1995 Grady White Adventure 208 Top Speed Issue

[Toatts]

I just bought my first boat. I'm wondering a bit about speeds. I have a Yamaha f200 on it and at around 5500 rpm I only go about 28 mph. Is this normal? I saw and grady white's website that my boat (new) with a 200 will go about 42 mph.

That speed was recorded using navionics gps speed.

Prop dimensions are as follows

E3x14.8x19R
Solas
MYH

 

[Sea Rider]

Incorrect engine height and trim accounts for less water performance along wot rpm reduction when at full hammer down. What's the max wot rpm range for that motor, how loaded was the combo when achieved 5500 wot rpm at just 28 MPH ?

Happy Boating

 

[dingbat]

I just bought my first boat. I'm wondering a bit about speeds. I have a Yamaha f200 on it and at around 5500 rpm I only go about 28 mph. Is this normal? I saw and grady white's website that my boat (new) with a 200 will go about 42 mph.

That speed was recorded using navionics gps speed.

Prop dimensions are as follows

E3x14.8x19R
Solas
MYH

I ran 38+ mph with a 175 hp on my 208. My Grady 226 does 40 mph with a 200 on the back. Runs 30 mph @ 4200 rpm.

You obviously have something wrong.

The only thing that sticks out to me is the prop size. The Grady performance specifications are running a 14.25 x 17 prop, same size I ran on my 208.

Your running 3/4" larger diameter and 2" more inches of pitch and still (somewhat) making RPM.....Ideally should be propped closer to 6000. Makes me wonder if you don't have prop issues.

What condition is your prop? Either your prop is slipping horribly or your tachometer isn't accurate.
You have tabs?

 

[Toatts]

Sea Rider
dingbat

So I figured out the problem. I had a spun hub. When I took off the prop it looked like a bunch of twisted up rubber bands. It's a miracle that I didn't get stuck.

It was an aluminum prop. I went to get it repressed and the damn hub broke. I'm not all the upset because I got a stainless prop on order and its a 14.25 x 17. The engine guy said stainless is better because it has less flex and the size will be better for performance. Thanks for the help on this one guys!

 

[dingbat]

I got a stainless prop on order and its a 14.25 x 17. The engine guy said stainless is better because it has less flex and the size will be better for performance.

That boat deserves a stainless prop. have a Merc Enertia on my 226.

 

[Toatts]

I got a stainless 14.75x17 put on today. I didn't see much of a difference. What could be next? I checked my foam and every hatch i could and it all is dry, so i don't think i have a bunch of extra weight. Could it be something with the engine?

 

[dingbat]

I got a stainless 14.75x17 put on today. I didn't see much of a difference. What could be next? I checked my foam and every hatch i could and it all is dry, so i don't think i have a bunch of extra weight. Could it be something with the engine?

Make no sense at all.

Never heard of such a thing as a Grady with a foam issues.

17 pitch, 1.86 Ratio, 5500 RPM and 28 mph gives you 40% slip.

What prop are you running?
OEM lower unit?

Very well could be something with the motor if your WOT is only 5500 with a 17 pitch prop.

 

[dwco5051]

Have you tried trimming the motor up and/or down while running. Sounds a bit like the motor may be trimmed all the way down and you are plowing the water as opposed to be on plane at the sweet spot. That boat and motor should be able to do at least 35, maybe more depending on the load.

 

[Toatts]

Have you tried trimming the motor up and/or down while running. Sounds a bit like the motor may be trimmed all the way down and you are plowing the water as opposed to be on plane at the sweet spot. That boat and motor should be able to do at least 35, maybe more depending on the load.

I am an amateur boater, so that may be the issue. I'm going to take it out again this weekend and will update.

 

[Toatts]

So I watched this video on mounting engines. I THINK my engine is mounted too low. https://www.youtube.com/watch?v=N_EMx9WwTlY @ 3:50 he talks about the water pickups need to be in line with the bottom of the hull. My anti cavitation plate is level with the bottom of the boat. And then goes on to talk about if it is too low and water goes over the anti cavitation plate then you'll have a bow high ride. Well I have a bow high ride.

I'm hoping this is my problem because I'm getting the transom rebuilt which will result in the engine being remounted.

 

[WesNewell]

According to specs that boat weighs 2050# dry. Add 600# people and gear and 40 gal of fuel and it should hit 50 mph assuming the engine is mounted at the correct height and in good running condition. Recommended prop is 21P for f200 Yamaha.

 

[Toatts]

According to specs that boat weighs 2050# dry. Add 600# people and gear and 40 gal of fuel and it should hit 50 mph assuming the engine is mounted at the correct height and in good running condition. Recommended prop is 21P for f200 Yamaha.

https://www.gradywhite.com/models/walkaround-cabins/adventure-208/

 

[WesNewell]

Sorry, misread the weight. it's 2650# for the 1995. but not a lot of difference
http://boatspecs.iboats.com/Grady-White_Boats__208_Adventure__1995/bp/66b37568
[h=3]Your setup[/h]

• Boat type: Runabout - Cuddy
• Usage: Overall good performance/0 ft
• Engine Manufacturer:
  Yamaha
• Engine Type: Outboard
• Engine Year: 2005
• Number of Engines: One
• Engine Family: V6 4-Stroke
• Engine: F200 4-stroke
• Drive / Gear Case: Yamaha 200-250 hp 4S 2.0 Ratio

[h=3]Details[/h]

• Calculated Pitch: 20.68
• Calculated Weight with engine(s): 4,061.00 lbs
• Calculated Engine RPM: 5,500
• Calculated Boat Speed: 48.40 mph

 

[dingbat]

Sorry, misread the weight. it's 2650# for the 1995. but not a lot of difference
http://boatspecs.iboats.com/Grady-W...’t get the boat on plane with a 21 pitch prop

 

[dingbat]

I am an amateur boater, so that may be the issue. I'm going to take it out again this weekend and will update.

The hull is designed for rough water. It runs high in the water compared to most boats. Needs a prop with a lot of lift to get the bow up to running angle. Hydraulic trim tabs help tremendously, but you need the lift from the prop for best performance

The forward pointy of entry is right under the Captains feet. You can hear and feel the contact when the running angle of the hull is correct

If your applying negative trim to level out the boat you’ve found problem.

Start out with the motor perpendicular to the surface of the water. Get boat up on plane. Then slowing start trimming out. The rpm and speed will start to rise. Trim up until you max out the speed.

 

[Faztbullet]

https://www.youtube.com/watch?v=N_EMx9WwTlY
Very good video and explanation of mounting and why.

 

[Toatts]

https://www.youtube.com/watch?v=N_EMx9WwTlY
Very good video and explanation of mounting and why.

That's the video that has lead me down this investigative trail. Here's a pic of my engine at 4500 RPM 24-26KTS. Notice the anticavitation plate below the water line.

https://www.reddit.com/user/LemmeGetDatOC/comments/d8e5t7/engine_example/

 

[dingbat]

That's the video that has lead me down this investigative trail. Here's a pic of my engine at 4500 RPM 24-26KTS. Notice the anticavitation plate below the water line.

https://www.reddit.com/user/LemmeGet...ngine_example/

Wait a minute.....you need to get your unit of measure under control.
You say you run 24-26 kts (27 to 29 mpg) to at 4500 rpm but top out at 28 mph at 5500 rpm?

As comparison, I run 27 kts. (31 mph) at 4300 rpm. WOT 35 kts.(40.2 mph) at 5750 rpm

 

[Sea Rider]

Bad water performance will account as long there's a divorce between boat's transom and motor's lower leg heights which differs from manufacturer to manufacturer. There's usually a bad marriage associated to both situations..

What's the min-max wot rpm range for that motor ? Did motor gained some more wot rpm with new rop ? if so-so, need at least one less pitch to pull wot revs towards 6K which should be the max wot rpm range for that motor ?

Happy Boating

 

[Texasmark]

https://www.youtube.com/watch?v=N_EMx9WwTlY
Very good video and explanation of mounting and why.

I don't want everybody to run out and jack their engines up after seeing this so I have to reply:

I'm not a professional by any means, just talk about my experiences, but just from my limited boating experiences (18' max, 125 hp max, 55 MPH max, no progressive deep Vhulls to speak of), over the years, running the kind of boats most of us on here run, what you see in the video has it's applications.......wayyyyy more boat and power than most of us run.

For most of us (if I may be so bold), The AV plate even with the hull +/- 1" is more the norm, depending on a lot of things like the boat/engine configuration, type of water you run in, loads you carry, type of boating you like to do.....WOT all the time, Sunday afternoon cruise sort of thing. Trim is a super thing to have and learning how to use it effectively is a plus, surely.

I think Dingbat is the "Mentor" on this post as he is running the exact same rig on a daily basis in big water with big loads and making the performance.