1985 SUPER SPORT 15 Static Trim

[davidB01]

Q1: is the boat waterline at rest (static trim) of my 1985 SUPER SPORT 15 (as described below in the long narrative) typical of this model based on your own experiences with this model?

Q2: If not typical of your experience, what was your experience?

NARRATIVE OF THE LOCATION OF THE DRAINS AND AMOUNT OF WATER IN THE BOAT
[The following] observations are for at rest in the Lake on a calm morning with respect to height of the boat relative to the water, and these have seemed to stay constant since Spring launch.

AT REST WITH DRAIN PLUGGED AND NO WATER IN COCKPIT
The stern quarters at the transom are below the waterline by 1.5-inches. Lake water laps into the bottom of the two drains in the [engine] spashwell.

AT REST WITH DRAIN UNPLUGGED
About 1.5-inches of water collects on the cockpit deck in the stern due to overflow of the sump. Water comes up just over the two pads to port and starboard of the [engine] spash well,. The water comes up just behind the rear storage compartment of the [helm seat]. View from outside the boat, the boat appears to settle into the Lake about another half-inch deeper. In the engine splash well there is water in the two depressions that lead to the drains and the drain outlets on the transom are half-submerged

Q3: is there a concern about leaving the plug out of the boat during Summer for about five months?


USE BY FAMILY
This Summer is the first full summer with the 1985 SUPER SPORT 15 at the Lake. I am enjoying it immensely. Two family members are now comfortable enough to take it out on their own, and that outcome is a big win and one of the primary reasons why we got this boat.

REASON FOR THE QUESTIONS
I am looking for some advice on controlling water inside the boat.

BACKGROUND ON PRIOR USE OF THIS PARTICULAR SUPER SPORT 15 BY PREVIOUS OWNER
This 1985 SUPER SPORT 15 has had about 30 weeks of use in its life until I bought it last year, with an estimated 150- hours of use. It sat in a garage and was not used last 10 years.

USE IN 2024
I launched the 1985 SUPER SPORT 15 on Lake Winnipesaukee in New Hampshire in the Spring of 2024. The original [Johnson] 70-HP engine gave me problems in the Summer of 2024.

NEW ENGINE WEIGHT COMPARED TO OLD ENGINE
In the Fall of 2024 I re-powered the 1985 SUPER SPORT 15 with a Tohatsu 60-HP, model T60, which is actually somewhat lighter than the original Johnson 70-HP engine.

USE IN 2025
In early May 2025 I launched the boat. It is tied alongside a dock with whips. This has been in the situation for [the time since early May 2025 to the date of this post].

USING THE BOAT BY TRAILER LAUNCHING
[Use of the boat by keep it on its] trailer [is] not practical.

DRAIN TUBE INSPECTIONS
The [aft cockpit] drain [brass] tube [was] inspected in 2024 and in 2025. It appears to be in good shape and well sealed at both ends.


METEOROLOGICAL DATA
We get rain about three days out of seven. To cover the boat is not practical due to its frequent use. The rainfall averages four-inches-per-month average. A one-day thunderstorm can produce two inches of rain in 24-hours.

REMEDY IN USE NOW
THe drain plug is removed when rain is forecasted.

USE ON MOORINGS FOR 30 to 40 DAYS
There is going to be a period of 30 to 40 days where the boat will sit on a mooring unattended. A cover will be on, but that may not keep all water out of the boat. I am considering leaving the plug out, but 30 days seems like a very long time to have water sitting [in the cockpit].

Q4: is a period of 30-days with a 1985 SUPER SPORT 15 sitting on a mooring with the cockpit sump drain open a concern?

Q5: is a period of 30-days with a 1985 SUPER SPORT 15 sitting on a mooring with the cockpit sump drain open an. example of being over-cautious?

REASON FOR CONCERN ABOUT WATER IN COCKPIT
For reasons both of boat integrity and enjoyment, the water in the stern is a concern for --at the least--being wet feet.

[Multiple new topics that the author expects to raise soon in separate threads were mentioned. You are welcome to start new threads for each new topic--Moderator]

[goldstem]

[Your narrative description of your boat's static trim] seems about right. I had a lighter Mercury 50-HP engine on my 15 that sat this [same] way. I moved the [multiple] fuel tanks forward when [the boat was sitting unattended] so there was less water in it [perhaps means the stern].

Were I doing this long term I may have moved the battery [to be] under the steering console [from the transom area], but my boat was was only in the lake for a week--and also on Lake Winnipesauke.

I have also [energized from the boat battery] an automatic bilge pump for short times, but I don't use it for long stays as [the automatic pump would] likely drain the battery.


ASIDE: [New Topic]
Q6: how do you like the Tohatsu 60-HP engine?

I have been tempted [to buy] that 60-HP engine.

At our sailing club we have two [Tohatsu] 30-HP engines and love them.

[jimh]

Q1: is the boat waterline at rest (static trim) of my 1985 SUPER SPORT 15 (as described below in the long narrative) typical of this model based on your own experiences with this model?

Yes.

LONGER VERSION
I had a 1976 SPORT 15, which was the first year of that model, with a four cylinder in-line 44-cubic-inch Mercury two-stroke-power-cycle engine with electric start but no power trim. In these early model years, the hull laminate lay-up was a bit lighter than in layer models, and as a SPORT there was a bit less weight in the seating than in a 1985 SUPER SPORT 15, and the classic Mercury engine was probably rather light. However, and as best as I can recall, we never left the aft cockpit sump drain open to the sea when using the boat. And as best as I can recall we never had water in the sink-style engine splash well. If there were any water in the cockpit sump, we could drain it out while underway by removing the plug. Once the sump was dry, the plug went back in.

I do recall one particular situation with that boat. We had just gotten the boat, and we were taking it on a trip for the first time. And this was our first Boston Whaler boat.

The SPORT 15 was in the water at a shoreline dock at a small motel on the shore of a small lake, which provided the boat dock for its customers. The cockpit sump drain was plugged. On the first night staying there, it rained all night, and not just a drizzle. It poured for several hours. It was a big storm

The next morning I went to the dock to see how the boat survived the storm; it has been completely uncovered, and I expected there would be water in the cockpit. Yes, there was water in the cockpit, and quite a bit of water. It looked to me like the water level in the boat was actually higher than the water line, and from that I deduced that if I stepped aboard and removed the cockpit sump drain plug, the water would drain out. That was the theory I had, and I figured if it didn't work, I could always put the plug back in and remove the water with a bucket.

Making this situation a bit more interesting, there was another fellow's boat in the slip on the other side of the access dock, and his boat had similarly collected a lot of water. So much water, in fact that the boat was severely trimmed down by the stern, with the transom top almost under water. This was a small, maybe 16 or 17 foot runabout with a sterndrive, and the only thing keeping the boat from sinking lower was the skeg of the sterndrive was buried in the lake bottom.

I went aboard my SPORT 15, quickly pulled out the drain plug, and then I hopped back on the dock. As I had hoped, all the water in the boat drained out via the open cockpit sump drain, leaving just a small amount remaining in the stern that had overflowed the sump drain just a bit. I got back in the boat and put in the drain plug. Then I used a sponge to remove the rest of the water in the stern that had risen just above the sump and overflowed.

This was my first impression of the intelligent design incorporated in Boston Whaler boats. I was looking at my boat, now almost completely dry, and at the other guy's boat, a runabout with a stern drive, which was in a very bad situation, as the water looked like it had risen enough to get at the engine.

[jimh]

Here is a photograph of my SPORT 15 that shows the transom. Because there is a person sitting in the bow, the boat trim is affected. And there is a bit of list to starboard. But you can see how far out of the water the splash well drain is on port.


Fig. 1. View of SPORT 15 trim at transom.

[davidB01]

@Goldstem - Thank you for your comments. WRT your question on Tohatsu, sending you an email so we can talk about it without co-opting this this thread

@JimH - thank you for your edit streamlining my post. I am trying to get better, but still have a long way to go simplifying.

Also appreciate the comments, pictures, and the story. Yes, it does feel like the boat rides higher empty than the sea. I think this is why I get about 1.5 inches of water inside with the plug pulled, but the boat seems to only settle down about a half an inch further. So, your observation on the storm impact makes good sense to me.

With respect you your comments, and the picture, on where your boat sits, mine is definitely lower. Just for fun, I asked my wife to sit in the bow to more duplicate your pic and compare. (Ignore the Hummingbird sensor in the spashwell drain - bracket broke and I am waiting for a replacement) The big difference is I only have one full 6 gal tank and it looks like you might have an additional 12 gal tank in the stern. See below, but I would say that with someone in the bow (and we will NOT be comparing weights of spouses!), it halved the difference between your picture and my at-static observation. You commented that your boat may be lighter due to construction, that engine vs my new T60 (213 lbs), and the difference in the interior design, so that might make up the rest. Of course, mine just might be heavier, but, if so, if would feel like not much, or at least not enough to worry about.

Fig. 2. SUPER SPORT 15 showing trim at stern.

IMG_5534_1.jpg (112.01 KiB) Viewed 842 times

If anyone has other observations/thoughts on Q1, or wants to address the other questions, would appreciate your thoughts, especially with regard to Q4 or Q5.


Thank you.

[jimh]

Also influencing the static trim of the boat under discussion is the swim platform and boarding ladder seen in Figure 2 on the Port side: more added weight and right on the transom itself. Your engine probably weighs a bit more than my old 1976 Mercury 50-HP, and the hull itself is heavier, and there is more wood interior. So there is no surprise that the static trim might be slightly lower than I think it was as best as I can I remember for my 1976 SPORT 15.

As for whether or not to leave the aft cockpit sump drain open or plugged, I suggest you can leave it open when the boat is unattended and on your northern, freshwater, cold lake. The usual complaint about letting some water sit in the cockpit is there will be formation of algae and slime. However, if your northern, freshwater, cold lake is like mine (Lake Michigan), there should not be a very rapid accumulation or formation of algae and slime in any water sitting in the boat for a few days, as long as leaves or grasses don't blow into the sump to start something brewing.

Or equally as workable, you could leave the drain plugged, and if there is a hard rain you can remove the plug, drain all the rain water that accumulated, and put the plug back in place.

If the boat is at a dock, you should be able to cover it in some manner that won't be too difficult to put on or take off so that the whole interior of the boat--and all that nicely varnish wood--will be protected from the Sun and weather, and shedding rain will just be a bonus when it happens periodically.

[jimh]

ASIDE
In Figure 2 I see a pattern of what appears to be old screw fastener holes on the starboard side of the transom. My inference is the missing screws were previously used to hold a cable coming from a SONAR transducer that was attached on the starboard side.

[davidB01]

Hi Jim

Thank you for the confirmations and thoughts. I am feeling more reassured about the static trim. That said, wet feet, worries about water sitting in the [cockpit] for longer periods (though I agree with you that Northern Lake waters are less of a concern - we just crossed 70F as well), and difficulties of cleaning the boat when it will not easily drain will likely warrant a separate thread looking for advice in that regard.

For now, enjoying the first full season with the boat. It now goes out more than our big lake boat (27-footer) for runabout duties. Continue to work on plans for restoring over the next two seasons here (only can work on it May-Sept, which is when we want to be enjoying it!).

As for your last comment on the Aside - the screws are one of the remaining vestiges of a transom mounted speedometer and cable path back to the dash. These were removed when we repowered, but we did not have time to fully fix the gelcoat for this and other transom accessories. At the recommendation of the mechanic, rather than just plugging, we chose to embed fresh SS screws into the holes, betted with 4200 as a sealant, until we could more properly address them (one more thing on the list!). I do need to learn gel coat repair by next summer, so this might be where I start.