21' Sea Cat max motor size question

[SparkieBoat]

My friend recently traded his 20 edgewater with a 200 yami that ran like a champ(50 MPH)for a 21 sea cat, he really loves the boat but it came with twin 70 rudes, max speed is about 30 mph. I have been looking at other 21 SCs and found one with twin 60s and a few with twin 90s, these all seem to be amazingly underpowered, is there any safety reason/other reason for these boats not being power so they can go faster that 30-40 mph or so?? I talked with a guy who had a 20 sea cat with twin 115 4-strokes and he said top speed was 40 MPH. I just cannot figure out for the life of me why these do not come with at least 115s, my choice would be a pair of 175s, just wondering what is up with this pattern of underpowered SCs. Any insight would be welcomed.
Thanks Sparkie

 

[SparkieBoat]

Re: 21' Sea Cat max motor size question

any ideas ????

 

[Gary H NC]

Re: 21' Sea Cat max motor size question

The boat should have a capacity sticker somewhere near the helm that states max hp for that model.
I bet he wishes he kept the 200 Yammie...

 

[SparkieBoat]

Re: 21' Sea Cat max motor size question

he also got some cash with the deal because the boat is under powered. I have talked to other Sea cat owners with the same model boat and they said the max HP rating is 180 HP. I talked with a guy who has twin 90s on his boat and it tops out at 35 mph. I can see no reason at all to at least go with 115s, I am still leaning toward 150/175s, at only 50 lbs more each it would be a easy trade off for the extra horses. boat floats plenty high enough out of the water, even when My friend and I sat on the 70s and we both weight 200 lbs, 115 4 strokes would not even weight too much.

 

[JB]

Re: 21' Sea Cat max motor size question

The boat should have a capacity sticker somewhere near the helm that states max hp for that model.
I bet he wishes he kept the 200 Yammie...

Yeah. I bet he wishes he kept the Edgewater, too. Folks who part with an Edgewater, Classic Boston Whaler, Everglades or other Bob Dougherty designed boat for fancy style in a much lower quality boat are almost always very dissatisfied.

 

[SparkieBoat]

Re: 21' Sea Cat max motor size question

the sea cat twin Vee hull provides more deck space for his kids (3) and wife and good storage area, also a noticeably smoother ride in choppy water, he also wanted a boat that had less draft so when fishing the flats in the sounds he would not bottom out. He is very satisfied with all but the power, wants to be able to run 45 MPH, I would think a pair of 150s should bust that wide open.

 

[Bama John]

Re: 21' Sea Cat max motor size question

I've got a '94 model and it is rated for 90hp each side. Mine has 60hp and it runs about 22mph give or take with two men and gear. Not fast but easy on gas.

If I was buying it again I would take the dealers recommendation and bought the 88spl that were available then. Please report back what your friend decides, I am curious how it works out.

 

[NYBo]

Re: 21' Sea Cat max motor size question

I would think a pair of 150s should bust that wide open.

If you're talking about the hull, I think that's a distinct possibility, either directly from the additional forces on the transom, or from speed a lot higher than the hull was designed for.

 

[Dave Abrahamson]

Re: 21' Sea Cat max motor size question

I can see no reason at all to at least go with 115s

This....

I have talked to other Sea cat owners with the same model boat and they said the max HP rating is 180 HP.

Is a pretty good reason,(at least for me), not to bolt 230hp to the transom(s)

 

[SparkieBoat]

Re: 21' Sea Cat max motor size question

I have seen lots and lots of boats over-powered with no problems. Probably half of the boats I have owned were over powered according to manufacturers rating. I have seen a few weak transoms crack (not on one of my boats though, cause I know how to seal the holes)and need to be replaced but they were starting to rot anyway. I always just figured that boat manufacturers routinely under rated their boats for legal reasons, I mean with all the law suit happy people CYA seems to be a common practice among all manufactures. the 90s weight the exact same as the 115s, only difference is the HP. My buddy sat on one of his 70s and I sat on the other and we are both 200 lbs, the boat did not sink much at all and the transoms showed absolutely no flex, they are very thick and sturdy, I would not hesitate to bolt a 250 on the thing as far as that goes. I was just wondering why I have not seen any of these particular models over powered, I have seen a couple of them with 115s, but not 150s. I guess I will just have to try it and see what happens, I have never ever even heard of a hull cracking because of exceeding the designed top speed by 10-15 MPH..now if I was going to put a pair of 300s on it and try to do 90, I could see a potential issue. Anyone else ever see a hull that was in good condition crack or suffer damage not cause by a collision???

 

[NYBo]

Re: 21' Sea Cat max motor size question

Mounting 300 HP on a hull rated for 180 is not just a little overpowering. Boats have a tendency for their handing to get real squirrelly when going significantly over design speed. Hit an unexpected wave at such speeds and your safety margin is gone.

If you run across a diligent LEO who knows his stuff, your voyage could be terminated.

 

[SparkieBoat]

Re: 21' Sea Cat max motor size question

Thanks for the input guys. It has been real helpful. Have a great day.