Mystery Raw water leak

Spence

New Member
Aug 14, 2018
8
Spring Lake, Michigan
Boat Info
270 Sundancer 1995
Engines
454 Mercruiser w Bravo II
Hello,
1995 270DA 7.4L Bravo II. 1200 hours, I have been chasing several leaks this year, looking for other suggestions to find the last one. I have found leaks in the following areas and have corrected them.

Replaced Raw water pump
replaced Oil cooler
Replaced three hoses to and from Pump and Cooler
Replaced riser gaskets
re-Torqued exhaust manifolds

The boat will set in dock for a week without water in bilge. Left the outdrive up in trailer position, no water in Bilge, Left Shifter in gear, without running, for a couple hours, no leaks.

I have used baby powder to find traces of water without success. On average, I will get about 1/2 gallon per hour while under way, it does not increase or decrease depending on speed.
looking for another ideas to try in locating the last leak.
 
while the boat is underway the bow is higher than normal so any water that has pooled in the front or center of the boat will run back into the bilge....it may be possible you are getting rain/wash water pooling from a leaking porthole or if you have AC maybe a leaking condensate drip pan....then when you get on plane the water runs back to the bilge....

good luck....

cliff
 
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Welcome to CSR!

Does the water keep filling up the bilge if you run longer than a half hour? In other words, if you ran for 4 hours would you have 2 gallons of water in the bilge? What Cliff said is very possible. I would rule it out however, if the water stopped after a few hours of running on plane.

If it was rain water trapped elsewhere, then making it's way to the bilge once underway, It should subside after a few hours of running. If it continues at that rate for an extended period of time I would look elsewhere.

I had a boat that leaked only when underway, turned out to be the Y pipe lower gasket where it bolts to the transom assembly. Hard to see, almost impossible to get to without pulling the engine. I was able to get a piece of newspaper under the pipe and found it.
 
cliff,
Thanks for you quick response. when returning to the dock, all water gets removed from the bilge with a sponge, including under engine. Before we take it out again, I check for water. (my wife thinks I'm a little crazy) Unfortunately, I do not have A/C.
I have also have let the engine idle at dock for 20 minutes without getting water in the bilge.

I will revisit the transom being further under water while under way.
Thanks
 
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I image the boat needs to be underway to use the paper under Y-pipe idea, not an easy place to get to.
Thanks
 
No trailer, unfortunately I am at the mercer of the marina's cost sheets. If the y-pipe can be confirmed, I will be buying a trailer.

To answer the question.. run 4 hours and get 2 gallons in the bilge.. yes and no. I ran 6 hours between over two week nights, bilge pump ran and then I took out 3 gallons. This last weekend ran 6 hours, bilge did not run and when I looked, guessing 2 gallons, will bail out tonight (water below bilge sensor) and post
 
Do you only get water when the boat is running, or are you also getting water when it sits?

Do you only get water when the engine runs (at the dock at idle) or water with nothing running just sitting at the dock?

I have a 24' runabout, and I figured out that I would sometimes get water backwards through the bilge pump. My bilge outlet is too low to the water when the boat is full of people or if I'm running in waves (Lake Michigan), and there isn't a check valve in my bilge outlet hose. It wouldn't happen all the time - sometimes I could run for a full day and stay dry, but based on the angle of the boat and the size of the waves we were running through, sometimes we would get water.
 
Getting water in bilge only when underway at no wake and on plane. No water in bilge when idling at dock. I have checked the location of bilge outlets and are well above the water line at no wake and on plane.

Thanks for all the input, been chasing leaks all year and have fixed 4 and working on the fifth. I have found the most valuable information on these posts. Not sure what happened, last year was maybe getting 1/2 gallon over 15 hours.
 
I assume the 270 is basically a two part boat where the hull and deck are separate pieces....they are joined and sealed behind the rub rail....many people have experienced leaks in this joint....maybe while underway the bow is breaking the water and spraying it along the rub rail....if you had a leak in the hull/deck joint water could enter the boat and collect in the bilge....

cliff
 
Thanks for all the input, been chasing leaks all year and have fixed 4 and working on the fifth. I have found the most valuable information on these posts. Not sure what happened, last year was maybe getting 1/2 gallon over 15 hours.

That leads me to think something is rusting out slowly and the hole is getting bigger, allowing more water through.
 
That leads me to think something is rusting out slowly and the hole is getting bigger, allowing more water through.


or a leak in the hull/deck joint is getting larger over tme.....

cliff
 
Check the steering pin... only leaks when there is pressure and steering action. Common failure.
 
I'm surprised no one has mentioned bellows, and slipping the boat with the I/O in the trailer position. It's been quite a few years since I've slipped an outdrive boat on Spring Lake. Back in the day we always kept the drives trimmed all the way down to prevent damage to them from wakes. Also, there was concern the bellows would take a set that could lead to cracks in the rubber over time. With some boats Muskrats were a problem. On of my neighbors had a boat sink when a Muskrat chewed a hole in the bellows on a drive that was left in the upright position.
 
Any chance it is from your fresh water system? I have been chasing a leak for about a month. Just knew it was from one of the motors. Turns out it was from my mixing valve on the hot water heater. Anytime the hot water was turned on (using the shower on the stern often) it leaked out of the top of the valve. Just replaced it today. Still dry so far. Will see how things do this weekend.
 
Took out about between 3 to 4 gallons, Then tried to get paper under the Y-Pipe trick and was going start it up. After assuming the position, I got my hand under the Y-pipe and started feeling around and found a loose nut that felt like was in front of the Y-Pipe. I got a open end wrench on it gave it a few turns, I felt it tightening, but didn't tighten to much, I am concerned exactly what is getting tightened, any insight is welcome.
 
After sitting at dock, in the water, for four days, no water in bilge. Loosened the clamps on the top of the Y-Pipe and tighten the lower nut, the other lower nut was tight. Checked all clamps again and spread more powder near the connections. Went out for 5 hours, wake, fast wake and on plane, enjoyed the day. Got back and opened the hatch, bailed out about 2.5 gallons. no fresh water traces.
Cliff,
I will start digging into the joint leaks, any suggestions on where to start?
 
After sitting at dock, in the water, for four days, no water in bilge. Loosened the clamps on the top of the Y-Pipe and tighten the lower nut, the other lower nut was tight. Checked all clamps again and spread more powder near the connections. Went out for 5 hours, wake, fast wake and on plane, enjoyed the day. Got back and opened the hatch, bailed out about 2.5 gallons. no fresh water traces.
Cliff,
I will start digging into the joint leaks, any suggestions on where to start?

I have not done the job of re-sealing the joint but many members have....hopefully one of them can offer some guidance....

good luck....
cliff
 
I would suggest checking the structural integrity of the wood cored transom. The best way I know is to bounce on the outdrive when the boat is on a trailer or on blocks. The fact that the leak only occurs when underway makes me suspicious. Could be leaking where the outdrive mounts to the transom.
 

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