CONTINUOUSWAVE

Give me advice on how to remove water from the foam of the Unibond hull of a 2009 SUPER SPORT 13 [which is assumed to be there due to poor performance and the static trim submerging the stern hull drain several inches below the waterline].


BACKSTORY
In Spring 2026 I bought a 2009 SUPER SPORT 13 with a Mercury 40-HP.This older is the first Boston Whaler boat I've owned in 25 years. Previously I have owned a c.1960 13-footer. Later I owned an OUTRAGE 18.

I have had the boat in the water a few weeks now, We're loving the Super Sport 13' and it's been fun with the family for cruising around and fishing inshore in Massachusetts. Having owned an old very and wet 13-footer, I was expecting some water in the hull of this 2009 boat.

There really seems to be a lot [of water in the hull in the foam of the Unibond hull] . The boat is sitting rather low in the water.

It will get onto plane, but even with just me (200-lbs adult man) aboard, the 40-HP engine needs to run at 4,500-RPM to maintain the boat on plane. When my wife and two small children are also aboard, the engine essentially has to run at full-throttle to maintain the boat on plane.

When at the dock in static trim with the 6-gallon on-deck fuel tank at FULL, the drain at the stern is completely submerged, and I have to leave that drain plugged continually.

We're going to enjoy the boat this season and I'd like to try to remove some of the water over the winter. I've seen a bunch of posts about people having both good and bad luck raising the bow and drilling a few small holes in the stern. I may be able to find a heated garage space to keep it and if people think this will make a big difference, I might try harder to find the space. Otherwise it will be in my yard.


ASIDE
I'm sorry if this is an annoying first post. I've been reading here and other places on the web for the past couple weeks and decided that the best thing is for me to start a new thread. I'm looking for some advice and it seems that there is a wealth of knowledge on this forum. Again, sorry if this is a question that gets asked all the time.

I would think the chance of a waterlogged 130 hull of that era is low. The modern 130 is much heavier than the classic 13-footer, if the engine is a modern four-stroke-poewr-cycle engine, it is also heavier than the two-stroke-power-cycle engines typically used on the classic 13-footerss.

Weight is a major factor on any boat and more so on a 13-foot boat. It's possible your engine is in need of a tuneup. Examine the propeller to ensure it has not been damaged. The propeller may not be the ideal size for your boating uses. Engine mounting height also affects performance. I recommend you post more information on your propeller model and engine mounting height to help members provide advice on those factors.

The threaded hull drain at the bottom of the transom should be in place when using the boat.

Finally, with you, your wife and two children, a full fuel tank and a cooler aboard don't expect your 13 to get on plane quickly or to go very fast. You may hear that raising the bow and drilling drain holes at the stern is not useful nor needed.

The 40-HP Mercury FourStroke engine was just fully serviced by a trusted marina. I don't know what propeller is on the engine, the the marina service guy said the propeller was good and didn't recommend changing it. I can get the propeller model and the engine mounting height. The engine came on the boat when new.

I understand that the transom drain plug should be in place when operating the boat but even with no one on board, the drain outlet sits completely underwater. Water just rushes in through the drain if the plug is removed. The boat will not self-bail. This is with a battery and 6-gallons of fuel and nothing else in the stern and nothing at all in the bow.

The boat is also just sitting lower in the water than other SUPER SPORT 13 boats I see. We tie-up right near one that has a Yamaha 40 and it is very noticeably higher in the water. Which is why I really think the hull has water in it.

The reported performance data does sound rather poor.

Apparently you have a tachometer for the engine. Check the recommended full-throttle engine RPM operating range. If the engine can accelerate into its recommend full-throttle engine speed, then the propeller is a proper fit for the boat.

As noted, small boats are very sensitive to added passenger weight. Going from one person to four will have a significant effect on performance with a small boat like a 13-footer.

The observation of the hull drain being submerged when the boat is in static trim will depend on who is aboard. Generally you would gauge this with no one on board. If the drain is still inches below the water line with no one aboard, then there is clearly too much weight in the stern. Some possible ways to reduce the down-by-the-stern trim are to moved the boat battery and fuel tank forward to amidship locations.

If the boat was sold with the Mercury 40-HP FourStroke, Boston Whaler seems to imply that the engine weight is not excessive.

The typical remedies for water that has accumulated in the foam of a Unibond hull are discussed in the FAQ in the REFERENCE section of the website. THe REFERENCE section contains many long-form articles about Boston Whaler boats. See

Q3: Is there water in a Unibond hull?
https://continuouswave.com/whaler/reference/FAQ/#Q3

Generally there is no easy or quick fix for a Unibond hull that is significantly overweight due to water in the foam.

In order for water to get into the interior of the Unibond hull, there must be some entry point. Common entry points are areas that are continually submerged on the exterior of the hull. The lower engine mounting bolts are one possible source. Any hull damage that penetrates the gel coat layer and exposes the laminate layer or the foam itself is also a possible entry point. In particular, hull bottom damage on a running surface of the hull can allow water to be forced into the interior of the hull as the boat is operated at high speeds. A very close visual inspection of the hull bottom may reveal any damage or repair--but only if there is no anti-fouling paint on the hull. A painted hull bottom can hide a lot of sins.

For boats left open and exposed to weather, water can accumulate in the cockpit. If there are any penetrations of the gel coat and laminate, such as screw fasteners not well sealed, water could also get into the foam via those paths. But typically such water entry would be localized.