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Help with 18' Cat Craft catamaran

Old 05-05-2021, 07:32 PM
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I’ve had three Caracal’s. All seemed to be lower than yours.

Etec 150 HO

Suzuki 140
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Old 05-05-2021, 10:26 PM
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if the hull is waterlogged it will drip water slowly when on the trailer, tilted up at the bow.

After leaving it for a day or two with the drain plugs out, you can then place a couple of pieces of paper under them. If it still continues to drip, it will stain the paper.
Old 05-06-2021, 04:00 PM
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Doing 33/34 mph in that hull sounds about right with a t-top and a 115. I doubt you have any bad water-logging going on. So, that’s good news.
Old 05-06-2021, 10:26 PM
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This Seagull is around 26 years old, has some wood , most likely some foam, and a lot of old drill holes.

So tilting her up to see if she will lose some weight while on her trailer is a good idea imo.

But until the bow comes down, the ttop is at an angle that pulls a lot of air slowing him down. The hull should plane at 2000 rpms, not 5000.
Old 05-08-2021, 04:14 PM
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I took some pictures with the boat sitting at the same level it does in the water. It seems like it has quite a bit of tuck already, so I may start by dropping it a hole first. Do you think this is enough? Another friend suggested that I should start with the motor trimmed up a bit so I don't lift the stern up so much and out of the clean water.




Old 05-08-2021, 05:24 PM
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The ideal is to move weight forward so that the hull floor is sloped up 2 degree when at rest or when running with neutral engine trim.

If you cannot balance the hull that way with weight, you need need to use power and create more angle with the wedges so that the propeller will its thrust more towards the bottom of the ocean. Seagull didn't do that, so you have to fix their lack of effort.

Pushing up at the stern will lower the bow.

The trim range on most OB motors is about -5 to 15 degrees off of vertical when sitting on a transom that is usually angled about 11 degrees. The wedges will change your range to a -11 to 10 degrees off of vertical. Suzuki doesn't spec the tuck in angle, but your photo with the vertical level tells the story.

Lowering the engine will get cleaner water to the prop, but will not increase the prop thrust angle.



Old 05-08-2021, 05:39 PM
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Here's a shot with the engine mounted with the lowest hole. I'm going to give this a try and will see if I still need to wedges.


Last edited by Shooterschmidty; 05-08-2021 at 06:01 PM.
Old 05-08-2021, 06:39 PM
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Originally Posted by Bullshipper View Post

Lowering the engine will get cleaner water to the prop, but will not increase the prop thrust angle.
Copy that. I figured the cleaner water may increase the effectiveness of my prop and permatrim and give me more pitch control. I'll test this variable and then slap on the wedges easily if needed. I'm becoming better at removing this engine than I'd really like at this point!
Old 05-09-2021, 06:17 PM
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I tested to l the boat today with the engine on the lowest bolt hole. Almost all of my ventilation at cruise is gone and it does seem to get up in plane a bit faster with less ventilation. Actually trimming up a bit on takeoff seemed to help, which was surprising to me. I still think that my bow control is marginal, and I find myself cruising trimmed all the way down if there's any chop, so I might still end up installing the wedges.
Old 05-09-2021, 09:37 PM
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All right, less ventilation, good.

But before you buy the wedges, I will give you something to think about.

Is the hull level sitting at rest? -
A picture taken from from the side with you and your passenger in the hull will show you. If she how stern heavy she is.
Trimming up the motor prior to take off will direct the prop thrust more level to the water surface and explain why she planed faster than when trimmed down.
If the hull is unlevel in the water you need to make her climb up and over a steeper hump using more rpms.
So shifting and weight forward will help with that, especially at rest when a hull really shows her bad manners on the drift in rough seas. Moving coolers, batteries, anchors, downriggers, cast nets, and or you and your buddy stepping farther forward will help her get on plane, if this is possible with your layout..

Is the deck and ttop level with the keel? Level with the water when on plane?
Another picture of you from the side while cruising will tell you if the top was installed to run level to the running surface of the ocean to reduce air drag and also determine if the top is holding the bow up like a Marty Poppins umbrella when cruising.
Another test would be to unlash the shade material and bunch it up or remove it to see if the top is slowing you down by more than 5 mph, and also see if a change in ttop angle will let you get the bow down more at a slower speed and rpms.

Can you still get 6000 rpms trimmed all the way down?

I am not changing my mind about the wedges, but correcting the top and hull inclination angle when sitting and running is the first thing to check out and correct if that was also set up by someone less competent than you.

Last edited by Bullshipper; 05-09-2021 at 09:54 PM.
Old 05-16-2021, 09:28 AM
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Originally Posted by Bullshipper View Post
All right, less ventilation, good.

But before you buy the wedges, I will give you something to think about.

Is the hull level sitting at rest? -
A picture taken from from the side with you and your passenger in the hull will show you. If she how stern heavy she is.
Trimming up the motor prior to take off will direct the prop thrust more level to the water surface and explain why she planed faster than when trimmed down.
If the hull is unlevel in the water you need to make her climb up and over a steeper hump using more rpms.
So shifting and weight forward will help with that, especially at rest when a hull really shows her bad manners on the drift in rough seas. Moving coolers, batteries, anchors, downriggers, cast nets, and or you and your buddy stepping farther forward will help her get on plane, if this is possible with your layout..

Is the deck and ttop level with the keel? Level with the water when on plane?
Another picture of you from the side while cruising will tell you if the top was installed to run level to the running surface of the ocean to reduce air drag and also determine if the top is holding the bow up like a Marty Poppins umbrella when cruising.
Another test would be to unlash the shade material and bunch it up or remove it to see if the top is slowing you down by more than 5 mph, and also see if a change in ttop angle will let you get the bow down more at a slower speed and rpms.

Can you still get 6000 rpms trimmed all the way down?

I am not changing my mind about the wedges, but correcting the top and hull inclination angle when sitting and running is the first thing to check out and correct if that was also set up by someone less competent than you.
I had the boat out this weekend striper fishing and took a few measurements. The T-top definitely isn't parallel to the water when I'm on plane. Over the length of the top, I'd probably have to bring the back up by 4-6" to make it level, so I probably am getting some parachute effect. I also have an electronics box and t-bag (see picture) that would also cause drag. I'd like to keep the T-top, box, and bag but I'll try removing the fabric next time I'm out. I could get the T-top cut and rewelded to make it parallel if necessary and I could probably fit the radio and stereo in the center console if I moved a few things. Alternatively, I could properly install some trim tabs, although this hull has limited real estate for those.


"Accessories" installed by previous owner.

It sits pretty level front to back and side to side at rest.
Old 05-16-2021, 10:24 AM
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Originally Posted by Bullshipper View Post

Can you still get 6000 rpms trimmed all the way down?
Yep, I can still hit right around 6000. Trimmed up to just the point where it starts porpoising one of my props, the one with less cupping, will actually overrev if I'm not careful.
Old 05-16-2021, 06:20 PM
  #53  
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I don't see a thing wrong with the top sitting there.

The hull should rise at the bow around 2% and the height of the top front to back are usually weld up to be the same height measuring up from the deck.

But on plane or on your trailer, I would consider anything over 2-3% inclination a problem and 3% x 72" = 2" difference in height measuring from the water or a 6' level, so if you think it needs 4-6" to correct it than that means the hull is probably tilted about 4-6 degrees when it should be around 2, like we have been talking about.

Getting the bow to drop with more forward weight should reduce the attack angle, the wind and water drag, so can test ithat by watching your gps and ask 2 buddies to move father forward to see the speed and or rpms go faster as their weight, while you slightly lower the trim angle on the motor, moving you faster on the gps without moving the throttles.

If it does, I would get the wedges, but if it doesn't improve your speed at least 5-10%, I would call it a day and just fish her as is, as she is running better now.

The question I had about the trim was not when trimming up, but when trimming all the way down, because a hull that is set up right, will lose speed and rpms when you can bury the bow with the motor, letting you trim down even when your guys all want to be in the back of the hull.

So if you can get 6000 trimmed all the way down at full throttle, it needs wedges and maybe even a faster prop with more pitch and used props are 50% cheaper here on the hull truth or on ebay.

Last edited by Bullshipper; 05-16-2021 at 06:32 PM.
Old 06-08-2021, 07:35 PM
  #54  
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I have an update. I installed five degree wedges and gave them a try on Sunday. I'm happy to report that they greatly improved my ability to bring the bow down and get the boat up on plane. I found that it was best to start with the engine trimmed up a bit too get the thrust pointing straight ahead and then once I had a bit of speed I actually trimmed down to "pop" the stern up and bring the bow down. Once on plane I trimmed up until the boat started to porpoise and then dropped it a bit from there. It seems to work pretty well, although I am curious to see how efficiently it runs.

I still want to try experimenting with the top fabric removed, but for now I'm pretty happy with how the boat performs.

Thanks again to everyone that helped. I'll keep updating this thread if I make any more improvements so there will be a record for the next guy or gal.
Old 06-08-2021, 08:17 PM
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WTG on coming up with your planning procedure.

Feathering won't take much practice, but it'll really pay off in a rough head sea.

Now that you have some better tools, you clearly get it.


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