Bravo 1 increase negative trim cutting trim rods
 

I'm looking to increase negative trim on a Bravo XR. I've read about a couple of guys cutting 3/4" off the end of the rod and re-assembling. Anyone done this? I assume the bolt needs to be cut or replaced with a shorter one. I also think some non-essential part of the housing needs to be trimmed for clearance?

Ive thought of doing this also . I’d like to see what the feed back is on this topic. I know rams on the ITS system suck in further . They use a very short zinc in stead of the longer one.

https://cimg0.ibsrv.net/gimg/www.off...a3bb1f2138.png

I've read online about two guys that have done it. They said it helped with planing. I have a 26 Daytona -2 lower. They're fast, but very slow to plane with a "speed" prop. I'm not sure on the ITS, but the zinc length doesn't change the amount of trim "in", it's that the rods have bottomed out. The max trim out on the standard Bravo cylinder is 21 3/4". Too long to go lower. If you have a V hull apparently you need to be very careful about bow steer if you shorten the rods for negative trim. I think the Imcos have shorter trim cylinders. My buddy's Imco goes negative. I'm probably going to modify mine this week.

Member Tinkerer has a Daytona with a -3. Anyway, he modded his to get more negative trim. He mentioned how and how well it worked for him. Do a search or click on following and click thru his posts:
https://www.offshoreonly.com/forums/...archid=2792608

I know the zinc has no part of determining the stroke of the ram. But if you look at the picture you can see how far the ram goes in compared to a standard bravo.

That link doesn’t work. I’d like to read on what he did.

bummer it didn’t work. However,
You can get to same place. Click search above. Click on advanced. Go to search for users name and enter Tinkerer. Click search . You can scroll thru his posts to find them.

I found the thread but it doesn’t say what he actually did . It just says he cut a little here and grind a little there.

Bummer again.
Try a PM. He has good knowledge on many things. Hopefully he’s around and see’s the pm. I know he hasn’t posted here for 2 yrs or so ????

Yes, one of the articles I read was from Tinkerer. I also saw he hasn't been on here a couple of years and didn't think he would see a PM. @Cig28, yes I can see from your pic the ITS has a shorter zinc and looks like it pulls in more. The other guy said cut a maximum of 3/4" off the rod, cutting more does not result in more negative trim.

I’m going with cutting the rods and taking a small piece out and weld them back together. My winter project.

What are you planning to use to cut the rods? You're not going to take the rods out of the trim cylinder and cut the ends where the bolt attaches?

I’ll cut the rod with cut off wheel about an inch back from where the hinge pin is and take 1/2 to 3/4 out. Chamfer the edges, Reweld it but still be able to use the zinc. I’ll have to take the hinge pin out to see how much further in the drive tucks in.

You can only cut out that pice that the drive can swing down without the rams hang in. If you cut more out and you trim down you damage the Gimbel ring hing pins with your ram power.

You are correct I was looking at a boat at the marina I work at and the drive will only go in until the bell housing hits the gimble ring. So I have to make sure to cut the rams so that the bell housing does to touch the gimble ring.

Will it hit the gimbal ring if you only take 3/4" off the rods? Do you have a pic?

You should also allow a "little" extra room for the compression of the rubber mounts when with load in forward.

I think it will definitely hit the ring if I take 3/4’s off. I’m going to get the right measurement when I take the hinge pin out to see how much more negative there is to play with.

Well after going to remove the trim cylinders today, I realized the drive already hits the gimbal ring. It appears I have some negative trim. It looks like a lot of work to shorten the rods, trim metal on the drive and maybe off the gimbal ring just to get a little more negative trim. I'm thinking there may not be much benefit in the small amount of increased negative trim I might be able to get.

At least you were smart enough to look it over before you did a bunch of work for nothing.

I agree there is minimal gain to go thru all that work. I’ll live with the fact that I have to
bring it up to 3500 to get on plane.

LOL. Yes. It's on a lift so it makes it more difficult to check out. I had to borrow a friend's small floating dock to get to it.

That's my rpms too. Lots of bow rise still and fairly slow to plane out. I already put on a Max Machine Worx cavitation plate and run a 5 blade. Next I'll have to look into a 1" driver spacer.

Do you have trim tabs? You can drop a little tab to get you on plane then pull them back up...that way you don't lose anything on the top end with spacers and what not...I believe in this situation the five blade may be hurting you...might be biting too hard initially causing the bow to rise and then doesn't have enough to make it fall over....could be way off but a possible lab job on the prop from a reputable source may solve your issue...just some thoughts before you start going down a rabbit hole of endless parts and time.

Stewart

I think my problem is my x dimension is high. The shafts are 3” below the bottom. I’ve tried my tabs in all location and the only way that helps a little is all the way down. I have 280 tabs and was thinking the longer 380 tabs my help. If I find a set of 380 plates I’ll buy them and give it a shot.

Was just a suggestion...that's weird about your 280's..I put 280's on mine when I did my refit and if I bump those things at all down you can feel it! Granted I only have a 28 nordic heat but they make a world of difference for me. I believe hardin marine sells a kit to upgrade 280's to 380's I think. May be worth a look

Stewart

I have a 30 Cig Mystique Twin Step

Where are you tabs located on the boat? Mine are as wide as I could get them on the back and the hinge pin is about an inch above the bottom of the boat. Yours isn't that much bigger than mine and its crazy to me seeing what mine do that your 280's don't bury the nose of that thing when down. If I drop mine like an inch below the bottom it physically lifts the back of the boat and buries the nose. Your boat is heavier with a deeper vee and twins in the back so I'm sure all of that comes into play however. Plus you're stepped and mines not so that plays in a little too.

Stewart

A simple mod for negative trim is running the "celery stick" in the rearward position.

https://cimg5.ibsrv.net/gimg/www.off...ffd97b0c5.jpeg

My dog bones are in the correct location (top photo).

https://cimg1.ibsrv.net/gimg/www.off...6499a3719.jpeg