F300 Repower - Early Observations

[wahoo33417]

Just had my 2005 F250 replaced with the new F300 on my Journey 258 today. After only four hours towards break-in, here are some early observations while running in the calm ICW followed by a few cell phone photos. Numbers are from Yamaha guages:

Definitely a bit more power and better fuel economy. The sweet spot for my F250 was 4,000 rpm, making 27 mph and getting about 3 mpg. Now I get 27 mph at 3,400 rpm, getting 3.4 mpg with 4/5 fuel. Sweet spot seems to be 3,300 rpm, making about 25 mph and 3.5 mpg. 4,000 rpm now makes 33-34 mph. I touched 5,000 rpm only briefly today and saw 41-42 mph. Don't know yet whether my prop is just right as I have not opened it up.

Digital throttle and shift: Yup, everything Yamaha says it is. No matter how many times the dealer said 'be careful' on that first push of the throttle ...
Fortunately, I was pointed away from the dock!

Sound: A bit louder, I think, both when coming up on plane and while on plane. Not significant difference, but it is a different sound.

Only negative experience so far is that the added power carries over to more 'torque steer' while on plane. Takes more effort to turn to the right than it does to the left. I have not yet played with the trim tab and that may cure that.

While the boat was in the shop I also had them flush mount my Garmin 4208. I asked them to fit a piece of starboard to same size as radio box door and mount from there. They did a nice job, in my opinion. Last photo is with the old radio box door in place, for comparison.

I'll post more in the coming weeks after I get some experience, post break-in.

 

[magicalbill]

This is a great example of how increasing your HP can result in better economy and higher speed.
There are many who automatically assume that less HP = less fuel burn.
Plus, the engine works less to achieve better numbers per a given RPM, which translates to longer engine life.

I suppose there are exceptions on certain hulls. I read on here guys running 225's on Marlins and Expresses and getting better numbers than the 250's.

I have twin 200's on my Gulfstream and the Grady perf. specs say they do better than the twin 150 combo.

Good stuff Wahoo..

 

[SteveS]

I have a Grady 258 Journey and thinking about repowering with the Yamaha V6 F300. I am very interested in your testing results.
Does your Grady 258 have a hardtop and curtians ? Is it bottom painted. I know that these items will affect the numbers. On what hole on the engine bracket is it mounted ? Thanks for your help. It looks as if the F300 is the right choice for my situation.

 

[Ed Bukala]

Hi There
Our Freedom 255 shares the same hull with the Journey 258 as you know. We have the 300 hp on her and I was surprised to see the performance numbers you are initially seeing. Our 255 has the hardtop and the engine is mounted in the second hole from the bottom with 2 holes above that it can still go down. The best numbers I saw this summer were 2.5 mpg @ around 4,000 rpm with speed of 25-27 mph. Top speed we saw was 41-42 mph. We have no bottom paint on our boat. As I have mentioned on previous posts, I can only get 87 octane gas in our area(no trailer) are you using the recommended 89 octane?
Bukster

 

[wahoo33417]

Ed & Steve: I've not been back on the boat, but can answer some of the questions. No bottom paint and no hardtop. I do have an oversize bimini (6' long) and it was up. I'm not sure that the bimini doesn't add more drag than a hardtop. The bimini is billowed out while running no matter how tight the straps are.

I don't know which mounting hole its on - I'll have to check this weekend. I do burn 89 octane. There is no 87 on the water in our area.

My 2005 hull was advertised as being 4,150 lbs. I think the newer versions are heavier, but that wouldn't seem to make that much difference.

I'm reporting from the Yammy gauges which I'm assuming are about accurate. I won't really know until after going through a full tank or two or making a long run.

Below is a photo of boat running back from Bahamas that shows the drag of the Bimini top. Click on image to enlarge:

 

[wahoo33417]

Ed: I may see the difference between your numbers and mine. I'm guessing you have the 15 3/4 X 15 prop. The table below are Grady's numbers with that (recommended) prop:

Performance Data
Test Date: 10/8/2010
RPM MPH GPH MPG Range dBA
FALSE 1000 5.1 1.2 4.21 624.9 61
FALSE 1500 7.0 1.9 3.66 543.2 67
FALSE 2000 8.4 3.0 2.78 413.3 73
FALSE 2500 9.0 4.4 2.06 305.5 76
FALSE 3000 9.9 6.2 1.60 237.8 81
FALSE 3500 13.7 7.7 1.78 265.0 83
FALSE 4000 28.3 11.3 2.50 371.9 84
Cruise 4200 29.8 12.0 2.48 368.2 84
FALSE 4500 32.2 15.0 2.15 319.3 88
FALSE 5000 36.6 18.1 2.02 300.7 89
FALSE 5500 40.7 22.9 1.78 264.5 90
FALSE 6000 44.1 26.1 1.69 251.4 92

Idle to 30 MPH: 9.22 sec.
Seconds to Plane: 5.25 sec.

I have the 17 1/2 X 17 prop. Grady recommends the smaller prop. But my dealer recommended that I try the larger. They will swap it out if I'm not satisfied. But I can confirm that I'm making 27 mph at 3400 rpm and getting 3.4 mpg. I can squeeze out 3.5 mpg if I drop down to 3300 rpm, but speed drops to 25 mph. The engine has only 7 hours, so maybe this can get even a bit better with 100 hours.

However, at WOT throttle I'm only seeing 5600 rpm but it is at 47 mph. Drawback is that above 30 mph or so, I start to feel torque steer (perhaps not correct term?). The boat is harder to turn to starboard. Not so hard as to be a problem, but it is noticeable. I rarely run more than 30 mph for any distance, so I'll see if I can live with it. Maybe I'll add Seastar power assist - for the wife, of course.

My engine is mounted on the second hole from the top, fourth up from the bottom. My boat is probably as light as a 258 gets, since I have a bimini top and don't have the auxiliary fuel tank. Bottom is not painted. It may be that the 17" prop is too big for most boats that leave the factory. But since my dealer will swap it out if need be, I'm going to stick with it at least until the 20 hour service and decide then.

Rob

 

[Bob Coco]

Wow, That's a nice looking engine. I would love to have a pair of those on my 283. Hey you can never have a boat too fast. lol
I have to say that my 283 w/ 250's is way better on fuel then my 282 w/225's was. I know there different but the hulls are exact and weights are very close.

Enjoy all that extra throttle. I know I would.

Regards, Bob

 

[Ed Bukala]

Hi Waho33417
Thanks for the update and additional information. Bukster is put away for the winter but I have a spare prop and I went down to the basement to check it out and guess what, you are bang on, it is a 15T 15 3/4 Yamaha Saltwater Series 11. I am definetly going to talk to my dealer about this as the differance you are seeing to my numbers are huge. Yes I do have a hardtop and can only get 87 octane fuel but with 2.4-2.5 being the best I ever saw and usually 2.1mpg there obviously is huge potential for improving this performance. Gas up here in Canada runs at $5.50 - $5.60 per imperial gallon which equates to about $4.50 per US gallon so even getting .5 extra mpg would pay for the cost of a new prop likely in one season. I will keep you posted.
Bukster

 

[The Black Pearl II]

I have a 360 with trip 250's getting better fuel economy is going to be the name of the game going forward. I had a great conversation with power tech prop's and suggest you contact them. they have a great web site that you can request info on a prop. you guys are trying to get to 2.5mpg, I am getting .85 and considering change 3 props to get to 1.0 (don't know if it will work).

 

[NOTHING ELSE MATTERS]

Black Pearl, before you lay the dow for the props, see if you can borrow a set first to try, but i really don't think is gonna change anything, if you decide to go with 4 blade props, you might see a little difference on MPG on cruising speed(it might be a little less than what you had though), but your top end will be less.
Also, 4 blade props tend to lift the stern, so you'll see a difference on the handling also. I also was looking to change my props and i talked with guys that make propellers and told me that i will not get any better numbers than my 1 MPG. I get 1 MPG at almost any speed, except WOT.