Aft bilge pump lets water in?!

A check valve is the solution, be sure to get one that is full flow and non-corrosive, so it won't stick "open".

The Crealock designed Cabo 35 FB was their first model, not the 31 Express.

What survey do these boats actually have to pass and how often are they surveyed?

None. Never.

Now, there should be a purchase survey, but there are no requirements and while some insurer's would require one, other's would not on a boat this size.

I think that was a rhetorical statement - the point being that the proposed fix would not meet an ABYC or similarly standardized survey. But a lot of "home" repairs don't. I think many of us thought the OP was asking for the possible cause and a recognized solution. Nothing matters until it happens. He could put a cork back there if he wants, but I hope the insurance guy doesn't look back there.

Do not know what the fear of installing a check valve on the discharge side of a bilge pump is all about, it is a pretty common solution. All discharge lines should have some sort of loop or at least a positive angle from the overboard discharge point, prior to routing it to the bilge pump. Just do not have the check valve located below the waterline which ABYC does not recommend, but above - this is allowed by ABYC, so nothing to fear at survey or insurance reviews.

Readers have to understand the relationship with the cockpit deck to the waterline, not much room to get a proper vented loop above the waterline. Going through the cockpit deck is not an option . Maybe a loop, non-vented but with a check valve in this case. And when your are at full load /full gear on a small SF, its is not surprising to have a few discharge openings or even exhaust ports submerged. Full load on our old 46 Post usually had the cockpit scuppers nearly submerged, same with our 44 Pacifica, although that was with 900+ gallons of fuel onboard, but two extra large glassed in cockpit bait tanks. Usually wet sneakers in the transom corners while fishing at full load. Not saying it is the perfect design, but that stuff happens all the time.

To address the backflow - when you are trolling or at sub-planning speeds (transom still wet, not dry), there is enough of a vacuum (negative pressure) present at the transom to cause the sea water to attach to the vertical transom and inflow back thru the pump. Especially when you are fully loaded and have a swimplatform. But the fix is relatively easy in this case. Post a picture of the bilge pump set-up if you have a chance. Another little trick. Measure the waterline from the outside - from the chine up and the transom centerline up. Now mark the same waterline in your bilge with red tape or paint (don't forget to subtract for the hull thickness - about 3/4"). Now when you check your bilges (and do this in the engine room as well) you get a clear picture of hull penetrations vs. waterline.

Check valve - before a loop and be done with it, as the OP has correctly stated, there is plenty of redundancy of bilge pumps on this boat. If you wanted to be extra - extra redundant, you could install a hand operated bilge pump with a strainer at the absolute lowest point of the transom to keep her bone dry (manually) when you do your lazarette checks underway and at the dock.

Wire nuts are not necessarily a sign of poor maintenance. The USCG approves them for use on small passenger vessels in certain defined applications (CFR46-183.340 i).

The ABYC standards are not law, they are recommendations and "may" be followed by commercial vessels if desired but not following any particular one by an owner is not grounds for a toy boat surveyor to condemn the vessel.

I wouldn't put wire nuts on ANYTHING on a boat. I use heatshrink butt connectors on everything inside and out. The heatshrink helps prevent wires from pulling out.

It probably had either a loop above the waterline OR a checkvalve at some point in time. Someone probably replaced the bilge pump and buggered up the hose and cut it shorter or the check valve stuck and they simply took it out of the system. The boat needs either one ASAP and it's a quick/easy fix.

The ABYC standards are not law, they are recommendations and "may" be followed by commercial vessels if desired but not following any particular one by an owner is not grounds for a toy boat surveyor to condemn the vessel

Marmot

Lord knows it can be a fitful experience to engage you, but...are you stating that the ABYC standards for construction and repair are not a recognized measure for recreational boat construction and repair? Using your phase, can you give us a cite that would support that, or a cite that would permit a PVC ball valve to be installed below the water line and connected to the outside salt water source? Do you support this installation as an acceptable remedy? Can you give us a cite that would permit the use of wire nuts on any critical wire on a recreational boat? Nobody will complain if you use them to connect your FM radio, but even on a radio people will raise their eyebrows. I suspect even you.

As I said earlier, if the OP chooses to correct his problem with a cork, that is his choice. We were asked a question and I think we have all tried to provide sound constructive advice. Fortunately, he has upgraded his remedy to the proper installation of a check valve as a result of collective discussion and contribution.

Obviously, I really have no life after I close up Bodacious here in the NE....I am now donning my crash helmet and assuming the protective fetal position

I just stated the facts in order to debunk a common myth. What someone does on their own boat is their own business.

This year I have replaced 4 bilge pumps and 4 switches.
A few months ago the water in the bilge went past first lift switch and pump, then past the alarm lift switch and shorted out the junction box. The other bilge pumps on both port and starboard side kept the water below the engines. Luckily my boat is moored at my home and checked regular. I have now separated the original wiring so that the high water alarm is not in line with the bilge pump and also raised the junction box. The other failures were old switches in the engine room and lazzarette. It never surprises me what is found in the way a boat is wired, plumbed or fuelled. An example is a new UNIESSE 48 I purchased a few years ago. The fuel breathers were so badly designed and plumbed that when the tanks were full and I accelerated onto the plane, the diesel would discharge in bucket full overboard. Even after bringing it to the factories attention I was non chalantly told to keep less fuel or fix it myself.

There must be a lot of wrecks out there with dozens of bilge pumps that didn't do their job!

Try selling that to the insurance company when you have to have an insurance survey done every 3 years on most recreational boats.

As far as the ABYC world goes, even they use the word "recommendations" in their guide.You can choose to use their recommendations or do your own engineering, with the appropriate back-up documentation. There are many items that are not followed to the letter from ABYC in our industry, bonding/ground systems come to mind.

It is a good reference guide, along with other supporting documents from IEEE, SAE, NFPA and others. It helps to centralize focus on many common issues, especially for new builders and especially for surveyors. As far as the Law thing goes, who knows what a jury will ultimately decide? The courts do use the ABYC standards as legal references, but there is certainly room for engineering / technical interpretation. And other engineering / technical references. There is some risk in going away from common practice, but as I said before, you have to be able to back it up technically.

Inline PVC ball valves below the waterline - yes I have seem them, they are common on manifolds for the more complex bait tank systems out west, especially in the warmer clines of SoCal. But I would certainly use CPVC (grey) in-line valves for more piece of mind. Look at all the plastic non-reinforced thru-hulls that have been used above or near the waterline for decades during ABYC's widespread Industry use. Probably more boats have taken on water / sunk with a failed plastic thru-hulls, usually it shears at the flange after UV degradation, and even though it is above a waterline the overboard discharge now ends up in the bilge, fills the bilge with its discharge, the vessel lists, and then the sea water joins the party. But since they were above the waterline, they were ABYC compliant.

In the past, I knew of a few boat builders who were compliant with ABYC, and were certified by NMMA, but I would not recommend or spend my money on that brand, even though some of there models sold quite well. Always do your research with more than a single source.

Read the CFR. "(1) The connections must be made within an enclosure and the insulated cap of the connector must be secured to prevent loosening due to vibration; ..."

Recreational boat surveyors have no business opening any mechanical or electrical enclosure as part of an insurance survey. Few small boat surveyors are qualified or competent to determine electrical or mechanical condition in any event.

If wire nuts are used where they are not enclosed (visible in other words) then they are not in compliance with regulations and good practice in which case a surveyor may comment on their improper use.

The idea is that the use of wire nuts is "illegal" or indicative of poor maintenance is simply not true. It is just another boating myth that gets passed on and on and on.

It's not that it's illegal to do that. It's the fact that most insurance companies require recreational boats be maintained to abyc standards and surveyed every 3 years by an abyc accredited surveyor and it doesn't meet abyc standards and if it caused a fire would not be covered. Azimut used that practice for bilge pump connections 1' above the bilge water and they always failed.

But that's not to say that I haven't seen that practice. As well as some moron Italian builder that used a 220 volt breaker for 120 volt lights in the engine room and generator room, they ran 1 line to the engine room lights and another to the generator room lights. Then to top it off broke the connection on the light switch by using the neutral and not the line....so when I grabbed the fixture to change the bulb and the open cheesy Euro terminal strip inside the light hit the body, zapped the living daylights at out me.