Grady says F350 not suitable for pre-2008 boats

[wahoo33417]

I received a fax from my dealer today that reads:

Important: Product Advisory - Repowering non-current boats with Yamaha 350 hp engines.

Please note this follow up to information recently shared with you by your Regional Sales Representative.

Structural and flotation changes were made to our 2008 boat models to accomodate the weight, torque and horsepower of the F350 Yamaha engine. Due to these factors this engine will not be suitable for the repowering of boats built prior to the 2008 model year even if previously rated for 350 horsepower.

Rob

 

[gradyfish22]

Thanks for the info Rob, I know many have considered this upgrade but many did not realize that this change could not be made. I've been telling many this before both here and on other sites, but not all have agreed, it is good to hear it from Grady.

 

[DBV]

I wonder what changed on the 08 275 that would allow it have a single 350 on it?

 

[Tashmoo]

I was told that the transom design was beefed up to include an aluminum plate or strut (can't remember the exact wording) additional fiberglass and I think more wood. I was also told that the 275 was the only boat designed for the single F350 when they came out (certainly the larger boats were designed for the twins and trips), I do not know what year the 275 model was introduced 2007 or 2008? If 2007 the question on this model is up in the air.

 

[blackdiamond296]

I was also told that the 275 was the only boat designed for the single F350 when they came out

I dont know about that- there were a few other grady's on display at the NYC boat show with a single F350 on them.

In regards to the design accommodations for the F350 they did beef up the I -beams in the transom and the glass work, they also increased the thickness of the glasswork in the bow along the centerline to compensate for the increased pounding the boats will take from the extra hp and speed
:shock:

 

[Kenlahr]

I was recently on a Gulf Stream with a single 350 (2008) at the dealer.

 

[wahoo33417]

According to Grady, the 2008 models 232, 257, 258, 273 and the 275 discussed above are all okay with the F350. The change is the laminate schedule and additional aluminum bracing others have already described.

Rob

 

[go fish]

I was informed that the F300 also applies as it is the same weight with tons of thrust.

 

[BobP]

For older boats with twins rated 400 or more total who want to go to one F350, I don't see a problem since the F350 is lighter than the twins, just need to add transom plates IMHO to spread out the forces laterally to cover the area spanning across the former twins on the transom. You may not be able to fully tilt the engine out of the water, but so what, ever own an I/O ?

Guys with Grady Drives can replace the drive with one with a deeper setback and proper single rating, check with Armstrong. You will see such a Drive with an F350 on it in the Yamaha engine catalog, on the stern of Parker pilot house.

 

[gradyfish22]

As mentioned above, to handle the loads there is a new laminate schedule and the stringers were beefed up near the transom. It has nothing to do with overall weight or hp, it is where and how the load is applied. To be able to accommodate the F350, one would need to totally redo the transom and beef up their stringers, even older bracketed models cannot do it, changing a bracket will help, but stringers and transom work is still needed, but might be slightly less. The transom was designed to handle a load of 400hp total, spread over a large region, reducing that region and applying it to a smaller portion of space will increase the needed thickness and strength of the transom. Adding a transom plate only spreads the load over the transom, but does not strengthen the laod applied to the hull through the stringers, and does not fortify they transition from the transom to the hull bottom itself where much strain and stress occurs during pounding. Also, many newer boats had running surfaces or complete stringer redesign's to accommodate for higher speeds and greater forces applied to the hull from pounding while underway, some models may be strong enough, but not sure which, not a risk anyone should take. Unless you plan to get into a bit or transom and hull work, I would not consider an F350 on an older boat, and even then it is a big risk that I would and I know Grady White does not recommend. If modifications to accommodate an F350 to older models was an easy job, Grady would tell you that, but they have stated many times that they DO NOT recommend it.

 

[BobP]

Any twin rated 400 or 450 rated transom can handle the F350 by spreading out the forces mimicing where the twins were. It's exactly what a grady drive does to a Gulfstream be it single or twin drive. The stern and every connection to it doesn't know the difference.

Don't overestimate the bloated F350 because it's 800 lbs, that block has to be good for 400 HP or more in another incarnation. Suzuke did 300 Hp in 600 lbs, no way the extra 200 lbs was needed just for 50 HP more.

The F350 engine bracket is already wider on the transom than any V6, much wider.

If I replaced the drive on my 252G with a single rated for the F350, vs. the 400 HP worth of 2 strokers I have now at over 1000 lbs, my boat's stern and it's attachments will be on holiday.

Grady found another sales pitch for new boat model push, that's unfortunate especially for the 33 Express 2007 and prior, in need of the twin F350s - get them up in the mid 40's at least and look proportional back there. They have no other 4 stoke choice now except for converting to Suzuke to get 600 HP, as well as any other single rated 300 HP transom model 2007 and prior.

 

[Brad1]

It'd be interesting to hear specifically what was done to accomodate the F350. I know Grady was already incorporating a 5/16" aluminum angle into their transom core that the top motor bolts went through (I'm referring to what's inside the transom, not that aluminum trim they use to cover the gap between hull and liner).

A few months ago, Trailer Boats magazine did a review of the F350. For their review / test, the F350 was mounted on a Grady 257.

 

[Grog]

I need more info to calc the static weight difference difference between the 350 and say twin 200's. Take a boat with a bracket, the two engines push against the bracket to move the boat. As long as the bracket is rigid enough and not deform, the force on the transom will not change if you push in spots where he twins are or in the middle. Your standard bracket is not designed to take 400 HP pushing in the middle and things may get ugly. Your ride may not be that good because there is a lot of weight further back from the transom.

If you have the room for twins and have a hull that needs 350HP why go with the single? The bigger boats are much easier to manuver with the twins plus you have redundancy.

Who in their right mind is going to buy the Yami 300 at 800 pounds?