Grady 305 Performance

[OSEAD]

I am looking for another owner of a 305 express I may be able to talk with. I am closing out my first season with the boat and overall we are very very pleased. However I would like to compare notes on the performance numbers you are seeing compared to mine.

I was seeing 27 knots/ 31 mph at 4500 rpm when i bought the boat. Now I am down to 22knots/25 mph at the same 4500 rpms. This is with the stock 15.25 x 19 saltwater series 3 blades. WOT i see 33Knots or about 37/38mph at 5600 if i trim up very high 5-7 bars on guage. WOT 5400 with normal trim 3 to 4 bars same speed. This is with full water, 120 gallons of fuel, diesel generator, 200lbs of gear 400lbs of people with my curtains up. All speed numbers are from my GPS

I recall the boat hitting 5900 when i sea trialed it and I double checked the survey and he got the same 5900/6000 wot rpm. I dont recall the speed at WOT. I do recall at the sea trial the boat had maybe 50-75 gallons of fuel, no gear, curtains up, 1000lbs of people weight. Boat Bottom very clean..

How do these numbers compare with other owners are seeing? I have studied the posts on the website but there is not much on the express. The Marlin owners all seem to do a a little better than me and the 305 express Grady performance reports..

What do you guys thinK? I am off Grady's reported top speed, and off on cruise numbers.. Do you think the bottom could be fouled enough even with a fresh bottom coat and that is slowing me down? how do these numbers compare to yours?

Thanks
Jim

 

[georgemjr]

I don't have specific 305 Express numbers, but a couple observations derived from both my 28 Sailfish and now 33 Express. First off, what type of power? You may be able to get more specific information from an owner with the exact same set up. What I have noticed is that fuel load does not make a very big difference and is not noticable on the 33, barely on the 28. So, I think the issue is something greater than the load difference. You might see a knot or .1mpg fuel burn difference but not much more than that. The bad news is you have to figure it out, the good news: when you do, you should see an appreciable increase in performance. You also were not talking about full loading as opposed to nearly empty, but somewhere in between. Good luck...

 

[OSEAD]

Thanks George I guess a few more details would help..

Its a 2007 Grady 305 Express
Twin 250hp Yamaha outboards
15.25 x 19 Yamaha Saltwater Series 2 props 3 blade
Holds 290 Gallons of Gas ( tested with between 50 -and 125 Gallons)
Full Water approx 35 Gallons
Diesel generator w 12 Gallons of Diesel Fuel
250 Lbs of gear

I have the Hard Top
Curtains up
Radar
22ft Lee Outriggers

Jim

 

[ocnslr]

Re: Grady 305 Performance ???

Bottom clean or has it been in the water for a while?

It doesn't take very much fouling (small barnacles) to drop performance as much as you have noted.

Based on personal experience...

Brian

 

[OSEAD]

Re: Grady 305 Performance ???

Brian

We put the boat in around May 15th. It had a fresh bottom coat then but has been in since. Thats about 6 mos.. I am thinking it could be the bottom as well. I only see slime but who know whats on the very bottom. Its so late in my season it wont be long before I find out when we haul it..

Ps we are in New Jersey

jim

 

[megabytes]

Re: Grady 305 Performance ???

By comparison, here are my numbers.

2004 300 w/F225
27-28 kts @ 4700 rpm
1.3 mpg (statute)
1.4 in inland waters (ICW)

 

[NOTHING ELSE MATTERS]

Re: Grady 305 Performance ???

Jim, i am in Long Island and we have the same season span. What i do in the middle of the season i haul the boat out, give it a nice touch with a pressure washer and put it back in. I too all i see when in the water is the slime by the water line, but that slime is under the whole boat giving her a lot of resistance. I don't really see any difference as far as speed and performance before and after, but i have 350's on mine. When i had the 306 and the 330 i was doing the same thing, but never noticed any drop on the performance,those boats both had F250's on them. Did you check for standing water/clogged bilge up front? 50-60 gallons of water in your boat up front it will make a big difference, your boat is bow heavy. I've seen in my marina a 305 that had standing water in the bow area and she was sitting very low up front in her slip.

 

[OSEAD]

Re: Grady 305 Performance ???

Thanks for the comments guys. I will check the Bow Today and see if thats the culprit..

Jim

 

[ocnslr]

Re: Grady 305 Performance ???

Understand only six months in the water.

I have seen a 2-3 knot drop in speed from a few dozen small barnacles on the trim tabs. And a larger drop from a few dozen more - all small - scattered around in a few areas.

It really doesn't take much to create very messy flow on the bottom, and make it much harder to move the boat through the water.

Brian

 

[OSEAD]

Re: Grady 305 Performance ???

I checked the forward Bilge and while there is a little water in there it was barely enough to be picked up by the Bilge pump. I dont think thats my issue. I took a closer look at the bottom and its pretty slimed over.. I am leaning towards that being the culptrit.

Any other ideas guys?

I will know if the bottom is Bad in the next few weeks when I pull her out. I would like to check for anything else so its not eating at me all winter.

Jim

 

[Hoghunter]

Re: Grady 305 Performance ???

I have a 305 Express that I bought new in 2007. I had a Marlin prior to that. My Marlin was always faster than my 305 and it really bothered me as they're both the same exact hull.

My boat like your's came with Yami 250's swinging the same 15.25 x 19 SS blades. The most I could ever get for WOT was maybe 5500 and more often than not it was 5300 to 5400 with top speed of 35 and at 4700 I was doing 28 to 30 mph. This is with bottom paint, full load of fuel and water, genset and fuel, tons of fishing gear, kicker motor, and enough spare parts and tools for probably three boats. I've also added bigger heavier batteries and a rather heavy inverter.

The one thing that always puzzled me is that the same year boat in a Marlin version with 250's had 15.25 x 17 blades. I had a spare set of the SS 15.25 x 17 blades which I had purchased for my previous Marlin. Last winter I pulled off the 19's and put on the 17's. Result: I got a totally different boat. It pops out of the hole now and I get 5900 to 6000 WOT. I can now cruise at 4700 to 4800 and will be doing 30 to 31 mph and I get better fuel economy to boot.

All I can say is I'm just ticked that I didn't put the 17" blades on three years ago.

 

[gerrys]

Re: Grady 305 Performance ???

Result: I got a totally different boat. It pops out of the hole now and I get 5900 to 6000 WOT. I can now cruise at 4700 to 4800 and will be doing 30 to 31 mph and I get better fuel economy to boot.

All I can say is I'm just ticked that I didn't put the 17" blades on three years ago.

What Hoghunter said!

Your numbers indicate you're over-propped. Slimy bottom makes it worse.

 

[OSEAD]

Re: Grady 305 Performance ???

Thanks for the posts and I agree thats it seems to be the 2 things you all have raised. Props and Bottom.. I have 4 blade props that I picked up from another member on the forum.. they are 15.25 x 16 power tech 4 blades. I will post my numbers later today on how that works out for me .

jim

 

[Grog]

Re: Grady 305 Performance ???

I'm out of Manasquan and there seems to be more slime/growth this year than previous years.

 

[BobP]

Re: Grady 305 Performance ???

Interesting.

Is there any growth on lower unit greaboxes ? Are they fully out of water during mooring?

And did you have equal conditions in sea conditions, wind, fuel loading, people, gear, water and waste tank, hot water heater, when you did the comparison? LW empty?

If not, load boat exactly as sea trail and wind and water, people, etc., and do it again.

I get hit with a mild gust at speed and there it is, watch the RPMs and gpm numbers and GPS speed take a hit and time to recover.

The boat is a substantial profile out of the water especially moving at speed, not so small as cars. Ever ride a bicylce into any head wind gust? Nearly brings you to a dead stop.

The faster the boat is moving the greater the boat takes a hit on any breeze if not steady (same for bikes!)

Even tail winds work to effect it.

 

[OSEAD]

Re: Grady 305 Performance ???

I put the four blades on ( 15.25 x 16) and here are the numbers I am getting now

This is with 140Gallons of fuel, canvas Up, 400lbs people, 20 Gallons water, Generator + 12 gallons fuel, Outriggers, 250lbs gear

Calm conditions in the river 7-10mph wind I averaged the Head wind and Tail wind results

6100 WOT 37/38mph .8 MPG full trim up 5-7 bars ( 6000 Rpms at 3-4 bars trim maybe 1 mph slower)
5500 35MPH 1.0MPG 4 bars trim
5000 30/31 MPH 1.1mpg 4 bars trim
4700 27/28 MPH 1.2mpg 4 bars trim
4500 25 mph 1.2mpg 3 bars trim
4000 20 mph ?? didnt record it 2 bars trim

How do these compare with yours HogHunter? I think I could add another inch of pitch and be dead on.. I am getting between 2 and 3/10ths of a MPG better with these props turning up to full rpm limit.. up from .9-1.0mpg and the bottom is still dirty!

I really want to get this boat dialed in for next year as you can tell

Jim

 

[OSEAD]

Re: Grady 305 Performance ???

Well i pulled the boat for the season and as suspected the bottom was covered with a pretty thick dark brown coat of slime. It came off pretty easily with the power washer. I dont recall ever having that much slime on the bottom. It was almost measurable :<>< . I am sure that it was affecting my speed the question is how much..

to recap i started with 19 inches of pitch 3 blades---dropped to 16inches pith 4 blades same diameter.

what do you guys think? maybe another 1in or 2 of pitch would be just right? I am thinking 17inches of pitch.

Jim

 

[Tashmoo]

Re: Grady 305 Performance ???

One other thing to consider.

I have seen the same type of drop in numbers on my 275. Under ideal condition in the beginning of the season the boat will hit 49 MPH, by the end of the season 45 MPH is a push. I think that the tide, current and wind conditions play a huge roll in top end. Bottom slim and the amount of junk that finds its way into the boat over a season factors in as well. That said, one thing that occurred to me is when I haul in the fall I put 91 octane gas in for the winter and stabilize it. During the season I put what is claimed to be 89 in. The reason I bring this up is that I use the same fuel dock all the time but last year I tanked up at a different fuel dock with what they claimed to be 89 octane and found that the boat was faster on that tank. I noticed no other difference.

It is certainly possible that the gas you use could have an impact of a few MPH. Fuel for thought.

 

[OSEAD]

Re: Grady 305 Performance ???

Thats a good point as well. Who knows maybe its old gas when I buy it.

Jim

 

[bayrat]

Re: Grady 305 Performance ???

""I was seeing 27 knots/ 31 mph at 4500 rpm when i bought the boat. Now I am down to 22knots/25 mph at the same 4500 rpms. This is with the stock 15.25 x 19 saltwater series 3 blades."

You've seen a 20% drop in speed since you've bought the boat. Not really understanding why you think all of a sudden its a prop/ pitch problem when you never touched the props. Logic says its something else, no? I agree with the other poster that performance deteriorates as you get to the end of the season. It happened every year with my last boat. Combination of bottom growth, barnacles , hull absorbing some water maybe, water in a bracket, if so equipped, can all make your boat heavier. I would be looking at all that before I started messing with props.If you store your boat out of the water Im pretty sure that it will perform better in the spring as it dries out...mine did. Maybe you are overpropped but that still doesn't explain the 20% drop in speed that you've had . Good luck in hunting it down.