Boat engine question

[hancoveguy]

Okay, where are all my mechanical people out there? Take a stab at this one. I will post more diagnostic/trouble shooting info as I get it.

Just bought a 98 Wellcraft Eclipse 2400 SS. The 7.4 liter v8 appears to have some issues. The hour meter says 150 hours or so. The motor APPEARS clean and intact. My mechanic tells me that the front, down tubes on the exhaust manifolds have some cracking and peeling paint as if it was run really really hot at some point. There was a slice of bread sized burned rubber flap thing found inside the manifold. He said the plugs were fine and the motor fired right up and seems to run okay but he wants to test it under a load. I think he suspects some circulation problems too. The boat sat for 3 years or so in a rack and as far as we know it was winterized properly by a marina. I have the utmost faith in my mechanic but would be curious to hear ideas or experiences anyone here has had that resemble this situation.

Last thought, any suggestions for a place to sea trial the boat at speed in the Merrimack Valley in Mass. I'd hate to drag it up to the lake for what could turn out to be a 10 minute sea trial.

Thanks
HCG

[Airwaves]

I have no idea about the mechanics of this question, but the only places to run the boat hard in the Merrimack Valley are in Lowell on the Merrimack River (local knowledge of rocks required).

Your better bet in the Merrimack Valley is to drag her to the mouth of the Merrimack and head to the Isle of Shoals and back a few times. That will blow the cobwebs out!

[rider]

depending on the water conditions it was run in, also could have sand in it may be? Only indicator of that would be a scratched up hull and the lower unit missing paint but still be intact. You check out the raw water pump? Might as well replace it. If you replace it and it still overheats at WOT, it might need a new circulation pump on the front of the block. With the engine running on a hose, you should be able to see whats up with it without having to put it in the water. Down tubes rust and flake all the time, if its white though, you might have a problem with the water injection system on the risers. Those are most likely rusted either off or shut and will have to be replaced.

[Baja Guy]

That flap belongs in the exhaust and it keeps water from backing into the engine during rapid decelleration and backing up. When it is burned up the engine has run very hot.
It can be repairable. You need a boat tech who can assess & correct the situation.

[BroadHopper]

Originally Posted by Baja Guy

That flap belongs in the exhaust and it keeps water from backing into the engine during rapid decelleration and backing up. When it is burned up the engine has run very hot.
It can be repairable. You need a boat tech who can assess & correct the situation.

This is true. As for the rest of the engine, a multitude of things came up in my head. I will have a very reliable engine mechanic go over the whole engine, compression check etc. If the engine was running hot, I would check the thermostat and have the cooling system back flushed. If the engine was drained rather the antifreeze, you may have tons of rust scales to deal with. As for the risers, cast iron risers do not last long in an open system, especially in salt water environment. When the engine is warming up, check to see if both risers are warming up at the same time. If one is cold and the other is hot, shut the engine down and investigate.

One could write a book on this subject. A good mechanic makes sense.

[Dave R]

I have the same engine in my boat.

The exhaust flappers are a wear item. They are very cheap and very easy to change. You need to pull the elbows off the manifolds to change them, so have new gaskets (again, cheap) handy and make sure you get bring the engine serial number when you buy the Mercruiser (I assume it's a merc...) gaskets. The right gaskets for your engine likely have restrictor holes to create a bit of cooling system back pressure. A lot of people use the wrong gaskets in this application.

While the elbows are off, you'll have a perfect opportunity to check the elbows and manifolds for excessive corrosion. If you need new manifolds and risers, OEM are the best. GLM parts are OK if you know someone with a machine shop that can mill the gasket mating surfaces flat.

I agree that it's likely been run hot, but I would not sweat it. If you are serious about buying the boat, replace the impeller before you head out on the water. While the pump is off the block for impeller replacement, disconnect the hose that goes to the oil cooler from the thermostat housing and back flush the oil cooler, fuel cooler, and power steering cooler. Odds are good there's bits of failed impeller in them. It's a simple procedure that adds 3 minutes to the impeller job.

Compression on a 150 hour 7.4 should be around 140 to 150 PSI. However, if it's checked cold, it'll likely be way off. If it is off, check again after the test run.

That engine should run to 4500-4600 RPM at WOT

Good luck!

[Steveo]

Damn, I love this kind of talk!!!

[hancoveguy]

Thanks to all, this is the kind of feedback I was looking for. Its a Volvo and we are changing the impeller and circulator pump today before we run it tomorrow. As far as I know it has always been a fresh water boat.

Keep the ideas coming and I will post any updates I get.

thanks
HCG

My biggest fear is that it needs a motor, we are not nearly there yet but I am concerned...

[Dave R]

Volvo stopped recommedning the exhaust flapper is in most applications a few years ago. You may want to try running without them. Just be careful not to come off-plane rapidly or water can back up into the exhaust manifolds and then flow down into the cylinders that have open exhaust valves, when you shut it off. If you have no choice but to come off-plane rapidly, DO NOT forget to put the engine in neutral and rev it a few times to blow the water out, before you shut it off.

[Sman]

Even if it is fresh water only, eventually the water jackets in the cast iron manifolds do get junked up with rust and can impede flow. I had this problem with one. When I had the water hooked up to the lower unit running it on the trailer, there was a significantly lighter "spitting" of water out of one of my stainless pipes, I also noticed a slight discoloration in that one pipe, (getting hot). I changed out the manifold, cost about 240, got it from a dealer in MA, came with gaskets, did it myself, problem was solved. I was told I should have just done both but did not, oddly enough I have no issues with the older one, (yet). Just one possibility and my boat at the time was 25 years old, lake winni only and had less than 300 hrs, mercruiser.

[BroadHopper]

2 years ago, I purchased a 1988 Formula F-223 LS with 454 Magnum from a marina in VA. It was pretty much abandoned on a trailer and stored indoors for seven years. The Potomac Marina sold it for what was owed for storage. It was in perfect shape for a 20 year old boat. The boat was put away properly and all it needed was fresh batteries. I had a written agreement with the marina that if it doesn't pass survey and my local mechanic approval, I can get my money back. I bought it for less than a third of the book value with 367 hrs on the clock.

Dave's Motorboat Shop surveyed the boat, checked out the motor and took it for a test drive. They were pleased with the motor and agreed that it was well taken care of. To be safe, they replace the impeller and doublecheck all the rubber boots in case of 'dry rot'.

Good Luck with your purchase.

[hancoveguy]

Okay, went for a quick sea trial today on the Merrimack. Both risers seemed to heat evenly, neither got real hot but warm to the touch in cold water. Boat temp went up slow. oil pressure seemed pretty high if the guage is right (75 ish) at wot. My mechanic babied it for quite some time before we throttled it up. Very smooth, got up on plane much faster than my old express cruiser, which was a treat. We shut it down after running it for 30 minutes or so and restarted it looking for hydrolock and it fired right back up several times.

Overall very pleased. Only glitch was that the exhaust tubes in the back on both sides were leaking a bit. Not weeping but not pouring either. Mechanic will take it apart and diagnose it and we'll go from there.

Again, always looking for thoughts and experiences...

HCG

[robmac]

The one thing I do to try and prevent any rust build up in the coolant passeges is,when winterizing I run a half of a gallon of CLR through the cooling system using a set of ears and very large funnel. I am amazed at the crud that comes out but knock on wood never had an issue with buildup.

[Sman]

The one thing I do to try and prevent any rust build up in the coolant passeges is,when winterizing I run a half of a gallon of CLR through the cooling system using a set of ears and very large funnel. I am amazed at the crud that comes out but knock on wood never had an issue with buildup.

Interesting, can you elaborate a bit on what you do, where you put it in, where is is coming out. I winterize the engine and use a set of ears on the lower to keep water going through, but where are you putting in the CLR and I am taking it that it is the Calcium/Lime/Rust remover product...

thanks

[robmac]

You are correct,Calcium,Lime and Rust remover. I first bring the engine to temp running off hose, Then remove hose and attach short hose connected to large funnel restart until all of the CLR has been picked up and shut off. Let sit for 10-15 minutes then flush out with hose. Afterwards run anti freeze throughout and get it all set for winter. I've been doing it since 2000 when I lived full time in FL. and inside of manifolds and risers and clean as can be. The solution exits my boat through the transom exhaust and it is nasty.