Optimum Trim position

[2iar]

Still getting used to the new boat, and PT&T. I've got a guage for the T&T on a Signature 470DF and a 70 Four stroke Suzuki.

I've noticed that at approaching full speed in flat conditions, the boat is more comfortable with the engine trimmed in as far in as possible. When it's in the middle it maintains close to top speed, but porpoises a little.

Is it common to need the motor trimmed so far in when flat out, and what will this be doing to the fuel economy? Should the economy/performance be best in the centre position?

I've also noticed that I get on the plane quicker with the engine trimmed right in - is this common too?

Thanks,
Mike

[CQ_Fisher]

2iar, something not sounding right there. The part about jumping up onto plane quicker when trimmed right in is correct i always trim right in when starting off and them adjust to suit conditions once moving, i just find the boat likes it better that way. As for you comment about full speed in flat conditions, you should in flat conditions be able to trim right out to create less drag in the water by the hull, therefore creating fuel efficiency. I will say that my boat does not like to turn too sharply when motor is trimmed right out cause it cavitates really badly. If i see i have to turn for some reason i'll just trim back down slightly to make the turn and then trim back out once back in a straight line.

To sum up and answer yoru question. No, it is not common to need motor trimmed right in while travelling flat out. I would be going back to dealer and discussing this with them.

[sf17fisherman]

2iar, something not sounding right there. The part about jumping up onto plane quicker when trimmed right in is correct i always trim right in when starting off and them adjust to suit conditions once moving, i just find the boat likes it better that way. As for you comment about full speed in flat conditions, you should in flat conditions be able to trim right out to create less drag in the water by the hull, therefore creating fuel efficiency. I will say that my boat does not like to turn too sharply when motor is trimmed right out cause it cavitates really badly. If i see i have to turn for some reason i'll just trim back down slightly to make the turn and then trim back out once back in a straight line.

To sum up and answer yoru question. No, it is not common to need motor trimmed right in while travelling flat out. I would be going back to dealer and discussing this with them.

almost 100% right and it is sure right about how to start then trim out and not like alot of wallys do and try and start from a trimmed out posistion and wonder why the hole shot is bad
however diffrent boats like diffrent trim positions and while some can travle with trim out to the max other can not take much more than half however if you need to be in at full trim in then that also isn't right and would surget your motor hight is not corect or your prop isn't pitched right

[bidkev]

I'm similar to 2iar. If I trim out (past neutral) I get cavitation at sharp turns or following sea. I trim, right in to get out of the hole than put it neutral (half way) and use the trim tabs for trimming. I know this isn't the accepted proceedure here but I did quite a bit of research and many American sites advocate using tabs in this manner and not solely to level the boat. Hope I'm not doing anything wrong though as contrary to their personal beliefs, Americans do get it wrong sometimes

cheers

kev

[2iar]

Thanks CQ,

Yeah, it didn't seem right, that's why I asked. It's nothing too bad, but I thought I'd seek some opinions before it's due its' first service. I was thinking of fitting a foil anyway, but more to improve the holeshot. I'll see what they say, but I won't be putting it in for the service until after the new year.

Kingtin - Trim tabs aren't really an option on my size of boat, but I'd be interested to hear what you reckon this does to your fuel economy (it sounds more like you're compensating for the "problem" rather then correcting it). Of course, the Whittley chardonnay glitterati probably don't have the same concerns as us plebs

Thanks again,
Mike

[Argle]

Hi Mike, I have a 493F Signature and start with the engine trimmed right in for starting and once up on the plane slowly trim the engine out until its comfortable at the speed i want to travel. By playing with the trim you should notice the revs rising or dropping depending on the trim angle. In flat out mode just trim it out til it starts to porpise then trim it back down a touch and it should be just about right.
You should also notice the steering get a bit lighter as you trim it out.
As far as cavatation goes Im yet to get mine to do it, you can hook it hard into a turn with up to maybe a 1/3 trim and it will just pull straight around.
Fuel economy is better with less hull in the water- goes faster too

You might just need to play around with the new boat to get used to it, which is another good excuse to have it in the water

Cheers

[bidkev]

Thanks CQ,
<snip>
Kingtin - Trim tabs aren't really an option on my size of boat, but I'd be interested to hear what you reckon this does to your fuel economy (it sounds more like you're compensating for the "problem" rather then correcting it). Of course, the Whittley chardonnay glitterati probably don't have the same concerns as us plebs

Thanks again,
Mike

Wouldn't know about the fuel side of things Mike. It's in for it's first service so I should get a better picture after that. I meant to say that I only adopt the "trim tab method" when the sea's a bit lumpy. On a good sea she runs perfectly with tabs full out (nose up) and the engine trim at neutral. If I try to trim the engine past that, she starts to porpoise.

As for the Chardonnay.........I'm spent up now mate..........it's back to the Chateax de Cardboard Box.

kev

[banshee]

Basicly if there is more feed back through the stering turning one way as opposed to the other it needs triming in or out depending on what speed your doing,when the preasure is even both ways you should be in the sweet spot,if you can't get the sweet spot you will probably need to adjust the little fin under the cavitation plate.

[Sportfish_5]

Mike

As long as there is no engine height issues to sort out Argle is spot on and you should be able to determine the best trim position for cruising revs by just simply trimming the engine out (up) until the rpm and speed just increase. If you are driving the boat around with the engine fully trimmed in you may have a broaching problem when running downhill in largish chop. Less boat in the water faster the speed or less rpm needed for cruising speed. Just get the feel for it.

That Suzi will be nice and thrifty on the fuel

Kev - Show me a large boat with a big windage area and a sharp Vee that doesnt go better with trim tabs then I'll walk to China. The tabs are about getting the boat trimmed right, the power trim and tilt on the engine is about getting the prop to cut through the water in the most efficent position. The whole theory of bad designed boats needing tabs to cover the flaws is a crock of sh!t. Hey - they will make a bad boat ride better and a good boat better still.

Cheers

Greg

[2iar]

Thanks for the feedback guys, it's appreciated. The engine height, visually at least, appears ok, with the cav plate a little above the bottom of the hull. This is from memory though, the slope the boat's parked on in the back yard doesn't allow me to check it without taking it out...

Basicly if there is more feed back through the stering turning one way as opposed to the other it needs triming in or out depending on what speed your doing,when the preasure is even both ways you should be in the sweet spot,if you can't get the sweet spot you will probably need to adjust the little fin under the cavitation plate.

This is an interesting point. Fishin Dan noticed that my boat steered to the right a bit when he had a go. I put it down to him being [s]a big fat b******d[/s] bigger built than me

The fin isn't exactly in the centre (slightly to the right), but as close to it as possible as there isn't a more central slot for it. What is the fin for? This is all new to me, but I would have thought that it could only affect horizontal movement, not vertical? You might have hit on something here...

Thanks,
Mike

[banshee]

The fin is there to counteract the torque of the prop as it spins it shouldn't be straight,I'd be getting in cotact with the dealer and asking him to take you for another run in the boat,show him what your doing and take onboard his advice,could also be that the guage is incorrectly set,trim is very much a feel thing you will probably find as your experience grows with this boat you will discount the guage all together,mines been broken for three years and I don't miss it a bit.

[2iar]

Thanks Banshee,

Interesting point on counteracting the torque. You live and learn.

My gut feeling is that the guage is fine. When it's trimmed right in, it's reading correctly (ie the motor won't go any further down), and similarly, when it's right out, it's reading at the top.

Like I said earlier, it's not a huge issue so I'll hold off until the first service before raising it. I just thought from what you'd said earlier about the steering being affected you might have struck on something.

Thanks for the help,
Mike