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Old 08-21-2006, 10:02 PM
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Default Seagull 19 CC single engine catamaran

I am looking hard at a 2001 Seagull single engine cat with a 130 four stroke. Current owner says it cavitates excessively above about 3700 rpm, but a dealer told him going to a four blade prop will cure this. Does anyone have any experience with this set up?

I think Pro Kat is basically making the same hull set up now, so experience with the Pro Kat might be applicable. The boat is about 19' 6", or thereabouts.

Any help on this will be greatly appreciated.



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Old 08-21-2006, 10:24 PM
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Default RE: Seagull 19 CC single engine catamaran

Try 4 blade prop and talk to the people at Prematrim in there forum. The prematrim helped out the kids Craig Cat. The guys at Permatrim where very helpful.
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Old 08-21-2006, 10:33 PM
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Default Re: Seagull 19 CC single engine catamaran

Thanks. The engine already has some kind of hydrofoil on the cavitation plate (I am going by pictures at this point), but it may not be big enough. The Permatrim looks a little bigger on their website.

Also, the current owner says the cavitation causes a lot of engine vibration--is that normal cavitation? I guess I think of just higher revs resulting from cavitation, but have no real experience with this kind of problem.

Anybody got a Seagull or ProKat with this problem?

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Old 08-21-2006, 10:42 PM
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Default Re: Seagull 19 CC single engine catamaran

Dropping it down a an inch or two will probably save the day.

The PK uses a 150.

The 4 blade prop will help you trim up and down better than a 3 blade, but I doubt if it will help cavitation caused by air getting to the prop mixed with water.

But if the motor computer reports a lot of hours, while it was cavitating, the engine will not be in good shape in terms of long life.

In any case I wouldn't consider it if the seller can't get it to run right in the first place.
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Old 08-21-2006, 10:49 PM
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Default Re: Seagull 19 CC single engine catamaran

Thanks. Dropping it lower was my first thought too. I guess that could be done with a jack plate?

Motor is low hours, and the boat apparently gets to a decent cruising speed at 3700 or less. I think the engine is probably ok.

10-4 on getting it right first.
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Old 08-21-2006, 11:24 PM
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Default Re: Seagull 19 CC single engine catamaran

Quote:
Cat-a-holic - 8/21/2006 10:49 PM

Thanks. Dropping it lower was my first thought too. I guess that could be done with a jack plate?

Motor is low hours, and the boat apparently gets to a decent cruising speed at 3700 or less. I think the engine is probably ok.

10-4 on getting it right first.
Motors have mounting holes. No need for jack plates to lower this IMO.
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Old 08-21-2006, 11:52 PM
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Default RE: Seagull 19 CC single engine catamaran

You may want to reconsider that purchase. The dealer I bought my boat from used to be a Seagull dealer. He told me that the boat line had serious quality issues. I was going to purchase a new 18' years back until another dealer told me that I would need to make sure any holes drilled in the deck would need to be well sealed because the wood that was used for the deck wasn't treated. Yet another dealer in Florida said that he owned a 19' and that it was a great boat... right up to the time it fell apart. I don't mean to be the bearer of bad news but these three instances by three different dealers in three different states changed my mind about buying a seagull.
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Old 08-22-2006, 06:56 AM
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Default Re: Seagull 19 CC single engine catamaran

Thanks for the advice. I have talked to former Segull dealer who told me that the quality/deck rot problems were limited to the models made in Mexico which had wood. This model is wood free and from what I can learn, is a good hull. I think this is true of the Nautico line as well in the 20' and over models.

Anyone out there worked thru the cavitation problem on the single engine Seagull or Pro Kat?
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Old 08-22-2006, 08:10 AM
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Default Re: Seagull 19 CC single engine catamaran

Okay, here we go. I have heard nothing but bad things on that hull prior to someone coming into the shop last week with motor problems. Brand new ProKat with a 150 Suzi. After fixing a half dozen or so 'F'ups by the maufacturer and the dealer(it's amazing what some dealers will let go out the door) I was ready to go for a sea trial. Hadn't driven a 150 yet so I was kind of anxious. Upon throttle up I really thought we had spun hub. No bite what so ever. Finally after powering throught the ventilation I managed to get some bite at about 5500 rpm's. Then you could back off the power some and still have some bite but slip was very evident. Then upon any throttle what so ever, it would just let loose and then you have to go throught power thru it, get up to over 5500 and then back it down. In a turn, forget about it. You might as well come off a plane. So needless to say I didn't get to see what that fine motor would do. Took that POS back to the dock and told the customer to go get his money back. The motor was mounted on the very last hole with a 4 blade prop. the only thign that will solve that is a jack plate mounted lower thant the current mounting holes so you can get the motor down 3, 4 maybe 5 inches. And even then, don''t know. The fact that the motor was already mounted that low tell me they know exactly what is happening with this hull.

My advice........for what it worth.......find another hull. Look at the 18 Caracal or 22 Seacat. And no don't consider the 20 Twin Vee. That boat has it's problems too.

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Old 08-22-2006, 08:40 AM
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Default Re: Seagull 19 CC single engine catamaran


Is this a chronic problem as the poster claims ? There have been tons
of posts and articles about these boats and this is the first time I've
seen uncontrollable cavitation to be a problem with them.
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Old 08-22-2006, 09:09 AM
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Default Re: Seagull 19 CC single engine catamaran

Problem is the weight of the motor not so much design. You put a 315lb motor on there instead of a 425lb+ motor and it will be night and day difference. I'd also reccomend the 18' Sea Cat its a great boat.
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Old 08-22-2006, 09:25 AM
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Default Re: Seagull 19 CC single engine catamaran

True, 18 Sea Cat is a good boat. I mistakingly left that one out. How you figure a lighter motor will help. Prop bite is prop bite. I lighter motor will have the ass-end up even more.
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Old 08-22-2006, 09:51 AM
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Default Re: Seagull 19 CC single engine catamaran

I cant explain it I know it doesnt seem to make sense but. I had some cavitation with the 18' Sea Cat not alot but i just thought it could be better. I put 2 or 3 different 4-blades on there and also added a permatrim plate and it made it better but still it would catch some air at times. So looking at the Leader Test results for that hull with a 70hp Suzuki it showed top speed of 33.2mph and Sea Cat showed it at 36.1 with a 115hp Suzuki so i got to thinking it has to be the weight of the motor since there wasnt much performance gained from an additional 45hp. So I traded my 115hp Suzuki 4-stroke for a 90hp Tohatsu TLDI it weighs over 100lbs less than the Suzuki. Now i have no cavitation at all and that is with a 3-blade prop. I hav'nt lost any speed, it still tops out around 35mph and my fuel consumption is as good as the Suzuki. I use to have a little water come in thru the scuppers at times now that is also gone. I think the weight was a big problem and i also think that 115hp was too much hp for the boat. I cant explain it from an egineering or physics side but i know it worked and I'm extremly happy with the boat.
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Old 08-22-2006, 09:53 AM
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Default Re: Seagull 19 CC single engine catamaran

Quote:
Bolton - 8/22/2006 9:25 AM

True, 18 Sea Cat is a good boat. I mistakingly left that one out. How you figure a lighter motor will help. Prop bite is prop bite. I lighter motor will have the ass-end up even more.
Agreed
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Old 08-22-2006, 10:02 AM
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Default Re: Seagull 19 CC single engine catamaran

Quote:
Bullshipper - 8/22/2006 9:53 AM

Quote:
Bolton - 8/22/2006 9:25 AM

True, 18 Sea Cat is a good boat. I mistakingly left that one out. How you figure a lighter motor will help. Prop bite is prop bite. I lighter motor will have the ass-end up even more.
Agreed

Just from experience i can say without a doubt this solved my problem not sure it would solve the posters problem. But I can say with confidence and experience the problem with mine was weight even the mechanic who test drove it afterwards couldnt believe the difference it made and he also agreed on the problem being the weight hanging off the back of the boat.
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Old 08-22-2006, 10:37 AM
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Default Re: Seagull 19 CC single engine catamaran

Just to be clear.

Cavitation is caused by water with entrained air going to the prop.

Slip is when the blade is leaving the water surface or is very close to the water surface where propulsion goes up and not back. Larger plates on the bottom of the OEM motr cavitation plate help this.

Water coming through cats tunnel WILL be air entrained do to the mixing with the strakes upstream.

This is why 90% of the cats are twins, placed behind the sponson that insures cleaner water than found in the tunnel.

The Seacat 18, Caracal 18, the Seagulls, PK 20, the Cat advantage, and a few others are the exception to the twin setup, but this has been a hurdle for all of them IMO.
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Old 08-22-2006, 11:07 AM
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Default Re: Seagull 19 CC single engine catamaran

I have a 20" Seagull with a 115 Suzuki. A 4 blade double cupped prop helped the ventilation problem. The weight thing is what fools me, as our boat rides better, less ventilation, better speed when our 28g transom livewell is full of water. When empty, the boat does not perform as well.
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Old 08-22-2006, 11:37 AM
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Default Re: Seagull 19 CC single engine catamaran

I agree single engine cats can have a few quirks, but what a great dry riding boat for its size. In that size range I think nothing compares. I cant imagine being in 18' of anything else that would touch the ride of the smaller cats.
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Old 08-22-2006, 04:48 PM
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Default Re: Seagull 19 CC single engine catamaran

Quote:
fishguts - 8/22/2006 11:07 AM

I have a 20" Seagull with a 115 Suzuki. A 4 blade double cupped prop helped the ventilation problem. The weight thing is what fools me, as our boat rides better, less ventilation, better speed when our 28g transom livewell is full of water. When empty, the boat does not perform as well.
More weight on the transom = a deeper prop = less slip= cleaner water= less cavitation too.
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Old 08-22-2006, 04:51 PM
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Default Re: Seagull 19 CC single engine catamaran

maybe on the Seagull its the ticket.....
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