repower for a 260 sundancer

G

gaiter

New Member
Feb 5, 2010
15
Ontario
Boat Info
1999 260 Sundancer
Engines
454 Mercruiser w/Bravo III Drive
I am thinking of repowering my 1999 260 sundancer. It currently has the 7.4LMPI in it and runs about 42mph at4300 or so. I was thinking of a 502 430 hp or somehting of the like. Has anyone done anything similar? If so how does the hull handle the extra hp?
 
gaiter said:
I am thinking of repowering my 1999 260 sundancer. It currently has the 7.4LMPI in it and runs about 42mph at4300 or so. I was thinking of a 502 430 hp or somehting of the like. Has anyone done anything similar? If so how does the hull handle the extra hp?
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It should like that motor a lot. Should get you close to 50mph too I would think.
 
Your current revs are low - you should be able to get those higher, and subsequently more speed.

Aside from that, repowering is a big investment and you likely will see very little return on investment. You'd see more speed, how much I don't know. I don't think you'd even see 10MPH, though - the hull just isn't designed for top end speed.

Is your current engine bad?

I don't know about engine mounts, so I can't comment on that. But, assuming for a minute that they match up, I don't think the boat/hull would suffer any adverse affects of bumping the HP

Of course you'll need an extra $1,600 for a new set of props.

Does anyone know what the HP limit is of a 1999 Bravo III?

Now, all that said, I must admit that I would certainly like to see someone do it... just not on my dime!:grin:
 
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I thiink you can put 500hp in front of the bravo III. I know my revs are a bit low, I am currntly turning a set of 24s and was thinking of trying the 22s before i lay up for the winter. leads me to another point though...my 24s are both 3 blade, looks like the new sets are a 4 blade in the front with a 3 blade aft. Any comments on this? Also, has anyone done any work on the 454mpi to boost it a little? I understand they are stone reliable stock....

And no, there is nothing wrong with my 454, it runs like a top with just over 400hrs on it.
 
lazy days - what are you running for props? What is your wot?
 
Just put a blower on your current 454! The question would be how much faster do you want to go? What is your goal? At that point there are some experts that can help you do it. I don't think the 502 is going to get more than 10 and I'm guessing that's optimistic. Seems like you need something like 50 hp for every 1 mph increase or something like that at those speeds. It's some crazy number! If you want to go faster it would probably be cheaper to sell your boat and buy a boat that is designed for and already has the equipment you need.
 
gaiter said:
lazy days - what are you running for props? What is your wot?
Click to expand...

I've got 22's. I'm not 100% positive on an exact top end RPM (I don't do it very much, at all... with this boat, that is:smt001), but I think I'm hovering around 4800.

I would assume that you have a different drive ratio, though. I'm not sure what my ratio is - I've repainted the drive and the old stickers were in bad shape so I just removed them. I'll have to check my ratio via my serial numbers, sometime.

Is your hull bottom clean?
 
Lazy Daze said:
I've got 22's. I'm not 100% positive on an exact top end RPM (I don't do it very much, at all... with this boat, that is:smt001), but I think I'm hovering around 4800.

I would assume that you have a different drive ratio, though. I'm not sure what my ratio is - I've repainted the drive and the old stickers were in bad shape so I just removed them. I'll have to check my ratio via my serial numbers, sometime.

Is your hull bottom clean?
Click to expand...
boat is bottom painted, but clean
 
I have been told the non-mag 454s cannot be modified without seriously shortening engine life. Also, assuming this engine has the peanut port heads, how much air can I force through there? Didn't really wnt to go thru hull either, and the exhaust is pretty restrictive.
 
The regular Bravo III can only handle 400hp. There are X and XR models of the Bravo III that can handle 450 and 525 hp. But you don't have that.

For new Merc motors you would be limited to the 496 MAG at 375hp or the 8.2 MAG at 380hp. About $15,000 installed.

The 4/3 blade Bravo III props give you a little better off the line performance but about the same top speed.

Your current props could be worn out. Have them rebuilt or buy new ones.
You can get good used or new prop sets for about $600 online. Try a set then sell them.

You will probably never get more than 50mph out of the boat safely.

In other words- Save your money and get another faster boat.
 
No Name Sea Ray said:
The regular Bravo III can only handle 400hp. There are X and XR models of the Bravo III that can handle 450 and 525 hp. But you don't have that.

For new Merc motors you would be limited to the 496 MAG at 375hp or the 8.2 MAG at 380hp. About $15,000 installed.

The 4/3 blade Bravo III props give you a little better off the line performance but about the same top speed.

Your current props could be worn out. Have them rebuilt or buy new ones.
You can get good used or new prop sets for about $600 online. Try a set then sell them.

You will probably never get more than 50mph out of the boat safely.

In other words- Save your money and get another faster boat.
Click to expand...
thanks for the info - I quickly read the merc site and assumed I was good to 525 without realizing that only applies to the XR. That complicates things a little...
 
No Name Sea Ray said:
The regular Bravo III can only handle 400hp.
Click to expand...

Do you recall if a 1999 B3 can handle 400HP? I could be wrong, but I thought there were some internal changes a few years ago to handle a little more HP?
 
400hp was what I was told for my 1997 Bravo III and that is what the current ones are. So I would assume Gaiter's 1999 is 400hp as well.
 
No Name Sea Ray said:
400hp was what I was told for my 1997 Bravo III and that is what the current ones are. So I would assume Gaiter's 1999 is 400hp as well.
Click to expand...

OK. Maybe the improvements were limited to NVH, then. Thanks:smt001
 
apparently GM doesn't make the 496 block anymore, thus the new 502 430hp
 
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