13 GLS and Large Stern Wave

Optimizing the performance of Boston Whaler boats
sjp2
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13 GLS and Large Stern Wave

Postby sjp2 » Fri Nov 16, 2018 2:23 pm

In a small creek the other day [in a Boston Whaler 13 GLS boat] with four adults aboard and powered by a Yamaha 40-HP two-stroke-power-cycle engine with fuel and battery, and well before I was to pass another boat or kayak, I had to slow down to a crawl due to the size of the stern wave the boat was creating. The waves looked almost big enough to surf on. I was also concerned about the damage the wash was doing to the shoreline.

How can creation of large stern waves be lessened?

jimh
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Re: 13 GLS and Large Stern Wave

Postby jimh » Fri Nov 16, 2018 2:39 pm

To reduce the size of the boat wake, reduce draft at the transom, Also, as you noted, reduce speed.

Modern water-sport boats often have water ballast tanks in their stern to intentionally increase draft at the transom in order to create large wakes for the purpose of surfing on them.

sjp2
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Re: 13 GLS and Large Stern Wave

Postby sjp2 » Fri Nov 16, 2018 4:20 pm

I might move the fibreglass seat console setup about 6-inches forward--it is pretty heavy.

Battery is under console but the fuel was at the [stern].

I know that the 40-HP engine is allowable, but I often think an engine 40 to 50-lbs lighter hanging off the stern might better suit the boat. For example, a 30-HP.

I will look up some performance.

I will post later.

flymo
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Re: 13 GLS and Large Stern Wave

Postby flymo » Sat Nov 17, 2018 8:29 am

You had a big load in that little boat. To reduce the size of the wake you'd need to reduce the load, slow down, or speed up to get fully up on plane. Any time you're plowing along, trying to go faster but not really planing, you're making a huge wake - not to mention straining your motor.

Jefecinco
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Re: 13 GLS and Large Stern Wave

Postby Jefecinco » Sun Nov 18, 2018 10:10 am

We live on the ICW and see a lot of wakes. We see the least damaging wakes from boats that are either fully on plane or running at idle speed. The worst wakes come from large sport yachts plowing along at their minimal planing speed. I find it difficult to understand operators who spend a lot of time plowing as that has to be about the least fuel efficient operating speed for a boat of any size.
Butch

sjp2
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Re: 13 GLS and Large Stern Wave

Postby sjp2 » Sun Nov 18, 2018 2:29 pm

There is a big difference [in the wake height] between idling speed and planing speed. Factors like wind and tide [affect wake height].

Boston Whaler added a bit of weight to the GLS with that console, the seat setup is glass over wood compared to the simple wood console and seats, plus the foward control. An E-TEC 30's weight is not going to help much, either.

jimh
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Re: 13 GLS and Large Stern Wave

Postby jimh » Sun Nov 18, 2018 11:47 pm

If the four people in the boat each weigh 200-lbs, then a slight weight increase from fiberglass molded seats or a modern engine is insignificant in comparison.

Jefecinco
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Re: 13 GLS and Large Stern Wave

Postby Jefecinco » Mon Nov 19, 2018 10:17 am

I don't understand how wind and tide affect wake height.
Butch

dtmackey
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Re: 13 GLS and Large Stern Wave

Postby dtmackey » Mon Nov 19, 2018 10:23 pm

Jefecinco wrote:We live on the ICW and see a lot of wakes. We see the least damaging wakes from boats that are either fully on plane or running at idle speed. The worst wakes come from large sport yachts plowing along at their minimal planing speed. I find it difficult to understand operators who spend a lot of time plowing as that has to be about the least fuel efficient operating speed for a boat of any size.


[Strongly agrees.]

You can play with different engines, but boat loading, hull design and speed have a bigger influence on wake. I struggle with this in various places that have set speed limits and at the required speed I leave a bigger wake, but if I exceed the required speed, I leave a lesser wake.

This problem is not boat specific and I've noticed this in the following boats:

8' Avon
9.5' AB RIB
13' Whaler
15' Whaler
17' Whaler
20' Mako
21' Mako

Various boats over 21', including Coast Guard boats that have an idle speed of 8 kts.


D-

Don SSDD
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Re: 13 GLS and Large Stern Wave

Postby Don SSDD » Tue Nov 20, 2018 8:53 am

Places have speed limits to reduce wake and they only enforce the speed limit. What is really needed is a wake height limit but most landlubbers (and some boaters) equate high speed with a big wake but that is not always true, going fast can produce a smaller wake than going slow. Speed is easier to enforce than wake size but most times it is both speed and wake size that needs to be limited.
1986 Outrage 18 with 2001 Honda 130 HP
Former Owner 1991 Guardian 19 with 1994 Evinrude V4 140HP
Former owner 1987 Montauk with 1998 Mercury 90HP
Nova Scotia

Jefecinco
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Re: 13 GLS and Large Stern Wave

Postby Jefecinco » Tue Nov 20, 2018 10:56 am

I have seen areas with a speed limit of "Idle Speed Only" posted. Off hand I don't remember where. The more common signage limiting speed is "No Wake Zone". It is often enforced rather unevenly. Large boats are left alone if their wakes are not very high. Perhaps it's because they need a little more speed to maintain steering control in narrow channels. The little jet skis seem to be ticketed more often than others and the wakes they make, even at speed, are negligible compared to the large head boats. The Perdido Pass waters in Orange Beach are a good example of this.
Butch

Yellowjacket
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Re: 13 GLS and Large Stern Wave

Postby Yellowjacket » Wed Nov 21, 2018 5:53 pm

Get some weight forward. The more weight you move forward, the lower the wake will be. If it's a 13' boat, jut putting one person on the bow seat will significantly reduce the wake. With too much weight aft, you are pushing a lot of water and the wake will be much bigger.

sjp2
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Re: 13 GLS and Large Stern Wave

Postby sjp2 » Fri Nov 23, 2018 5:07 am

spot on Yellowjacket , that might have been the simple solution although i didn't think about it at the time, guess we all wanted to stay out of the sun under the canopy ,but the weight distribution towards the bow makes the most sense .