Raw Water Cooled Inboard Problem - Need Advice

[archilles2]

Hey all,

My father in law just got his bowrider back from the mechanic after the inboard engine Hydro locked . Water got into the cylinders and in the oil, not once but TWICE! ( thanks Mercruiser )

First time we took it to the mechanic ( after about 20 outings since we purchased it 2nd hand ) he replaced the exhaust manifolds, telling us they had rusted out. Then after 3 outings the engine siezed AGAIN and water was found in the oil and cylinders on the right hand side.

We went off at the mechanic because he had already charged us $ 3500k He offered to do what he should of done and take the whole engine apart for examination and free repair. I don't know much about engines, but he said one of the pistons was stuck and rusty , he said he had to re bore the hole and clean out all the rust.

After hefty research i discovered that these modified car engines use RAW Water ( Sea water ) to cool them down and don't have a fresh water radiator ( like a car to cool them down ) , it is said that major engine parts need to be replaced every 5 or so years, costing $$$$$$ because of this system.

Why ? because polluted corrosive seawater is pumped directly into the engine to cool it down rather than having clean fresh water circulated around the engine like a car. As the boat sits between trips salt builds up along the walls and starts rusting out the engine.

FINALLY - WHAT SHOULD I DO ?

We love the boat, it's absolutely perfect except for the engine lol I'm not comfortable with the the cooling system and am almost sure this problem will occur once again.

I heard you can get a conversion to a fresh water cooling system , good idea?

Also, could anyone recommend a good additive as i plan to start flushing her in a bucket of water with a really good additive to rid all the salts and pollution.

This is a 3.0 l alpha one mercruiser and it's U.S made . I think these engines were really designed for fresh water use like the Mississippi not Botany Bay

Edited May 25, 2009 by archilles2

[BFB]

One of the problems with all inboard motors is that they are basically modified car motors, but then again, the same can be said for outboard motors.

Like all motors that operate with salt water they need to be flushed out properly or the salt will aid corrosion.

Unlike a car motor you can not just close off the cooling system and run a radiator instead as the problem becomes no cool air flowing through the radiator. I have seen used on race boats a system which uses a heat exchanger, i.e closed water system for the motor and heat is draw out by an additional unit which has the outside water flowing through. This system, to work properly requires two water pumps, one for the motor and one for the heat exchanger, to work correctly or a fast moving boat.

The majority of inboard motors use the outside water for cooling but it just needs to be flushed out everytime to ensure no salt water remains inside the water journals. The same goes for an outboard motor. The problem with this is the inboard motor is it is normally very loud when run out of the water as it uses the water to muffle the noise.

I think the answer to the problem is to ensure the motor has been correctly flushed everytime it has been used in salt water. To do this properly the motor needs to be running and up to operating temperature.

[pelican]

A lot for teh last 20 years are freshwater cooled and run a heat exchanger and I personally wouldn't own one that isn't . It can be difficult to fit in some small engine bays and to get a header tank high enough.

You can use a flush port on them either way.

When replacing manifolds I would have chosen to go for aftermarket stainless ones that last longer as well.

Sometimes with a unknown motor it is better to start fresh with a short block or even a fully dressed one and slot it in so all the unknown little things do not plague your enjoyment and safety.

I don't understand why your mechanic didn't notice a rusted bore when he did the exhaust as surely he would hav ecompression tested it and also if at all suspect lifted the head to make sure it wasn't also a dead gasket issue at the time he did that work. Most mercruiser guys use borescopes to quickly check these things as so often it is the case that one after the other water damage will have damaged parts of the motor and they will fail. Was the engine cooling system pressure tested after last rebuils?, does the motor show signs that it has been overheated in the past? Have water pump etc been changed? Are alarms on motor working? Bearings and rods are next.

Was the motor run regulary or has it been left to sit idle for 6 months?

Something isnt right 'here and a thorough inspection of past work and current motor are required to see just what is going on and a few questions.

Edited May 25, 2009 by pelican

[WANNAFISH]

In regarding the chemical to flush the motor, after every outing I use Salt Away with a special adaptor that connect to your flusher that will automatically feed thru ur motor. I use this one on my fishing gear aswell.

[archilles2]

Hey all,

Thanks for your great replies. We were not at all happy with the mechanic, i don't think he did anything you mentioned, they never ever got back to us when we would call them and would never explain the problem.

I think he took us for a ride because we didn't know anything about how these babies work. Well, let me tell you, you learn pretty quickly when you have to pay the $$

I doubt he used a boroscrope, or even did a compression test because after he replaced the exhaust manifolds the entire engine siezed again and only then was he forced to examine the all internals. We threatened to sue them because we paid $3500 to fix the problem - later to discover that only the exhaust manifolds were replaced.

Second time round he fixed everything - then again, only time will tell. He told us all of his work was covered by warranty and if anything happened to take it back. The only problem is i don't want to take it back to an idiot even if it's under warranty.

We have been using the boat almost every week since we purchased her in November so it's never really sat for more than 2 weeks.

We love our sea ray, and are thinking of getting stainless steel manifolds and installing a fresh water radiator.

We'll also try and inspect the risers every so often - but to be honest i don't want to have to do this all the time!

Edited May 25, 2009 by archilles2

[Flightmanager]

Archillies , do your self a big favour and have a talk to Craig from Huetts marine. He would be best able to advise you on what you need , and what it is going to cost . You can be 100% sure of the advice he will give.

Ross