I am pretty new to the Grady scene and to date I have been keeping the motors trimmed all the way down and just using the trim tabs. In a couple of more recent forums I have noticed people talking about trimming the motors also to increase Revs etc. Could I get some advice please I am used to bigger shaft drive boats for offshore work?
Trimming the motors or use the trim tabs?
- Thread starter Absolute
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It is my belief that trim tabs on these boats are only used level port to starboard. Once you are up and running, use the trim tabs so the boat is level side to side, and then trim the motors up.
You will notice and sizable increase in speed and efficiency.
Tim
You will notice and sizable increase in speed and efficiency.
Tim
I am a hardcore trim tab user. I am a firm believer that you can get a superior ride out of any boat by having a firm knowledge of how your boat reacts to both motor trim and tab trim. Tab trims do WAY more than just port/starboard trim. MORE importantly they can control your bow entry.
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Start with your motors down and trim tabs up. As you come up on plane push the bow down with your tabs, then start to raise your engines. Your propeller will be at running maximum efficiency when you trim it up until you hear it cavatate, then trim it down until it stops. You control the bow "slam" by using your trim taps.
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I had over 1000 offshore hours on my single engine Gulfstream, and it was an absolute necessity to fully understand how all of the trim worked on the boat in order to run in the conditions we ran in.
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No matter what the boat, trim is a great thing and fully understanding how both motor trim and trim tabs work together on your boat will allow you to run your boat better. To get there, you have to do a lot of experimenting in many conditions.
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Start with your motors down and trim tabs up. As you come up on plane push the bow down with your tabs, then start to raise your engines. Your propeller will be at running maximum efficiency when you trim it up until you hear it cavatate, then trim it down until it stops. You control the bow "slam" by using your trim taps.
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I had over 1000 offshore hours on my single engine Gulfstream, and it was an absolute necessity to fully understand how all of the trim worked on the boat in order to run in the conditions we ran in.
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No matter what the boat, trim is a great thing and fully understanding how both motor trim and trim tabs work together on your boat will allow you to run your boat better. To get there, you have to do a lot of experimenting in many conditions.
wahoo33417
GreatGrady Captain
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I have been taught to use the trim tabs to get up on plane a bit easier and faster. From there, use the tabs as needed to get the bow up when its calm and down only to the extent needed when in a chop or to level the boat side-to-side. Then trim the engine to where your prop is level, i.e. not pushing up or down.
Idea is to use tabs to keep the bow down only to the extent needed, otherwise the engine is unnecessarily burdened, and keep the prop pointed in the direction you want to go - forward - for best efficiency.
Rob
Idea is to use tabs to keep the bow down only to the extent needed, otherwise the engine is unnecessarily burdened, and keep the prop pointed in the direction you want to go - forward - for best efficiency.
Rob
Wahoo and Kenlahr are correct..
On my 232 Gulfstream, I trim the engines up in calm conditions. They grab a little air, and I trim them back down slightly.
In a head or quartering sea, depending on the size and steepness, I trim the engines down. If it's still a rough ride, I start dropping the tabs 'till the bow cuts thru the chop smoothly. Adjust your speed according to existing conditions.
Do not use any tabs while heading downsea unless you need to level the boat.
I prefer not to use tabs unless needed, but they are an incredible tool to have. I would not own a boat of any size without them....
On my 232 Gulfstream, I trim the engines up in calm conditions. They grab a little air, and I trim them back down slightly.
In a head or quartering sea, depending on the size and steepness, I trim the engines down. If it's still a rough ride, I start dropping the tabs 'till the bow cuts thru the chop smoothly. Adjust your speed according to existing conditions.
Do not use any tabs while heading downsea unless you need to level the boat.
I prefer not to use tabs unless needed, but they are an incredible tool to have. I would not own a boat of any size without them....
tim is correct..every boat handles differently....run with the tabs all the way up and then tilt your engine a tad until you find that "sweet" spot...use your floscan, you will see the gph used go down but your rpms stay the same.
trim tab only to make minor adjustments...tap the controls to make those adjustments, dont press and hold like an elevator button!
good luck, all on the forum here to help.
trim tab only to make minor adjustments...tap the controls to make those adjustments, dont press and hold like an elevator button!
good luck, all on the forum here to help.
If you are not triming the motors up your are wasting a ton of fuel. On my Johnsons it is the difference between 32gph per cruise at 26knts and 24gph cruise at the same speed.
The best way to look at it is if your motor has any negative trim, meaning it is trimmed below perpendicular to the line of travel it is wasting thrust in turning the hull (bow up or down). You best bet is to the get the boat as level as possible with tabs fully up and get the motors just to cavitation and trim back down some. Then if you still need bow down add some tab deflection. Caution once you start putting tabs down you may need to go down on the motors a short burst since the tabs will create transom lift. After 5 boats I still find myself cheating and looking at the floscan as each different sea condition requires just a little differnet trim. But knowing how each works is key.
Your best fuel economy comes from a motor which is all thrust in the direction of travel and providing good hull ventilation. Tabs create lift, but also drag so minimize the tab. I like to have the bow just starting to rise and fall on a calm day. You want to maximize the air under your hull without going overboard or letting the hull slap. jh
The best way to look at it is if your motor has any negative trim, meaning it is trimmed below perpendicular to the line of travel it is wasting thrust in turning the hull (bow up or down). You best bet is to the get the boat as level as possible with tabs fully up and get the motors just to cavitation and trim back down some. Then if you still need bow down add some tab deflection. Caution once you start putting tabs down you may need to go down on the motors a short burst since the tabs will create transom lift. After 5 boats I still find myself cheating and looking at the floscan as each different sea condition requires just a little differnet trim. But knowing how each works is key.
Your best fuel economy comes from a motor which is all thrust in the direction of travel and providing good hull ventilation. Tabs create lift, but also drag so minimize the tab. I like to have the bow just starting to rise and fall on a calm day. You want to maximize the air under your hull without going overboard or letting the hull slap. jh
Use the engines to trim the boat first, then tabs if more trim is needed. Using only tabs adds resistance and when they are tabbed down. I only use my tabs to level the boat when it lists underway, or if I am running in a head sea I may use a little tab to put the bow down. To find the right spot for your engines to be tabbed, get on plane with them almost fully down, get a few rpm's below where you want to cruise at, then raise them up and watch the fuel management and fuel burn, it should drop, you should gain rpm's and speed all at the same time, after a while it will reverse and get worse, you want to be right before it gets worse. If seas are snotty you may not be able to trim as high, the props may cavitate, you will hear them if they do.
In conditions say you have heavy wind and wind waves coming at you off the starboard quarter bow, the boat will tend to heel into the wind as you maintain your line, and the waves will hit the side the hull and give you a beating. So you trim the boat to raise the starboard up so the waves come under the boat not hit the vertical side. Also trim the boat for imbalance in load, like when the LW is full the boat may tilt to that side, or extra passengers.
Use the boat tabs when it is too rough to plane, so you can lift the stern from making a hole and improve efficiency while doing so below normal planning minimum speeds.
Set engine trim for level to water irrespective of boat attitude and boat trim position, as a start.
As was stated, be very careful with following seas, boat and engine trim wise.
Use the boat tabs when it is too rough to plane, so you can lift the stern from making a hole and improve efficiency while doing so below normal planning minimum speeds.
Set engine trim for level to water irrespective of boat attitude and boat trim position, as a start.
As was stated, be very careful with following seas, boat and engine trim wise.
That is the best way I have ever heard it explained. I took a pararaph to try and say just that. jhBobP said:
JohnE, I read something like that in the Grady owners manual or one of the engine woners manuals. Easy to remember.
Trim boat first, then engine to follow. Even simpler to remember!
I also read at crusing speed and balanced loading assuming everything else is equal liek no water conditions, null out all boat trim, boat will align itself properly by design presuming level engine trim.
Trim boat first, then engine to follow. Even simpler to remember!
I also read at crusing speed and balanced loading assuming everything else is equal liek no water conditions, null out all boat trim, boat will align itself properly by design presuming level engine trim.
There is a good article on this subject in the June edition of Motorboating magazine. Just got my copy today. Check it out. I think it's on page 28.
capt chris said:
I was thinking the same thing....
I remember my old boat had quite a bit less power, and in a chop, it helped to push the bow down a little using the tabs as someone described above...... with the 265, in a chop, I just push the throttles down a little more and away I go..... to each his own I guess.....
Certainly worth mentioning, in a really rough sea, I have been able to get my planning speed (wave jumping speed) down by triming fully down on the tabs.... this will allow the boat to plane at slower speeds, but fuel economy for me is out the window in this condition......
Tim
fishingFINattic said:
I began to read your last line and before I finished I go wow when I do that my fuel efficiency is horrible, then I finished the sentence and saw you said the same thing, but there are times you need to do so. We needed to running the canyon last year, hit a 30mile stretch about 20-50miles out with nasty 6ft seas w/ 7's mixed in, put the bow down and ran 14-16mph on plane into them and never thought about going back, nobody onboard was taking a beating and the reports from the other side were flat calm and great fishing.... only problem was my .9mpg fuel burn with 800lb of ice and full fuel and gear with tabs down...ouch