Freedom 235 proper trim

[thePearlyWhite]

I have a 2023 Freedom 235 and I am having a hard time determining where exactly proper trim level should be when cruising or even attempting to hit top end. I grew up driving speed boats and I could always feel the hull come out of the water and start to want to dance more. The Grady doesn't seem like that type of hull design or boat for that matter. But I still am having a hard time getting a feel for it. I also seem to have a hard time hearing when cavitation is starting or even feeling it for that matter. Where do 235 owners like their trim at when cruising pushing top end? I'd like to have ideal hull out of water to help with full efficiency. Trimmed up 25% 40%?

 

[seasick]

To get an idea of a decent starting point, get on plane in relatively calm seas, with the trim tabs fully retracted and the motor trimmed all the way in ( down).
Run at a decent cruising motor speed and after waiting 20 seconds or so for things to stabilize, note your speed on the MFD). Now trim the motor out (up) a little at a time and watch your speed. It should increase after a short delay and will top out at a point after which it should start to decrease. Trim the motor in a bit until you max out the speed. That angle is in the sweet spot.

Many folks state that you should not use the trim tabs except to correct for list but rather should focus on adjusting motor trim. I generally agree but many have stated that they get better performance with some trim tab application. You have to experiment to see what works for your situation.
Note that the optimal motor trim angle will change as your speed changes and as sea conditions and boat load ( and distribution) changes.

Prop ventilation ( probably what you are calling cavitation) should be avoided in general . Often you can hear the difference in the sound of the prop as bite is lost.

 

[FREEDOM!!!]

I keep my 235 trimmed at about 50-60% on plane. Almost never have to use the tabs. It's such a heavy boat for its size that it just naturally cuts through the waves without much need to fuss a lot with trim tabs. But I can definitely hear cavitation if I trim up too much.

 

[seasick]

I keep my 235 trimmed at about 50-60% on plane. Almost never have to use the tabs. It's such a heavy boat for its size that it just naturally cuts through the waves without much need to fuss a lot with trim. But I can definitely hear cavitation if I trim up too much.

What does "trimmed at about 50-60%" mean?

 

[FREEDOM!!!]

What does "trimmed at about 50-60%" mean?

Engine trimmed up around 50-60% like this.

 

[FREEDOM!!!]

At top speed its usually a little bit more, like around 70-80%.

 

[seasick]

Trim is measured in degrees usually and can be negative. On your boat and most similar pleasure craft, when the motor is trimmed all the way in (down) it is at a negative angle. I am not sure what the bars represent on your display, typically they would display all the way in with zero or one bar and out of the water storage position when bars are all displayed.

 

[DennisG01]

Pearl, you should have at least a basic fuel management gauge, right? Pay attention to that on a relatively calm day and that will help you dial things in... at least for those conditions. But the answer to your question is really just "it depends". There's way too many variables to focus on one particular setting. Now, how do you figure this out? That answer is simple, as well... "go boating more"!

 

[luckydude]

Wow some very different advice from what I do. I think Seasick gave good advice, trim it all the forward, get on plane, watch your mpg, start trimming it back and the mpg will go up (a little, for me it is .1 mpg so it is subtle). Keep going as long as the mpg goes up, as soon as it goes down, you have gone too far.

For the first couple of years, I ran my 228 with the engine trimmed all the way forward, that's what the Grady tech guy said to do. Reason is that the cavitation plate acts as a trim tab, when the engine is forward it will lift the stern, push the bow down, the boat cuts through waves better.

I would NEVER run my boat with the engine trimmed back 50-70%, that will lift _my_ bow like crazy which means I am smacking into the face of each swell and I'm launching off the top of each swell. Maybe you Florida people can do that, but that is the path to a back that won't work for a week if you are on our Pacific.

These days, because my buddy Jens made me upgrade my trim tabs to the proper size (according him and Bennett), I do trim my engine back about one additional bar on the display, that's my MPG sweet spot. Then I use the tabs to push the bow down.

Whatever you do with all us internet people, just think. The engine trim affects your ride, trim it forward, the bow goes down, trim it back, the bow goes up. If you get the cavitation plate parallel with the ocean surface, that's the least drag, the most MPG. In most cases that is what you want. If you don't have trim tabs and you are in slop, you want that engine trimmed forward so you push the bow to cut through the waves. If you have trim tabs, learn from as I have learned from people here, use them. And be aware that on many Gradys the tabs are way too small. Bennett says for 9 inch deep tabs, you want an inch in width for each foot of hull. Grady gave me 9x12 tabs for a 22 foot boat. Ouch. I went to 12x18 and it is night and day better.

 

[DennisG01]

Lucky, just a little clarification on your post for "educational" sake

The cavitation plate you're referring to is correctly referred to as an anti-ventilation plate. Cavitation is an entirely different thing. The plates primary purpose is to help prevent air from being sucked down into the prop.

The plate, however, is not the major means of force direction. While it does help a bit, the primary means is from the thrust of the propeller. Every action has an equal and opposite reaction... so when the motor is tucked all the way in, the prop thrust is directed downward and the opposite reaction is to lift the stern... and the opposite reaction of that is to lower the bow. I'm probably telling you something you already know, but that's the jist of it.

 

[FREEDOM!!!]

Trim is measured in degrees usually and can be negative. On your boat and most similar pleasure craft, when the motor is trimmed all the way in (down) it is at a negative angle. I am not sure what the bars represent on your display, typically they would display all the way in with zero or one bar and out of the water storage position when bars are all displayed.

The OP has a new 235. He has the Yamaha display that I posted. The yellow indicator shows the trim position of the engine. No yellow blips means the engine is all the way down. More yellow blips means the engine is trimmed upward. I always start with the engine trimmed all the way down. Once on plane I start trimming the engine upward till I hear it start to sound weird then I back it down a notch or two. A lot of people always keep the engine trimmed all the way down then use the trim tabs to adjust the bow. That works, but the trim tabs add drag. It's not very efficient. I use them as little as possible.

Also, once you get to a comfortable speed, adjusting your engine trim will change your RPMs. Let's say you are on plane and running 30mph at 3800rpms. Without touching the throttle, if you start adjusting the engine up you will see the RPMs increase and your speed increase. Your fuel efficiency will also increase. The 235 is a heavy boat for it's size. You don't need much trim tab at all. My previous boat was a 21' Seafox that was much, much lighter. I had to use a lot of trim tab to keep the bow down, and even then it would get hammered in even light chop. This Grady handles the chop with ease even with no trim tabs. I really only use tabs to correct list.

 

[FREEDOM!!!]

Wow some very different advice from what I do. I think Seasick gave good advice, trim it all the forward, get on plane, watch your mpg, start trimming it back and the mpg will go up (a little, for me it is .1 mpg so it is subtle). Keep going as long as the mpg goes up, as soon as it goes down, you have gone too far.

For the first couple of years, I ran my 228 with the engine trimmed all the way forward, that's what the Grady tech guy said to do. Reason is that the cavitation plate acts as a trim tab, when the engine is forward it will lift the stern, push the bow down, the boat cuts through waves better.

I would NEVER run my boat with the engine trimmed back 50-70%, that will lift _my_ bow like crazy which means I am smacking into the face of each swell and I'm launching off the top of each swell. Maybe you Florida people can do that, but that is the path to a back that won't work for a week if you are on our Pacific.

These days, because my buddy Jens made me upgrade my trim tabs to the proper size (according him and Bennett), I do trim my engine back about one additional bar on the display, that's my MPG sweet spot. Then I use the tabs to push the bow down.

Whatever you do with all us internet people, just think. The engine trim affects your ride, trim it forward, the bow goes down, trim it back, the bow goes up. If you get the cavitation plate parallel with the ocean surface, that's the least drag, the most MPG. In most cases that is what you want. If you don't have trim tabs and you are in slop, you want that engine trimmed forward so you push the bow to cut through the waves. If you have trim tabs, learn from as I have learned from people here, use them. And be aware that on many Gradys the tabs are way too small. Bennett says for 9 inch deep tabs, you want an inch in width for each foot of hull. Grady gave me 9x12 tabs for a 22 foot boat. Ouch. I went to 12x18 and it is night and day better.

I think there is some terminology confusion. Forward, back, up, down.... When you say forward, you mean down and back means up, correct?

 

[seasick]

I am not so sure I agree with the statement about watching the revs. In theory, the revs when in cruising range should remain steady. That is a function of the motor's engine computer. The speed will change though as the drag changes.
The optimal angle of motor trim is not a constant and depends on a lot of factors but all else equal, the sea conditions can dictate the best setting. For example you may need to increase the trim to keep the bow from stuffing itself into swells or to reduce bow steer. On the other extreme, the 'normal' trim for cruising may need to be lessened to reduce purposing .
As is often the case, experimenting and trying different settings is the way to go. Just remember to make small changes and give the vessel time to reach its equilibrium

 

[FREEDOM!!!]

I am not so sure I agree with the statement about watching the revs. In theory, the revs when in cruising range should remain steady. That is a function of the motor's engine computer. The speed will change though as the drag changes.
The optimal angle of motor trim is not a constant and depends on a lot of factors but all else equal, the sea conditions can dictate the best setting. For example you may need to increase the trim to keep the bow from stuffing itself into swells or to reduce bow steer. On the other extreme, the 'normal' trim for cruising may need to be lessened to reduce purposing .
As is often the case, experimenting and trying different settings is the way to go. Just remember to make small changes and give the vessel time to reach its equilibrium

Next time you are cruising at a constant speed, try adjusting the engine up and down. The RPMs should go up or down a few hundred depending on the angle of the engine.

 

[seasick]

Maybe it is engine dependent but I am pretty sure that Mercs will not change revs. When I get back on that bot and have a chance I will test out the theory.

You don't have auto-pilot on when changing the trim di you?

 

[Peter A]

General guidelines to follow for sure, but also very boat model and individual boat specific depending on configuration. I am learning that on my 208 I use more engine trimmed in that I originally anticipated. My theory is that with the short boat, the transition to the shallower deadrise happens pretty fast so keeping the sharp end of the boat down is important in all but a truly following sea. She is heavy for size with a hardtop but still short, with the engine on the transom not on a bracket like a 228.

 

[seasick]

General guidelines to follow for sure, but also very boat model and individual boat specific depending on configuration. I am learning that on my 208 I use more engine trimmed in that I originally anticipated. My theory is that with the short boat, the transition to the shallower deadrise happens pretty fast so keeping the sharp end of the boat down is important in all but a truly following sea. She is heavy for size with a hardtop but still short, with the engine on the transom not on a bracket like a 228.

On my 208, no hardtop, I find it runs better with a few degrees of trim up. I find the hull very prone to bow steering. Motor is a 150 OX 66.

 

[FREEDOM!!!]

General guidelines to follow for sure, but also very boat model and individual boat specific depending on configuration. I am learning that on my 208 I use more engine trimmed in that I originally anticipated. My theory is that with the short boat, the transition to the shallower deadrise happens pretty fast so keeping the sharp end of the boat down is important in all but a truly following sea. She is heavy for size with a hardtop but still short, with the engine on the transom not on a bracket like a 228.

Yes, boat model and size matter greatly. Hull design, length, width, weight, all will change trim requirements. Grady's are pretty heavy boats, which contributes to their famous comfortable ride. The only time I use trim tabs is when getting out of the hole. Put the tabs and the engine all the way down, hit the throttle and the whole boat almost instantly lifts out of the water without any bow rise. Once on plane (which only takes a couple of seconds) I immediately retract the tabs fully and start trimming the engine up, usually to about 50-60% (5 or 6 yellow blips on the engine monitor). Almost never need to use the tabs while cruising. My old boat was much different. Trim tabs were in constant use.

 

[Peter A]

On my 208, no hardtop, I find it runs better with a few degrees of trim up. I find the hull very prone to bow steering. Motor is a 150 OX 66

To the OP, good luck getting good trim setting for you 235, extrapolating experience from other hills.

On the 208 with Yamaha 200 running a 4-blade Solus 14.5x15, trimmed in to start, then typical running for me is 3 bars up the digital gauge. Really rough taking it on the bow I will trim all the way in, even add a little bit of tab (2-3 lights on the Bennet indicator). Yes, some bow steer on an odd wave.

The Solus 4-blade was installed by prior owner and he did not keep the OEM 14.25x17 3-blade Reliance. Too bad for me.

 

[luckydude]

I think there is some terminology confusion. Forward, back, up, down.... When you say forward, you mean down and back means up, correct?

Down and foward are the same thing, up and back are the same thing. Down/up are a little confusing because your engine starts up high before you put it water and put the engine down. But you go in the down direction enough and most, if not all, outboards will go past the 90 degree straight up and down and tilt the plate forward a bit. So it acts like a trim tab.