OFFICIAL 390/40 Motor Yacht Thread

I have not kept good notes on my rpm to speed.
So, about 2700-2800rpm for 10-13mph and 3200-3300 for 17-19mph.
I assume the bottom of boat is pretty clean.
 
Joel, the void goes quite a ways forward but luckily stops just before the bow thruster. It took several shop vac fills before it was empty. Not sure but some rough guess calculations are that it holds at least 50 gallons which would be 400 pounds or so.

My yard's biggest concern was that the water was coming from the outside and yours probably isn't either but probably needs to be checked out. Even if yours is under pressure I don't think you need to be worried about sinking from opening it up although it is alarming to have a geyser in the bilge. I have had older boats with speed paddle wheels through-hulls had to be removed and cleaned just about every week so I got used to it.

I had thought my problem was a one-off but I'm wondering if it is a class problem. It seems the void is probably not well sealed somewhere.

I am new to this forum but really enjoying reading the posts. I see the access panel into the void in below the isolation transformer and it is exactly what I did. My issue is that I still get water and am not sure where it is coming from. What are the most likely sources that I check?
 
Folks I'm going to look at a 87 39' today. IF this is something I jump onto I'd be moving up from my 30'. I'm not completely sold on making this move.

She has twin Crusaders with less than 200hrs FWC. Her cabin and cockpit have been redone and full canvas. She is still in the water so I won't be able to look at her hull and running gear. GenSet appears to be shot. Owner says he will adjust the price accordingly

Can you 39 folks give me a idea as to any other big issues to look for?
 
I am new to this forum but really enjoying reading the posts. I see the access panel into the void in below the isolation transformer and it is exactly what I did. My issue is that I still get water and am not sure where it is coming from. What are the most likely sources that I check?
What color is the water if any? If it's reddish, the water is coming from a void and leaking out into the bilge. Then the question is how is it getting into the void? Are you in fresh or salt water? If salt, the first step would be to try to figure out if the leakage is salt. I just taste it and that seems gross these days, but I don't know any other way to test except some kind of analysis. Anyway, the most likely fresh sources are the numerous potable water system connections in the space, including the manifold, the water heater and the washer if you have one. My source was a loose fitting on the water heater. Fresh could also be rainwater; a gap in the caulking between the hull and the deck joint would not be unusual in boats of our age. Sorry to not be more definitive but leaks can be very frustrating and hard to find. There are stories of owners chasing them for years.
 
Folks I'm going to look at a 87 39' today. IF this is something I jump onto I'd be moving up from my 30'. I'm not completely sold on making this move.

She has twin Crusaders with less than 200hrs FWC. Her cabin and cockpit have been redone and full canvas. She is still in the water so I won't be able to look at her hull and running gear. GenSet appears to be shot. Owner says he will adjust the price accordingly

Can you 39 folks give me a idea as to any other big issues to look for?
dwna1a, this thread is about the 390/40 Motor Yacht which is a different boat only made later than what you are looking at. I took a quick look and couldn't find a thread dedicated to that kind of boat, at least with posts in the last year or so. Hopefully someone with knowledge of that boat will see this but you might want to just start a new thread with some details of year/model/engine in the subject line. If things go well, maybe you can start a dedicated thread for your model. Best of luck in the hunt.
 
What color is the water if any? If it's reddish, the water is coming from a void and leaking out into the bilge. Then the question is how is it getting into the void? Are you in fresh or salt water? If salt, the first step would be to try to figure out if the leakage is salt. I just taste it and that seems gross these days, but I don't know any other way to test except some kind of analysis. Anyway, the most likely fresh sources are the numerous potable water system connections in the space, including the manifold, the water heater and the washer if you have one. My source was a loose fitting on the water heater. Fresh could also be rainwater; a gap in the caulking between the hull and the deck joint would not be unusual in boats of our age. Sorry to not be more definitive but leaks can be very frustrating and hard to find. There are stories of owners chasing them for years.
I am in fresh water so the taste test will not help. At times it seems to have does brown dirt in the water which likely means
What color is the water if any? If it's reddish, the water is coming from a void and leaking out into the bilge. Then the question is how is it getting into the void? Are you in fresh or salt water? If salt, the first step would be to try to figure out if the leakage is salt. I just taste it and that seems gross these days, but I don't know any other way to test except some kind of analysis. Anyway, the most likely fresh sources are the numerous potable water system connections in the space, including the manifold, the water heater and the washer if you have one. My source was a loose fitting on the water heater. Fresh could also be rainwater; a gap in the caulking between the hull and the deck joint would not be unusual in boats of our age. Sorry to not be more definitive but leaks can be very frustrating and hard to find. There are stories of owners chasing them for years.

At times it has brown dirt in the water which leads me to believe it is river water. I don’t believe it is potable water, I had lots of those leaks and have fixed them with new Pex fittings and crimp clamps. The leak is into the void below the steps where I cut an access hole. I thought water might enter this via the anchor locker but checked and there is no sign of a crack under the anchor rode. I can’t figure out how water can get into this area. It does run directly under the bow thruster tube so that might be worth examining when the boat is pulled but the survey guys looked closely at the area since previous owner reported the issue which was presumed to be a bow thruster seal which was replaced. I am stumped and appreciate your comments. With this void originally sealed it is a mystery on how water gets in.
 
I am in fresh water so the taste test will not help. At times it seems to have does brown dirt in the water which likely means


At times it has brown dirt in the water which leads me to believe it is river water. I don’t believe it is potable water, I had lots of those leaks and have fixed them with new Pex fittings and crimp clamps. The leak is into the void below the steps where I cut an access hole. I thought water might enter this via the anchor locker but checked and there is no sign of a crack under the anchor rode. I can’t figure out how water can get into this area. It does run directly under the bow thruster tube so that might be worth examining when the boat is pulled but the survey guys looked closely at the area since previous owner reported the issue which was presumed to be a bow thruster seal which was replaced. I am stumped and appreciate your comments. With this void originally sealed it is a mystery on how water gets in.
Could it be the seal on the depth finder transponder in bilge?
 
I am in fresh water so the taste test will not help. At times it seems to have does brown dirt in the water which likely means


At times it has brown dirt in the water which leads me to believe it is river water. I don’t believe it is potable water, I had lots of those leaks and have fixed them with new Pex fittings and crimp clamps. The leak is into the void below the steps where I cut an access hole. I thought water might enter this via the anchor locker but checked and there is no sign of a crack under the anchor rode. I can’t figure out how water can get into this area. It does run directly under the bow thruster tube so that might be worth examining when the boat is pulled but the survey guys looked closely at the area since previous owner reported the issue which was presumed to be a bow thruster seal which was replaced. I am stumped and appreciate your comments. With this void originally sealed it is a mystery on how water gets in.
Although the void appears to be sealed from what can be seen from above, it's apparently pretty open from the sides, at least on mine.
There is a non-destructive test your yard should be able to do to check for external leaks. When my filled void was discovered, they did a quick pull to perform the test. I don't know the details but the major worry was about leakage around the nearby thruster tunnel. The cost wasn't much more than the price for the haulout.
Have you noticed any pattern around when water shows up such as after periods of rain or underway periods? You might also try having someone watch the void while another person takes a hose and sprays the topsides, especially around the rub rails.
 
One more time corrected. Changed the looks.
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When utilizing the shore water to the adapter on the swim platform do you need to switch anything inside to run off of shorewater? Or will it do it automatically?
 
When utilizing the shore water to the adapter on the swim platform do you need to switch anything inside to run off of shorewater? Or will it do it automatically?
Nope, just turn it on and it should work. It's not a good idea to have the potable water pump from the onboard tank on at the same time but there is a check valve to prevent contention between the two water sources.
 
Could it be the seal on the depth finder transponder in bilge?
Good thought, but the water is not coming into the forward bilge area. Water is coming into the closed void that you step on at the bottom of the steps....... I opened it up with a round access door after I saw water seeping through screw holes. I completely drained the void last week and have since operated bow thruster, washed the boat and did a slow speed cruise for an hour, used the anchor and washed it as I was pulling it out and the void is bone dry. I am convinced it happens when cruising where water is washing up the hull. I will look for a rub rail leak having someone spray it while I am watching for water. Leaks are frustrating but now that I have eliminated many of what I believed were the causes I hope to find it this week.
 
I assume the bottom of boat is pretty clean.

The bottom is ok. We will have it pulled and repainted this summer.

On our trip this past weekend, I was running 3520 rpm for 17 mph (SOG), with trim tabs full bow down for about 3 hours. We had a 8kt winds on the bow, running against the tide, started with full fuel and somewhere between 3/4-1/2 tank of water. I think I can get to 19 mph (SOG) without the bow wind and tide. Amount of water in the tank seems to make a big difference.
 
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The bottom is ok. We will have it pulled and repainted this summer.

On our trip this past weekend, I was running 3520 rpm for 17 mph (SOG), with trim tabs full bow down for about 3 hours. We had a 8kt winds on the bow, running against the tide, started with full fuel and somewhere between 3/4-1/2 tank of water. I think I can get to 19 mph (SOG) without the bow wind and tide. Amount of water in the tank seems to make a big difference.
That’s pretty good. What was your fuel
Burn?
 
I think thats pretty good.

I thought I might get closer to 20mph at 3500 rpm. And with less mass, and a better sea state I might. I can see that the 390MY with gas engines is very weight sensitive. I had planned to travel with full water from home port. Now I will change that and travel with closer to 1/4 tank and fill accordingly when I stop. We will also make sure that black water tank is empty during travel as well.
 
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