1998 Gulf Stream motor weight - deck drains water height

[Hamish]

Hello there all GW members .

I am the proud owner of my first GW and I have only taken it for a test drive on a calm day and I will be collecting the boat in 2 days time.

It is fitted with a pair of 2006 25 inch verado 150 hp four strokes.

My initial thoughts was:

- it feels a tad underpowered and

- I’m surprised it comes off a plane around the 20knt speed (I’m wondering if that’s a function of a bolt on engine bracket shifting the motor away from the end of the planing surface of the hull)

- I am wondering if the 4 rear thru transom deck drains are supposed to be exiting the boat bellow the water line at rest?

I also have a pair of 2014 yamaha 4.2 v6 250hp 25 inch motors not being used so I contacted my marine engineer who said that supprisingly the pair of larger Yamahas would only weigh an extra 55 kg as compared to my current 150 Merc’s and to maybe perform a test of sitting some one of that weight ontop of he existing motors to see what that extra weight does to the height of the swim platform at rest relative to the water line ( he wasn’t really worried about the extra hp fyi )

The purpose of this message is to see what people think about:
- me fitting the pair of 250 yam motors for a bit more power and wondering what that would do the slowest planing speed ?
- checking on the design height of the 4 thru transom deck fittings as they currently appear to be about 1-1.5 inches bellow water line at rest with only *200L of fuel in front tank and *60L in the rear tank ( I believe it can take 335 / 340 L for the front n rear tanks respectively if 100% full)

looking forward to your Feedback

the attached photos was with the above mentioned *fuel load

 

[DennisG01]

It's hard to tell from the angle of the photo, but the boat appears to sitting pretty close to level with the bow just a bit high (which is proper).

Twin 150's should be pushing that boat along VERY nicely. Having the motors on the bracket INCREASES performance, including hole shot.

Is this your first boat? Are you trimming properly at lower speeds? You'll need to get those engines tucked in to keep from falling off plane at slower speeds. You might want to use your trim tabs, as well - they will make a HUGE difference.

 

[Hamish]

Hello D
I have had a few boats and been in quite a few. I’ve never owned one of these and or a boat of this weight. My concern is that it was running very light so to speak that day and just thinking how it will go when realy loaded up with the small twin 150s

 

[CharlieBeard]

I have this same year with twin 150s yamaha. I just got back from week-long fishing trip. 150s pushed us along great. Fully loaded with 180 gallon fuel, four 160 quarters cooler full of ice and cases of beer and it Popped right up on plane. Cruised at 26 knots burning 17 gph. Dunno how fast you like to cruise, but that's the sweet spot for me in PNW where there is lots of driftwood in water. For me personally I'd only go bigger to get better fuel efficiency. Min planning speed is 3700 rpms...I'm thinking that is 17-18 knots iirc. Rear drain is also under water...I don't like it but it is what it is. It drains fine and I have had very few times that I get wet deck.

 

[CharlieBeard]

I run four blade props of 15 degree iirc, so that may be factor in getting out of hole when loaded. Engines run 6000 rpm at Wot so I could probably prop up to get topend speed, but I like easy holeshots. Boat is rated for 350 hp. I dunno what that does for insurance if you exceed max rating, maybe someone online here can inform us. I was told the boat was designed for 2 strokes. I have 2006 4 strokes. ( and 9.9 kicker). I don't love the way it sits in the water. Feels a little low, but I've learned to accept that. I'd image 250s would put even more weight back there. Good luck!

 

[CharlieBeard]

..and bigger motors would only hurt min planning speed. More weight in back. Trim and tabs might help. Props might help too as i am told the four blades help keep ass end up, but i bought with gour blades so i dont know i don't know what it was like before

 

[DennisG01]

Hello D
I have had a few boats and been in quite a few. I’ve never owned one of these and or a boat of this weight. My concern is that it was running very light so to speak that day and just thinking how it will go when realy loaded up with the small twin 150s

It might just be that you have to get used to a "bigger" boat and they way they perform. It's naturally going to be a little different than a lighter boat. The twin 150's are not really "small" - you have two of them with two props biting into the water. Twin 150's is a very sought after combination on this boat.

Can you respond to my questioning about trim and tabs? How are you using those? Did your other boats have power trim? Did your other boats have tabs? I'm tellin' ya, using those to things properly makes a world of difference! And, that's something you have to get used to that you may not have used nearly as much with a smaller boat.

Don't worry - you'll get it figure out. You just need more practice... which means more time on your boat... which is a good thing!

 

[seasick]

The added weight of the 4s motors and the kicker are causing the stern to sit deeper, hence the scuppers being underwater. You are not going to fix that with tabs. Tabe can help with trim and angle while under power and at speed just not while sitting. You may be able to raise the stern by adding ballast to the bow but that makes the hull heavier and that will affect performance to an extent as well as efficiency.
If the deck is not awash with water and passengers feet are not getting soaked, you can live with the scuppers being a bit low. When in reverse, you might get a lot of water, that depends on how well the flapper valves work.
One additional issue is marine growth on the scuppers. Being under water, they will be prone to growth like barnacles. How much and how fast depends on the seas you boat in and water temps.

 

[Hamish]

It might just be that you have to get used to a "bigger" boat and they way they perform. It's naturally going to be a little different than a lighter boat. The twin 150's are not really "small" - you have two of them with two props biting into the water. Twin 150's is a very sought after combination on this boat.

Can you respond to my questioning about trim and tabs? How are you using those? Did your other boats have power trim? Did your other boats have tabs? I'm tellin' ya, using those to things properly makes a world of difference! And, that's something you have to get used to that you may not have used nearly as much with a smaller boat.

Don't worry - you'll get it figure out. You just need more practice... which means more time on your boat... which is a good thing!

Hello Dennis.
Ans 1) - during the sea trail there was little use of the trim tabs other than once to show me how they push the nose down a bit and increase drag/ fuel usage a bit.
Ans 2) every boat I’ve owned had power trim n tilt ( on 2 of past boats I had to fit aluminium wedges between the transom and motor to provide more trim angle to keep the nose down)
Ans 3) none of my past boats had trim tabs.

my past boats are:
Southwind ub22, ub580 & a mackay 4.8 fortress.

I recently purchased a set of long zipwakes - I’m wondering if these are not necessarily a good thing to be fitting to the grady W in lieu of the original trim tabs ( I’m starting to think that they are more for auto leveling system rather than possibly how u are utilising you trim tabs to maybe assist in keeping the nose down at lower speeds / take off.

 

[Mustang65fbk]

Per the Grady White website, a brand new 232 Gulfstream with twin Yamaha F150’s on it will top out at 48.4 mph @ 6,000 rpm and optimum cruise is 29.2 mph @ 4,000 rpm and burning 13.3 gph of fuel, or 2.2 mpg. That’s plenty fast for me, of which my boat goes around 45 mph, and even that is plenty fast for me. Unless you want to go faster then I’d stick with the 150’s currently on the boat and, also per the GW website, the maximum horsepower for your year and model of boat is only 350 total hp. So… I think twin 250’s would be overkill and could pose a few more issues than might be worth the potential benefits. What is your speed/rpm at WOT? You might need to change props, as do a lot of people, as the previous owners oftentimes have ones that are the wrong size, blade count and/or pitch. If your WOT is only in the low 5k range, like say 5,300 with next to no weight or load in it then you’re likely needing different props to get you up near a 6k rpm redline with a light load. That way, when you’re fully loaded down you should still be in the low to mid 5k rpm range.

 

[DennisG01]

Zipwakes and Bennett hyrdraulic tabs (what you have) are both doing the same thing. Zipwakes are newer tech and do it quicker, is all. But both will level the boat side to side (list) and fore/aft (pitch). They will both help to keep the bow planted in a choppy sea. They will both get you on plane faster and stay on plane at a slower speed. They will both have less effect on fuel usage than trying to use the engines to control pitch/planting the bow.

My opinion... you should spend a season getting used to the boat and how to properly use the existing trim tabs, along with "learning" your boat, before you make any changes.

 

[Hamish]

I run four blade props of 15 degree iirc, so that may be factor in getting out of hole when loaded. Engines run 6000 rpm at Wot so I could probably prop up to get topend speed, but I like easy holeshots. Boat is rated for 350 hp. I dunno what that does for insurance if you exceed max rating, maybe someone online here can inform us. I was told the boat was designed for 2 strokes. I have 2006 4 strokes. ( and 9.9 kicker). I don't love the way it sits in the water. Feels a little low, but I've learned to accept that. I'd image 250s would put even more weight back there. Good luck!

Pics of props fitted 4 blade 17 pitch
When I take it out next I will get some concrete figures

 

[Hamish]

Pics of props fitted 4 blade 17 pitch
When I take it out next I will get some concrete figures

 

[Hamish]

Zipwakes and Bennett hyrdraulic tabs (what you have) are both doing the same thing. Zipwakes are newer tech and do it quicker, is all. But both will level the boat side to side (list) and fore/aft (pitch). They will both help to keep the bow planted in a choppy sea. They will both get you on plane faster and stay on plane at a slower speed. They will both have less effect on fuel usage than trying to use the engines to control pitch/planting the bow.

My opinion... you should spend a season getting used to the boat and how to properly use the existing trim tabs, along with "learning" your boat, before you make any changes.

Yes I agree Dennis