Grady 330, f300 outboards best mount height and propeller type and size

[Stevenwest]

Engine mounting height plays a enormous role in speed/performance as does propeller style, pitch and diameter. many times engines are mounted too low.

I am purchasing a 2004 330 with 2014 f300's and it isn't performing as well as expected. the engines are mounted in the #1, top hole, lowest engine mount position with Yamaha saltwater series II 15T x 15 3/4 propellers which = 15" propeller and 15 3/4 pitch.

The boats performance 1/3 fuel, 3 people

4000rpm 23kt/26.46mph
4400rpm 25kt/28.76mph
4500rpm 26kt/29.6mph
Full Throttle
5800rpm 34kt/39.12mph

I have seen threads with 250 hp outboards that show equal speed vs rpm and with 300hp engines I would expect even better so ai am suspecting error with engine height and propeller size/pitch.

There is a thread here from a owner with f300's that says:
"I cruise at 29-30 MPH at 4400 RPM, burning 1 to 1.1 GPH. At WOT, top speed fully loaded is 42-43, MPH."

Also I have seen some threads of people with 17 ' pitch props saying they get better performance. I use a 4 blade prop on my 16 whaler and it outperforms the 3 blade.

This youtube video shows a repower with f300's and they rave about improved speed. In the video you can see they mounted the engines at the #2 hole which is one hole up in height. Unfortunately they don't have speed specs, and also don't show propeller information.

I called Yamaha and they don't have a performance sheet for a 330 Grady with f300's and I am awaiting a response from Grady to see if they can send me any old performance sheets that they no longer post on the website. They must exist.

Please if you have a 330 with f300's let me know your performance , prop brand, type (3 or 4 blade), size and pitch, and your engine mounting position/height.
It will help me find out what performs best and will be then available for others in the future when they repower.

 

[Automated14]

You won’t find many, if any, factory performance reports for a 330 with f300’s….best you will do is what you already did- seek out others with repowered boats. Seems the 330 went from 3.3l 250’s, skipped the 300, and went straight to the F350v8.

with that said, I have noted a few things during my prop selection after repowering my ‘04 with merc verado 300’sAs much as I love my v8 torque, I feel like you should get similar performance out of any of the 300’s currently available .


- I asked all over and could not find anyone running a 330 with Yamaha or merc 300’s who’s running 15 pitch props.
I tried 2 sets of 15’s. Power techs and mirage. Powertechs blew past redline. Mirage the rpm’s perfect at 5900:but no bite and 39 top speed. It felt like no bite.

-after a disappointing test with a set of turning point 17’s, I went for the Enertia eco 17’s. Nailed it. Redlines about 5900, top speed 43. I can cruise 4900/35mph/1mpg or 4500/30mph/1.3mpg.

-note that my engines redline at 6k, think yours are higher.

-note that my engines have 1.85 gearcase, I dont know what you have.

-I’ve heard from 2 other guys with verados and a lady with Suzuki 300’s who get even better numbers than I do.
as far as I know, I’m the only one with the engines mounted as high as possiblle. I struggle this as my anti ventilation plates look to be at perfect height on plane yet the others get better numbers than I.

- I believe that not all props are created equal. I tried 2 different sizes and even with the size that didn’t work out, mercury’s were flat out better performers.

I did find a set if used rev4’s. That was a conundrum. The boat handled better at every speed but performance was off by lot despite getting close to redline at WOT. They come of a 30 Marlin with yam 300’s and looks like they were modified. I’m going to take them into prop guy this winter and see what he can do.

 

[wspitler]

GW has a Yamaha 300 performance report for the 330 Express, I don't remember how I found it on their website, but I'm sure they can dig it up for you. I used that bulletin in 2021 to get the same prop (SWSII 15 X15 3/4) that they put on the boat when it came standard with 300s. I repowered my 2007 330 from the F250s to the 300s in 2021. (no bottom paint) I tried the 17" pitch that was standard and came with the F250s and it seemed my WOT RPM was a bit low, so I changed to what GW recommended back when they put the 300s on the boat. The older 3.3L motors like the F225-250 had a different lower unit gear ratio than the newer 4.2L motors. My motors are mounted in the top hole and I get 26 knots at 4400 RPM and about 1.0 NM/G. I can get 1.1 sometimes 1.2 NM/G in perfect conditions at 4200-4300 RPM with medium loads. I think the 17" pitch props may get a little better NM/G, but WOT RPM was in the lower range of acceptable to me (5400 at medium loads, 5200 heavy) Hope that helps!

 

[fsc60]

This is my old post
After 4 seasons i wouldnt change a thing
Motors are mounted in top hole

Sep 17, 2020

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• #9

I just bought Power tech OFS4 15.25x15 pitch 4 blade props in June
They are on new Yamaha 300s which are on my 2001 3300 Express boat is bottom painted
I am still breaking in the motors, but by the weekend i should be able to open them up, boat is full of fuel and water.
I can tell you this, we went out for a ride, 11 people, 4200rpms and we were at 32 mph
It felt like it had so much more
After Break in 5500 RPMs at 40 mph, my Yamaha Dealer thinks that if I try to get more RPMs with a different prop I will probably over Rev.
This combination works great, i can stay on plane as low as 3200 RPMs
They bite great, She pops right out of the water, reverse is no problem,
I typically Cruise at 4000rpms at 30 mph with a 1.1 mile per gal thru anything,

2001 330 Express
2018 Yamaha 300s

 

[Stevenwest]

Bert Kelly from Grady White did send me a 2010 performance spec sheet for a 2004 330 with f300's. The engines were mounted in the #1 hole = lowest position. The sheet shows better performance than I am getting. It showed a top end 44mph, best cruise at 4200rpm 29.9mph at 1.25mpg 32.9mph at 4500 rpm. The Yamaha techs repower of a 2004 330 with F300's over the original 250's shown in the youtube video said their re-power showed a 30% better 0-30mph aceleration, 50% better cruise speed at 4000rpm and 29% better mpg at 4000rpm. the video doesn't give actual numbers or prop info. I am curious about the performance numbers of the Yamaha boat with the engine mont position one hole above the Grady white test boat. Does anyone have a 330 with F300's mounted one hole up?? thanks

 

[Stevenwest]

Thanks guys for the info so far added to the post

 

[everwhom]

I have an '03 330 Express with 4.2L F250's which are the exact same motor as the F300's but with a detuned ECM. Your performance is almost exactly what I get on my boat. I would think trimming out would more or less make up for being mounted 1 hole too low (unfortunately I can't tell you how my motors are mounted until next Spring), but I agree something isn't quite right.

Here's a funny thought: is there any chance the previous owner put F300 stickers on F250 motors?

 

[Stevenwest]

Its true that there is more boat owners than you would think who fake their engines with different decals. I would doubt the prior owner would ever do something like that. It is funny to see like a scarab in Miami for sale with 450HP decals and then in the ad it says 350's with 450 decals ........ in other circumstances I may be more upset but in these cases I am a little sorry for the guy and think ...well now I know who has small pen!$.........

 

[Sardinia306Bimini]

Here's a funny thought: is there any chance the previous owner put F300 stickers on F250 motors?

Yes that is possible.

To check what you have then
a) have a mechanic reading the ECU with YDS
b) under the rear panel is the ECU, check the numbers there, particularly the VER nn.nnn, this is the HP version

I got my F250 sold as with 300 hp ECU by original owner but a few days ago I checked the ECU number and it seems to be a 225HP
The wired thing is that my power is similar to the one my buddies have with same boat and F300 and run same propeller, and engine document show 250HP as well.
I used the Suzuki 16x18.5x3 Propeller and engine could not turn it more than 4200 rpm and I was surprised that the 1/2 inch diameter made such a big difference.
while with Yamaha Saltwater 19" motor turned 5300 what is how my rib get rigged and delivered.

Below you see my ECU and VER. 6CL-21 what seems to be the 225HP ECU
Next season I need to address that...




Chris

 

[Gulffisher]

My 05 GW 330 Express wants to be trimmed high out of the water for best speed and fuel economy. During your testing, did you trim engines up to slipping and then back down just enough to where slipping stops? If not, I suggest you try again with more up trim.

Sorry I forgot, and no tabs...

 

[Stevenwest]

My 05 GW 330 Express wants to be trimmed high out of the water for best speed and fuel economy. During your testing, did you trim engines up to slipping and then back down just enough to where slipping stops? If not, I suggest you try again with more up trim.

Sorry I forgot, and no tabs..

Always working to try to tilt the engines to try to get the sweet spot for best performance/push angle-height. I'm still just wondering why the Yamaha techs mounted their f300 engines at #2 hole = 1 up vs the grays performance sheet of all the way down #1 hole and if it gave better overall performance so still seeing if anyone has their f300's mounted one up.

 

[Stevenwest]

Always working to try to tilt the engines to try to get the sweet spot for best performance/push angle-height. I'm still just wondering why the Yamaha techs mounted their f300 engines at #2 hole = 1 up vs the grays performance sheet of all the way down #1 hole and if it gave better overall performance so still seeing if anyone has their f300's mounted one up.

gray white- not grey

 

[Stevenwest]

gray white- not grey

what is up with my computer?? GRADY-WHITE not grays

 

[Gulffisher]

My 05-06 250's are mounted as far down as they will go. Top bolt in the top-most hole and bottom bolt against top of lower slot. I cruise around 30 MPH at about 4800 RPM and burn about 29 GPH. I don't push the old engines too hard anymore so 38 MPH is about tops for me in the low 5000's and around 40 GPH. I forget shaft length but factory original install. Do you have extra long extended shaft length?

If you can borrow test props, I would test several props and calculate slip from idle to WOT for each one, and see if you can find the one with least slip and closest rated WOT. Then I might worry about mounting height (again, assuming normal long shaft), but not too much because that is a big heavy boat and I just don't see an inch or so of mounting height making huge difference (nothing simple engine trim can't accomplish).

Also... Someone above suggested you confirm you are purchasing 300's. I assume you checked serial numbers, casting numbers on block/parts etc., and checked compression and did leak-down cylinder tests? While much newer than mine, those engines are not exactly new and may have been abused/overhauled, etc.

 

[Sardinia306Bimini]

I know that a lot of high volume riggers install the engines a hole too low to avoid complains with ventilation, particularly in tight turns.

However, the hole thingy I s half a myth for rec boaters, but true for race boat drivers where microseconds count.
I had hydraulic jack plates on my twin DF300AP powered Venture 34 and the difference between all down and all up was marginal for normal use.
But this was on a 34ft boat, too low mounted engines on smaller hulls can lead to porpoising even if that is mostly wrong weight distribution than the wrong height.

Much more effect has a propeller/s, mounting the right one to solve a "problem" will do the trick much better, 4 blades for example and/or stern/bow lifting ones.

I checked a 2006 330 a few weeks ago and it had the usual Saltwater II props but I guess this big and heavy boat would be much more economic on cruising speed with the right 4 blades, but would loose a few MPH's top end speed. I personally are more interested to be able to cruise more fuel efficient at 3500 rpm around 30 knots than max speed as I rarely go top speed.

Chris

 

[Flot]

I'm on my second set of F300s on my 2001 330.

When I bought the boat used, the props were Quicksilver Thunderbolt 15.5x17p. Cruise low 30s, WOT 42-44, generally 1.0-1.2 mpg on plane.
When I repowered, I kept those props for a bit and then moved to a set of Powertech L3 15 3/4 x 15. Boat handles a little different, but seeing 1.1-1.2 more consistently, WOT still around 42-44.

I am a big fan of Enertia Ecos, which the L3 props seem to be knockoffs of. I just wasn't able to find a decent price set for testing.

Remember that with a relatively "slow" boat like the 330, current, wind and waves matter. The only way to get good results is testing a run in opposite directions and averaging it out.

Despite the motors working hard, the F300s are a great fit for this hull IMO. With a light load, it hops up on plane shockingly well for its size.

 

[Fido]

We repowered an Express 330 with twin Yamaha 300HP DES, helm master etc earlier this year.
I studied many express 330’s with regards to engine height. Having had 2 x Marlin 300’s and having played with engine height before from my experience I can attest that Grady’s perform better with the engines mounted lower than what might be considered normal.
We mounted at the lowest possible height.
We get 40knot top speed at 5600-5700RPM lose about 1-2 knots with a full load of fuel, water, ppl and gear.

 

[HMBJack]

I repowered my 2006 330 with DES F300's built in 2021.

Using PowerTech OFS 4 blades in 16 pitch. WOT reaches 5,800 RPM's.
I cruise comfortably at 28 knots 4,300-4,400 RPM's all day long.

I tried a set of PowerTech OFS 4 blades in 15 pitch and didn't like them.
The 15 pitch had me at 4,700-4,800 RPM's at 28 knots which was too high in my opinion.

With the 16's that I have, I feel I get the best combination of torque, economy and speed.

My F300's are mounted high - in the third hole from the top which I like since my boat sits on a HydroHoist Boat lift (transom goes under water when lowering the boat).

I get little to no cavitation and simply need to trim the engines down on take off then trim them up once on plane. Hope this helps!

 

[Automated14]

We repowered an Express 330 with twin Yamaha 300HP DES, helm master etc earlier this year.
I studied many express 330’s with regards to engine height. Having had 2 x Marlin 300’s and having played with engine height before from my experience I can attest that Grady’s perform better with the engines mounted lower than what might be considered normal.
We mounted at the lowest possible height.
We get 40knot top speed at 5600-5700RPM lose about 1-2 knots with a full load of fuel, water, ppl and gear.

could this be because of the deep v at transom with the large spread between the engines?

 

[Fido]

I wish I knew. Having them higher would help with clearing the tips of the gear cases when full of fuel and water.
The Marlin didn’t gain any performance with engines higher but the boat didn’t feel as nice coming on plane as with the engines down.
Just my feedback anyway.