You are underpropped if you are getting 5200-5300 rpm. This assumes you have accurate tachometer. The WOT for my 6.2L engines for comparison is 4600-5000 rpm which is stamped on them. I get 34.4 mph at 4840 rpm with a clean bottom and 18x18 4 blade props. Increasing you prop pitch would most likely give better top end speed and get your rpm into the recommended range again assuming your rpm readings are accurate. My advice is validate your tachometer first and if accurate talk to a prop shop about getting your props scanned/tuned or replaces. I just replaced my props with Michigan Wheel DQX 4 blade 18x18 nibral props. With your bigger boat you might need something slightly different.

 

BOB, Please help me understand why SEARAY would put under propped props on one of there boats?? How does one know if he/she should should get biggger/more blades? props, if one is going to pay over 250 K on a boat he should have the right props, what am i missing???:huh:

 

True - underpowered and not enough bite. Make sure your RPMs are accurate, then take your data to a professional prop shop to have more bite put in the blades and perhaps some cupping. They should know what to do. Also, have the Sea Ray stats ready - the way they recommend the props to be. Also, know what your max WOT RPMs should be. Good luck. I'm really surprised you're getting 36 mph - that's not bad in this boat, if it's the new 340 (changed in 2003 1/2).

 

.......I'm really surprised you're getting 36 mph - that's not bad in this boat.....

+1. That's a great WOT speed number with 6.2s --- in both the new AND old 340. I bet some 320 owners would like to see 36 mph. I agree with the others that prop work should take care of your problem and give you better planing & cruising performance, and get those RPMs down. Hopefully, you can keep that 36 mph top speed number.

 

Bob just beat me to it.

 

This is a f*cking joke... right?

Give me a break...

"Yeah... You should b!tch some more about that poor performance.. you are cool."

Did the "boating crowd" leave CSR? Are we just left with a bunch of 19 year old idiots now?

 

This is a f*cking joke... right?

Give me a break...

"Yeah... You should b!tch some more about that poor performance.. you are cool."

Did the "boating crowd" leave CSR? Are we just left with a bunch of 19 year old idiots now?

36MPH is about my max with a lighter boat. The 6.2's are a bit more powerful but not that much. You should be right where you should be but I would verify your RPM's.

 

You could tweak the props a little if your truly hitting 5,300rpm but other than that it sounds like your boat is right on the money.

 

Is this your first boat? or your first boat with inboards? Did you do any research before buying it? If you want a go-fast cruiser you should have purchased a Formula SS. http://www.boattest.com/boats/test_results_PrintP-e-oem.aspx?id=1870

If that isnt fast enough you should consider a Skater. http://www.skaterpowerboats.com/

Your numbers line up pretty close with Boat Test reports and they tested using big blocks. There doesn't appear to be anything wrong with your boat, the problem is with your expectations.

http://www.boattest.com/boats/boat_video.aspx?id=75#Test-Result

 

Oh boy, 4 Suns is gonna get a whippin on this one......

 

Rip out the 6.2s and drop in some 8.1s. Maybe a nitro tank too.

 

Funny thing... I have not seen how fast my boat goes at WOT. I have gone 31 MPH at 4000 RPM, but I have not yet pushed it to WOT... I will have to try that this week end... I have new SS Hi-TEK headers on my 340, and only 1/4 tank of gas... I bet I can get 38 MPH... Alex, maybe we can have a race??? Looser buys... Its good to have a mind of 19 year old:thumbsup:, I only wish my body was only 19...:smt043

 

Funny thing... I have not seen how fast my boat goes at WOT. I have gone 31 MPH at 4000 RPM, but I have not yet pushed it to WOT... I will have to try that this week end... I have new SS Hi-TEK headers on my 340, and only 1/4 tank of gas... I bet I can get 38 MPH... Alex, maybe we can have a race??? Looser buys... Its good to have a mind of 19 year old:thumbsup:, I only wish my body was only 19...:smt043

I am assuming you have 380HP from those old big blocks so you just might be able to do it. The 454 in my previous boat was only 310 HP. A fellow at my marina with a 1998 Maxum 3700 bought his boat specifically to get your engines since he was told by someone in the know that for that year they were better than the 8.1s since they had dual overhead cams I believe. I hope yours are not as noisy as his at start up. It sounds like we are at a NASCAR track.:grin:

 

I am assuming you have 380HP from those old big blocks

Rod has the previous generation 340, which is essentially built on the hull of the 330 that it replaced in SR's lineup. As such, his boat is lighter, narrower and shorter than the 340 incarnation that the original poster has. I'll bet Rod does get up to and over 36mph with a light load and he'd likely beat Alex in a race. About all I could do in that race would be shoot the starting gun!

 

...About all I could do in that race would be shoot the starting gun!

Knowing your limitations I guess must mean you're not a 19-year-old!:smt043

 

You have purchased the wrong boat for your needs. Sell the boat and by something else.

http://formulaboatsforum.com/

http://www.donzi.net/forums/index.php

http://www.superboatonline.com/

 

I don't think the 6.2L is considered a big block. I've heard it has more top end than the 5.7L, and about 320 hp. The big blocks, 7.4L and 8.1L, have more torque at the low end, and are 310hp and 375hp, respectively.

 

I don't think the 6.2L is considered a big block.

The 6.2 is a stroked small block (longer stroke). They are rated at 320 hp.

 

I guess must mean you're not a 19-year-old!

Nah, it just means I know enough to NOT enter a 3 legged horse in the Preakness!

 

The normally aspirated 5.7L makes 250HP, the Mag Horizon MPI makes 300HP and the 6.2L makes 320HP. They are all basically the same 350cubic inch GM engine.

 

I know what you mean. On Saturday I was on a friend's boat. At 3500 RPM we were getting just over 60 MPH. On the way back, he let her run to 4200 RPM and we were seeing speeds in the low 70s and the engines are rated to turn another 1500 RPM.

Then on Sunday we were on my boat. At 3500 RPM all I got was a lousy 26 knots.

But I know what I need to do. I just need to narrow the hull down to 8', increase the deadrise to 25 degrees, add steps, pad, notch the transom and drop 3,000 lbs. Then need to swap the engines for 800 hp Marine Innovation 677 cid big blocks, add Gil stainless dry headers and back them up with Arneson Surface Drives.

And a guy in the know said that it's a simple and cheap upgrade that I can do at home in my own garage.

 

But I know what I need to do. I just need to narrow the hull down to 8', increase the deadrise to 25 degrees, add steps, pad, notch the transom and drop 3,000 lbs. Then need to swap the engines for 800 hp Marine Innovation 677 cid big blocks, add Gil stainless dry headers and back them up with Arneson Surface Drives.

And a guy in the know said that it's a simple and cheap upgrade that I can do at home in my own garage.

All you need to do is buy this boat. A good freind of mines latest venture. Only 3000HP and does 185mph.

http://www.youtube.com/watch?v=Wsc_qmnmKLw:thumbsup:

 

Thank you Bob.....very good explanation....:thumbsup:

 

Seriously, you want to get more MPH out of that tub? You must have more money than common sense.

 

This thread started out as a complaint... the subject of "Underpowered and Frustrated" is a statement and not a question. Additionally this thread started after this thread:

http://clubsearay.com/forum/showthread.php?t=36292

Some guy complaining about performance of a newer 40' Sundancer because it won't go 40mph and then some dope head coming in and saying "Just run it WOT all the time."...

and then this thread pops up with a guy complaining because his Sundancer will only go 36 mph...

One has to wonder what kind of research or knowledge people obtain before buying a boat... Surely the operational envelope of a $100K+++ item is a basic thing someone would know before taking the boat out... or writing the check... maybe not...

 

Nope............The sync gauge is driven by the tach signal and has nothing to do with the prop rpms.

John's comment is relative only to some but not all ZF transmission where the design is such that the reverse gear has a slightly different final drive ratio than forward. The difference is minescule....like 2.48:1 one way and vs 2.476:1 the other and is easily handled by minor differences in prop pitch or cup between the port and stbd sides. You will never know there is a difference in the way the boat runs or handles and most people only find there is a difference when they have their props trued and balanced.

 

Thanks Frank..

 

thanks Bob for actually understanding the question....the problem is not the top end speed but rather the poor responsiveness when I'm walking it around the marina. I'm looking into some bigger wheels right to gain some control. I've checked the tachs and they are correct. How are the 18x18 working out when you're moving it around.....ie. When you split the shifter sticks is there a long lag before you pivot?

 

thanks Bob for actually understanding the question....the problem is not the top end speed but rather the poor responsiveness when I'm walking it around the marina. I'm looking into some bigger wheels right to gain some control. I've checked the tachs and they are correct. How are the 18x18 working out when you're moving it around.....ie. When you split the shifter sticks is there a long lag before you pivot?

This is the 2003 prop spec from the Sea Ray site for your boat and engine combination:

2003
340SDA
TVD-MX 6.2 MPI (T-320 PHP) MCM V-DR.INBOARD
2.00:1
PROP, 17"X 19"X 3.55" "C" RH
1752161
PROP, 17"X 19"X 3.55" "C" LH
1752160

WOT 5200

According to this, your boat gets more top end rpm than mine even though we have the same engine and horsepower. I found the 4 blade props gave me a little more low end thrust in both reverse and forward for docking. They also gave me slightly better gas mileage and run smoother than the factory 3 blades. None of these improvements were large but rather incremental. I would suggest you start with a prop shop that has the prop scanning system like Airmarine here in Chicago. If your props are factory, they are 1" less in diameter than mine so I would check first if your prop tunnels can handle a larger diameter prop before considering that type of change. A good prop shop can then make a recommendation on what size and pitch props would be the best fit. Going with new props like mine will run you between $1,800 and $2,200 so make sure that a simple prop tuning which might run around $500 + could give you the improvements you are looking for. You are currently at or slightly above the WOT range but I would check what is stamped on your engines to validate what Sea Ray has on their site or is in your Mercruiser manual.

 

some quality advise Bob thanks.....I'm headed for the prop shop today......

 

I owned a 320 and you are not going to get what you desire. The only way to make a 320 (or most gas engines in this size boat) is to use a little bit of throttle when trying to spin the boat. By just placing one in forward the other reverse, it moves but it takes time. In the wind or current, forget it, you need throttle.

 

BIG DITTO:thumbsup::thumbsup:

 

This thread is a prime example of how one gets bad advice on the Internet (and people believe it)...

Time to bring back the red balls.

 

I've still got some greenies for sale. buyer backed out ^^^^^^^^^

 

You may want to try and sell your green balls to the guys telling this poster that, even though his boat is running at the published spec, he should go to the local prop shop because they'll know more than Sea Ray or Mercruiser... And what's wrong with propping the boat for more "bite" even though it won't be able to get to WOT spec?! That whole discussion on "engine overloading" is crap... they guys at the dock "in the know" said so...

This thread is about a guy who doesn't understand the performance envelope of his boat and has expectations that it's a Formula or something and then a few try to convince him that he should head off to the prop shop and spend $$ because... well... just because...

My "advise" is to

1. Call Sea Ray and get the performance specs (speed, RPM, etc) for your boat and engines.

2. Read the manual

3. Go to Boat Test and get the performance specs for your boat and engines.

4. Reset your expectations.

5. Take a boating class and buy some reference material

6. Don't listen to people who don't know which side of the day marker you should be on (The "It ain't boating unless you're bumping bottom" club)