Official 390 E.C. Thread

Hi everyone! I'm a brand new owner of a 1988 teal 390 EC with 340 hp 7.4's. As far as I can tell, she's 100% original. The last owner took good care of her. You could eat off the bilge. She's a fresh water boat. We took her out for the first time yesterday and I've been browsing this thread a bit. I've got questions... :)

When we took her out, I tried to get her on plane. No go. Engines are smooth, sound good, and are of equal power. Planes bow down, WOT, and she got up to 21.7 knots and wouldn't climb out. WOT RPM on both engines was 3500, no faster with the throttles pinned. She has the original tabs, and 4 blade props, I don't know the dimensions. 1.88 Velvet Drives. I am at a loss.

The water tank was full and 1/2 a tank of gas on both sides. Bilge has been close to dry. Water tank area has been dry, until I ran the AC... I haven't seen any water in the water tank bilge until I ran the AC, and slowed down from the 21 kts. I don't think the watet tank itself is leaking... yet...

Does this mean I have the dreaded wet foam problem? Too much weight due to this water in the foam causing the boat not to climb out?

I also see all the pics of the water tank removal and foam removal. Is there a separate panel that is removable under the rug, or are you guys cutting the cabin floor above the stringers to access the tank?

How are you removing the foam without cutting the whole sub floor under the tank out? How far forward does the dreaded foam go? Is it always doom for the stringers?
 
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check to see how low it sets in the water at the dock. If water is up to the exhaust outlets there is a problem. Also if the original carpet is in the galley tank has never been repaired.
 
Thanks for the replies!

I definitely have water in the center storage, up where the tank is, but I only really saw it after running the ac. I'll take pics next time I get up there.

She sets in the water with the exhaust ports up about 2-3 inches from the surface. I definitely think it's the original carpet in the galley. I was kind of excited about that originally... oh well...

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Looking at the space the mufflers take up in the engine compartment. Thought here is why not eliminate them
. Sure the boat would be loader running but to the good there would be aot more room in the engine compartment.
 
Looking at the space the mufflers take up in the engine compartment. Thought here is why not eliminate them
. Sure the boat would be loader running but to the good there would be aot more room in the engine compartment.

How would you use the space and how would you get access to it. You would have to save them to reinstall for resale anyway. They would take up space in your garage/basement/storage unit. Not to mention your dockmates wouldn't appreciate the noise.
 
In asking this question. Looking at the muffler space it takes up a inline muffler can be installed that would open up a larger working area to be able to get to the other side of the motor to work on it. This is mostly the space needed for the starboard side. There are boats made with in line muffler. Such as Wellcraft and Regal boats. Looking at the system on a 1990 39 Express it would not take much to switch it over.
 
Finally got around to replacing the galley faucet assembly tried to rebuild it with no results. All the fittings were frozen and not going to loosen. What I found out to pass on; the sink is mounted to the counter top with wing nuts. Still a bit of a task to complete.
 
You may need the aqualift mufflers because the motors might be mounted to low to the water line, to meet the correct amount of drop and angle that the exhaust system should have according to mercruiser.
 
You may need the aqualift mufflers because the motors might be mounted to low to the water line, to meet the correct amount of drop and angle that the exhaust system should have according to mercruiser.
Not a bad thought although boats made by Fountain, Cigarette, Donzi, all the motors are set lower then the exhaust outlet. Don't necessarily see it to be a possible problem.
 
Not much luck needed I built street machines, street rods from the ground up. Molded fiberglass parts. Repaired holes in boats. Welded stainless and all other metals. I have a complete shop in my pole barn to do about any project needing done. So I'm contemplating running duels on each side there are already two fiberglass exhaust tubes coming off the motors leading to the muffler. Make a wax plug the design needed to connect the fiberglass exhaust tubes to the two mufflers. Fiberglass the wax to the thickness needed with fire retardant fiberglass then melt the wax inside. All that is needed is the mufflers.
 
As far as noise. There are 2 Regals in the marina I dock at and they are lowed when they are running. I have to believe the boat would run better without the restriction of the uplift mufflers. There is one point to bring up. My wife says I cant just leave things alone I have to modify them. I was looking at her caravan telling her what all I could do to customize it. That ended quickly. LOL.
 
When I repowered years ago I removed the waterlift mufflers. I ordered the new engines with riser spacers to raise the exhaust starting point then installed flow through mufflers. I had to cut the exhaust tubing inside the hull boat and glass in an angle to match the new straight exhaust design. Not an easy job and really didn't save much space once the new mufflers were installed.
 
Melifluonze

Your exhaust ports are the about right amount above the water. I would not look at overloading as the cause of your not planing off. That said, you should check the area around the water tank for water accumulation often. Sea Ray does not put a bilge pump forward of the engine room bulkhead so any water will accumulate around the tank since it has no where to go. This will eventually rot out the stringers. Been there.
 
need to rebulid my sea star cylinder looking for a kit #KS06 anf one knows were i can purchase one
 

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