Grady 205 with 3.3 f250 cant hit 50mph

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TinkerinMatt

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I bought a 2005 tournament 205 with an f150 and no bottom paint and it only did 39.5 with the wind. Bought a 2005 f250 and a used “not perfect” saltwater series II prop 15 1/4 x 19p and it would do 48 one way 46 the other (current and wind in the intracoastal), but it was hitting 6100rpm so I thought either its the damage on the prop or too low of pitch. Bought a clean same pitch and size prop and tested it today and no change to top speed and still about 6000rpm.

Before the cuddy version of the 20’ hull was discontinued I saw a performance report, albeit with the 4.2 250, of it doing I think 55. I want to go 50+

What prop and what motor height should I be at? This is driving me nuts that I can’t do 50+. I’m at the second hole from the top, cav plate is level, what is wrong?
 
Not exactly an apples to apples comparison or anything, but I've had my 2004 Grady White 228 Seafarer with a hardtop, bottom paint and 04 Yamaha F225 on it up to 44-45 mph several times before. As stated, boat has bottom paint on it, around 1k hours on the motor, unknown on the pitch/size of the prop, but with 1/2-2/3 of a full fuel tank, light amount of gear, etc... I've hit 44-45 mph several times in my boat. Definitely helps if you have the wind/current at your back and you trim the motor up some. But I don't imagine there's any reason why you shouldn't be able to get at 50+ mph, as you've got a smaller, lighter boat than I have, and you have more horsepower than I do. If there aren't any mechanical issues with the motor itself, I'd start by giving Ken @ PropGods a call with your prop specs and see what he has to say on the matter. As mentioned above, weather/wind/conditions can definitely effect top speeds, as can adjusting trim tabs, motor height/trim, etc. Lastly, a brand new Grady White 215 Freedom with a single Yamaha F250 on it can top out at almost 49 mph. Again, not exactly an apples to apples comparison but with it being a bigger, heavier boat than yours... I would think you should be getting at least those numbers, if not better. They used a prop with the specs of "15 1/2 x 17 SWS II SDS" for the test, for what it's worth.
 
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what do you mean by the anti-ventilation plate (not anti-cavitation plate) being "level"?

What's more important is where it is compared to the water - it should skim over the top while zipping along.
 
Do you use your Grady in the Ocean?...if so, why is top speed of 50 MPH important?
You will hardy ever have Ocean conditions where you can run at full throttle for any significant period of time anyway...

What IS important for the long-term health of your motors is that your props and set-up height allows your motors to reach the manufacturers' recommended RPM levels at WOT, regardless of what speed that happens to be.
 
My guess is the engine and prop are performing correctly. Another guess is the boat has a decent hole shot which I considered more important than wot.
Since you’re close to 50 anyway, pick a day during a king tide, mid-tide, run with it for your high speed run.
Or, change prop pitch for more speed and take a few more seconds to get on plane.
 
The big detail I overlooked in the OP was comparing performance from a 3.3l 250 to a 4.2l 250 The 4.2 l has a ton more torque and I'd expect it to perform a bit better than a 3.3l. The difference between 48 and 55 can probably be explained as the apples to oranges comparison of the two motors.
 
Anticipating that you can spend a lot of time and money for small gains trying different props. You do have an older motor, might not be delivering a full 250hp.

I’d reach out to Prop Gods for a specific reccomendation for a different prop or with a local prop shop for some custom modification of your current wheel (do it to the old one) to gain more boat speed. Improvements will likely be at the expense of other performance parameters (hole shot, low speed planing, midrange fuel burn) but you should have some flexibility as there is reserve power with 250hp on 205.

After that it’s water conditions, hull condition, motor height, boat load, engine output, fuel quality. I am pretty skeptical of real world max speed ratings over 50mph on a 205. Presume you are using GPS.
 
Scrub the hull, run low gas tank level, remove all the junk from the boat, don't eat breakfast. Now go for a run and ley us know what the top end is.
Seriously though, I am wondering if this post is a prank:p.
 
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Considering the max rated HP for that hull is 230hp, putting a 250 on it sounds like a solid idea to eke out a few more mph. Who cares about keeping control of the boat or damaging the hull...


</sarcasm>
 
if you claim to replicate the top speed of a "performance report" with a 20 year old boat with a smaller motor then id call you a liar.

those reports are usually BS to some degree. sounds like your properly pitched and your boat is fine the way it is....your boat is not a 50mph boat, sorry
 
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