Source of leak on back of Maxum 46’ SCB help

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CherylZ

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Aug 9, 2025
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37461
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Hi there we have owned this boat almost ten years and have been unable to detect source of leak despite multiple surveys and repairs.

Wondering if anyone knows where the leak on one side of boat is coming from. It’s linked to when we run the engine higher throttle and thinking it’s coming from swim platform somewhere or possibly rudder seals. We replaced shaft seals.

Mostly water ingress is minimal but it’s still there. But today was a good foot of water under the generator and into the engine area. Bilge was working. We throttled down.

Any others have this problem?
 
Any chance you, or someone else, can observe &/or video the area(s) while under high throttle?
 
Yeah, you're going to have to get down there and watch. Could be several areas: saft seals; engine hoses; vents letting water in; etc.
 
Just on the starboard side then it spilled into the engine area. One of the bilge pumps had a blockage in the tube we fixed to help get water out but we went low throttle all the way to port. When we get home we do a haul out and will also have an engine guy go out with us under high throttle to see if he knows where it’s coming from.
 
Exhaust would be my primary suspect. First thing I would do is run each engine in neutral at higher RPM… 1700/1800 and look around the engine and especially the exhaust hoses. Follow them all the way. They can degrade over time and you could also have a broken clamp. Also if you have a combination of hose and fiberglass tubes, you could have a crack where the hoses are clanked to the tubes / mufflers

I doubt it s the swim platform brackets / bolts. On plane there is less pressure in that area.
 
Thanks so much! We did notice when we went off plane and the throttled down water decreased.
 
PascalG said:
Exhaust would be my primary suspect. First thing I would do is run each engine in neutral at higher RPM… 1700/1800 and look around the engine and especially the exhaust hoses. Follow them all the way. They can degrade over time and you could also have a broken clamp. Also if you have a combination of hose and fiberglass tubes, you could have a crack where the hoses are clanked to the tubes / mufflers

I doubt it s the swim platform brackets / bolts. On plane there is less pressure in that area.
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I had the exhaust hose problem years back on my Luhrs. Same symptoms of only getting water in at higher RPMs, which is tough to monitor with the Luhrs design. There was a small crack in a hose where it made a rather sharp bend.
 
Thanks so much Bob! Will check that out. Exhaust was another area we were thinking. We also wondered if it might be where the rudders attach (seals) and of course you can’t see that directly, covered by a metal plate that must be removed.

We plan a haul out and will bring in an engine expert.

Would sure be nice if the engine designs were a little more DIY friendly. Plus you gotta be small to squeeze into some of those areas…
 
i really doubt it s the rudder seals. If it was it would be leaking with the boat at rest in the slip

Probably best to inspect the exhaust system in the water and start with the engines, one at a time, running in neutral at the cruise RPM you get leakage. One way to spot leaks is to use blue shop towel laid under the exhaust or suspect source of leak. It s also great to wrap around hoses and fittings. Any leak will cause the shop towel to turn darker.
 
What about cruising on just one engine at a time. If it was engine related it would at least narrow the search a bit. If you get water in no matter which engine you are cruising on then that rules out both. Just a thought.
 
PascalG said:
i really doubt it s the rudder seals. If it was it would be leaking with the boat at rest in the slip

Probably best to inspect the exhaust system in the water and start with the engines, one at a time, running in neutral at the cruise RPM you get leakage. One way to spot leaks is to use blue shop towel laid under the exhaust or suspect source of leak. It s also great to wrap around hoses and fittings. Any leak will cause the shop towel to turn darker.
Click to expand...
We isolated the problem. Two of them. Shaft seals that we just replaced two summers ago leaking. And a small leak coming from swim platform in a spot that someone before us had fixed in the past. But the majority of water coming in from the new shat seals at higher knot speed. 2000 rpm.
 
CherylZ said:
Hi there we have owned this boat almost ten years and have been unable to detect source of leak despite multiple surveys and repairs.

Wondering if anyone knows where the leak on one side of boat is coming from. It’s linked to when we run the engine higher throttle and thinking it’s coming from swim platform somewhere or possibly rudder seals. We replaced shaft seals.

Mostly water ingress is minimal but it’s still there. But today was a good foot of water under the generator and into the engine area. Bilge was working. We throttled down.

Any others have this problem?
Click to expand...
We isolated the problem. Two of them. Shaft seals that we just replaced two summers ago leaking. And a small leak coming from swim platform in a spot that someone before us had fixed in the past. But the majority of water coming in from the new shat seals at higher knot speed. 2000 rpm.
 
CherylZ said:
We isolated the problem. Two of them. Shaft seals that we just replaced two summers ago leaking. And a small leak coming from swim platform in a spot that someone before us had fixed in the past. But the majority of water coming in from the new shat seals at higher knot speed. 2000 rpm.
Click to expand...
What seals did you use?
 
Supposedly the newest ones that were supposed to be drip less. My partner looked up manufacturer and apparently they frequently need pressure plate adjustments. Yet another expensive haul out.
 
CherylZ said:
Supposedly the newest ones that were supposed to be drip less. My partner looked up manufacturer and apparently they frequently need pressure plate adjustments. Yet another expensive haul out.
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Give is the type and help. If it’s a PSS mechanical seal, which it sounds like, they are easily adjusted in the water.
 
All drip less shaft seals can be adjusted in water and in some case they can even be replaced in water as well depending on the type.

What brand are they?

PSS sometimes can be fixed by cleaning the face seal and adjusting the rubber boot.

Tides Marine seals can also be replaced in water.

on an older boat make sure the surface of the shafts isn’t scored. If it is, the new seal will not change anything and the shaft will have to come out to repair the surface. Just went thru this on the 110 Lazzara I run
 
PascalG said:
All drip less shaft seals can be adjusted in water and in some case they can even be replaced in water as well depending on the type.

What brand are they?

PSS sometimes can be fixed by cleaning the face seal and adjusting the rubber boot.

Tides Marine seals can also be replaced in water.

on an older boat make sure the surface of the shafts isn’t scored. If it is, the new seal will not change anything and the shaft will have to come out to repair the surface. Just went thru this on the 110 Lazzara I run
Click to expand...
PSS is brand name.
 
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