water jacket or something else in the block fails.
If any of you have had issues like this I'd be interested to know. Also are there any common areas in a small block where such things happen, and is there a way to check condition? Or slow the march of time?

Opinions and facts are all welcome.

If the motor was full of coolant I wouldn't ask, but with water, I wonder what to expect.

My Formula is a 79. The motor blew last year. My machinist tanked it, checked the block real good and he said it was perfectly fine. Bored it .030 over, new bearings on the old crank and rods, vortec heads, flat top pistons, Comp xtreme marine cam, and it rips now.

That's a good sounding outcome...maybe I'm on for some work.

I can't speak to an exact small block - but we have a 1976 - 165 - straight 6 mercruiser - that I swear is bullet proof. We have 660 hours on it - yes that is true and all I can say is that it doesn't burn a drop of oil - always starts and runs the Browning Mustang II around 40 mph. The boat trailer and for sure the motor are all original - we are trying to sell it since we purchased a larger boat -- and a more horsepower. One thing that we always did was use a 50/50 mixture of antifreeze during the winterization in the block - it think that that may have kept some of the rust down. For the past 2 years I've used that RV/Marine stuff and haven't had one bit of problems. In addition, I have been anal regarding the maintenance - tune up/plugs filters etc., and have always burn premium fuel with a lead additive.

good luck

3pointstar

I pulled my small block out of my '87 Chris Craft last year. It looked fine, had some scale but wouldn't have hesitated to re-use it. It was always in fresh or brackish (at worst) water. When I drained the block in the winter I would have to poke through some rust in the drain cocks also.
The reason I didn't use it was I went to a roller block.

It depends on the water as much as anything. Here is the great lakes the water is so soft that engines seem to last forever. I worked with a guy that loved old wooden Chris Crafts with small blocks, most of his boats were over 20 years old and still ran like new. I have a 98 and I pull the plugs every season and I have a small amount of scale in the plugs but that's it. I rebuilt it recently and did a full inspection and pulled all the freeze plugs and it was still in good condition.

We only run in salt-water, so you can basically double what we get. I've worked on engines as old as 30 years and they are still going strong...

for the price of a used block, i would always replace the block with one that spent it's life full of antifreeze. you are gonna bore it anyway...

Are you sure that scale isn't rusty residued sand. I am always getting sand out of my motor / manifolds. I don't think it is an issue in fresh water.

antifreeze is also corrosion inhibiter. they use it cuz fresh water by itself will corrode iron. that scale is layers of the inside of your block flaking off. for the couple hunnert bucks a 350 block costs, get a non-marine block.