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I have a Grady White Voyager 24', Weight w/o engine about 4000 lbs.. I plan to repower with either twin Yamaha 150 4 stroke, T150 Yami HPDI , or Single Yami 300. I can't find info on which combination will give the best torque, mph and mpg. Anyone know?
Thanks, RC (dija)
I don't know what sort of activities your into...but if you can live with cruising in the low - mid 20's you'd probably be a great candidate for a F225.
Quiet, Efficient, no 2 cycle oils. For me that would be the only way to go. It is not very often I need to or can go 40 knots.
Thanks, Harpoon. I normally go to reefs about 20 miles off SC coast. Don't care about speed unless chased by squall. Want excess power for rough weather.
Gradys web site has links from the 258 model (the same or similar to your boat) to performance data with a twin 150hpdis, single 225 four strokes and a 250hpdi the 257 model (a center console vesion of the same boat) has test for twin 150 four strokes.
I just ordered a Grady 258 and choose the twin 150 four strokes. The single 225 four stoke was too weak mid range and a single 300hpdi was a close second choice for me.
Hello,
I purchased a 24' Offshore. The hull was made in 1983. I'm not certain of the length or width of your 25' grady but it is heavier than my boat. Grady sent me the original brochure and specs. My boat empty weighs 3200lbs without fuels or motor.
The hull has a max rating of 280hp. I purchased the boat with an evinrude 200hp 1993 ocean pro motor. Great motor. I found I could cruise at 24 mph at 3800rmp and WOT 36mph.
In a following sea, the waves tossed the back end of the boat around. Also, when those giant SC thunderheads form and the skies blacken I found I was wishing I had some extra speed in running away. Or circumventing the thunder/lightning cells.
I took off a perfectly good motor (that evinrude had only 250hrs on it and ran great) and replaced it with a brand new 2001 hp Yamaha efi. A dealer had several left over from two years ago.
Now the boat runs 42mph at WOT 4900 and cruises 4000 rmp at 32 mph. More importantly, it handles much better in following seas. I don't know if I will ever need/use the extra 6 mph to outrun a storm, but I'm glad I have it.
The 250 consumes much more gas than the 200hp motor, but I've never saved money operating a boat under any circumstances. It's a big and mighty ocean out there, and I do not regret at all the extra power.
Find out your max hull rating. Your insurance company will cancel your coverage if you exceed it. Be very careful when considering any hp under 250. Grady make's a substantial boat. I'd suggest you get to 85-90% of the hull hp rating. Even 20 miles offshore is a long way if there is a storm between you and the jetties.
I made my decision to upgrade after outrunning a thunderstorm with my kids aboard only 15 miles up the Wando and trying to return to the Ashley marina. Just barely outran the storm (light rain and winds with black sky approaching)with the 200hp evinrude. And that was inshore. The South Carolina low country has vast inshore reaches of water.
Finally, I'd strongly recommend you call Grady White directly. I've had great service with having my questions answered from their customer service rep's. Be mindful that this is with a 20 yr old product that's been out of production for 12 years. The fellow even called me at home on his nickel long distance to make sure all my questions were answered completely. And I purchased the boat from a private party. The Grady rep will also be very helpful in determing whether you should hang two heavy fourstroke's off the back. (He strongly recommended I shouldn't.) The Grady's made in the 80's and 90's never had the four stroke's in mind.
dssmith had some great info in his post but the new Yamaha 150 four strokes are lighter than the 150 two stokes. (the four strokes are 4cyl in line and the HPDI are cut back V-6s)
NJ208 is correct. Here's some info from the Yamaha and Johnson websites to consider
150Yamaha 4stroke 466lbs 25"
150Yamaha HDPI 475LBS 25"
150Yamaha VMAX HDPI 468lbs 25"
150Yamaha 2Stroke 426lbs 25" (non-HDPI)
All 2004 models
Johnson 150hp 4Stroke 425lbs 25"
Johnson 150HP 4Stroke 417lbs 20"
Johnson 140hp 2 stroke 391lbs 25"
Johnson 140hp 2 stroke 383lbs 20"
So you can get a lighter 2stroke Yamaha but it won't be HDPI. And Johnson's are even lighter.
And only about 550 pounds for the 300 hpdi, less drag, probabaly less maintenance costs, but it is a 2-stroke. Should be faster than twin F150s or any other single.
Twins cost more, weight more, consume more fuel and usually are slower (more drag caused by the second leg).
Having said that, the Mar 2002 issue of Trailer Boats Magazine did a head to head comparison of a pair for F115 versus a single F225 on a Seaswirl Stripper 2301. All of the above statements were true except the twins had a better top speed by a little over 3 mph.
Twin look cool, and they do have additional saftey issues if your going a long way off shore (especially is you have separate fuel tanks), but the maintenance on a 4 stroke will make you cry. Ask your dealer what an oil change and filter costs on an F150 and how much is a valve adjustment.
Personally, I'm not a big fan of Yamaha's HPDI technology; too complicated. I would probably take a 4 stroke over a HPDI even with the higher maintenance costs.
Here are some prices from Ed's Marine (dssmith, you have your hp ratings on the Johnson's backward; everthing else is correct)
Twins vs Single 
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