How far up do tabs go????

[crazy charlie]

I have had a problem with my 280 Regal not being able to get my bow up after planing off.I cavitate almost immediately.I already bought new 4 blade props to hopefully solve this.I was wondering if anyone knows how far up trimtabs should go when fully retracted????Mine look like they go about even with the bottom of the stern.I cant remember but I think my last boat retracted to a pretty good angle when pulled up full.I was wondering if the trimtab piston is mounted too far down thus not allowing the tab to go far enough up and this could be why I cant get the bow up???? Charlie

 

[imported_Mike_M2]

Re: How far up do tabs go????

Even is about normal. Are you sure your outdrive is trimming down enough?

 

[Dhadley]

Re: How far up do tabs go????

I would say youre right, theyre mounted too low and/or are mounted so they cannot retract far enough. <br /><br />Take them off and give it a try. That will answer your question right away. We do it all the time.<br /><br />What 4 blade props did you try?

 

[crazy charlie]

Re: How far up do tabs go????

Yes,I have twin alphas and they go down fully.Charlie

 

[LubeDude]

Re: How far up do tabs go????

"was wondering if the trimtab piston is mounted too far down thus not allowing the tab to go far enough up and this could be why I cant get the bow up???? Charlie"<br /><br />"Are you sure your outdrive is trimming down enough?"<br /><br />Im confussed! <br /><br />You are trying to get your bow "UP"???<br /><br />Trim tabs generally are used to get your bow "DOWN" or to even out your plane.<br /><br />Trimming fully down will push your bow down. What is it you are trying to achive exactly???

 

[imported_Mike_M2]

Re: How far up do tabs go????

Yea, unusual, as the big complaint is the opposite. Charlie, does the bow drop that much? Obviously, the bow is way up before you plane, then you say it drops that much to cavitate?

 

[ThomWV]

Re: How far up do tabs go????

The standard for mounting trim tabs is to have the trailing edge of the tab 1/2" above the hull bottom. The way this is done is straight forward.<br /><br />When installing them what you do is screw the tabs mounts to the transom with them hanging. Then you take a plank (I use a chunk of 2x6 about 4 feet long) and put it flat under the boat so that it sticks out the back and the tab plate rests on it. Then I take a jack and use it to hold the plank up against the hull. With that in place the tab itself is exactly even with the hull bottom. Then I take a half inch square length of wood ($0.49 at Lowe's) and use it to hold up the aft edge of the tab away from the plank. That holds everything in place so that the piston can then be pushed back against the transom and the three holes drilled to mount it in place. All of this takes roughly 5 minutes per side to do. Once the three holes have been drilled (I am assuming you are using Bennett tabs) then remove the piston and drill the hole for the nipple for the hydraulic lines. By the way, if your transom is too thick for the nipples that come with the tabs just head to the local hard ware store for a pair of longer ones - they will run you about a buck apiece.<br /><br />For whatever its worth tabs mounted this way, or even if they were mounted without putting the space in there to hold them up, would still not have any effect on the boat when it was up on plane if the tabs were fully retracted. I don't know why so many people miss this simple fact - trim tabs have no ability what so ever to lift the bow of a boat, all they can do is force it down.<br /><br />Only two thing will lift the bow of a boat; the shape of the hull and leading edge rake of the prop. The 4-blade you mention will allow you to run the engine higher without it airating (sucking air from above the prop) and most of them have fairly high levels of trailing edge rake which has the effect of lifting the stern, but its not at all likely that its going to lift your bow. Just thought you should know before you put out a lot of money for one.<br /><br />Thom

 

[crazy charlie]

Re: How far up do tabs go????

I bought 4 blade quicksilver props which i have not tried yet.The o/ds trim up and down perfectly.The bow rises as usual when planing and once planed off rides level which is fine if there is no chop which is almost never.When trimming the drives up after planed to raise the bow the props begin to cavitate before I can get the bow high enough.I understand that trim tabs are for pushing the bow down and some side to side but in my case I think they are not allowing my bow to rise.The tabs seem to mounted where they would usually be but the pistons may be a little too low which would not allow to retract as far as I may need it to.Charlie

 

[Dhadley]

Re: How far up do tabs go????

Thats more common than folks think. Thats why we just remove them and give it a quick try.

 

[crazy charlie]

Re: How far up do tabs go????

Do you mean remove them all together???It may be easier for me to move the pistons up some.Charlie

 

[imported_Mike_M2]

Re: How far up do tabs go????

It might be easier to move the pistons out further on the tab to get the same affect, just drill new holes. Gotta be better than putting more holes in the transom, but do like suggested and unbolt the piston from the tab and tie them up for a test drive first.

 

[crazy charlie]

Re: How far up do tabs go????

Yea I agree,I hate drilling any holes in my boat let alone below the water line.Charlie

 

[LubeDude]

Re: How far up do tabs go????

I understand now. Your new props are going to help some, but your boat may just be too heavy in the bow. Can you move any weight from the front to the back?

 

[crazy charlie]

Re: How far up do tabs go????

LD not a chance of that. 2v8s 2o/ds and 2 gastanks and a fiberglass swimplatform ,all in the back.Nothing in the stern to lighten up.Charlie

 

[Dhadley]

Re: How far up do tabs go????

We dont redrill any holes until after weve tested. Disconnect the cylinder from the tab, secure the tab completely up and out of the way and try it. <br /><br />If it helps then we reposition the cylinder higher to get more of the tab up.

 

[crazy charlie]

Re: How far up do tabs go????

Dhadly,how much of an angle would you estimate the tab should be if in the full up position in relation to the bottom of the stern??I dont have the luxury of being able to haul the boat after it has been launched so I may move the piston up a little or as suggested before move the piston on the tab.Charlie

 

[Bondo]

Re: How far up do tabs go????

charlie,<br />ThomWV explains it Very Clearly.....<br />The tabs should be Barely above Level.....<br />So they act as an Extention of the hull.......<br />I Really Doubt the tabs are your Problem.....<br />Sounds to me, that you need to Unload all the Extra Junk out of the front of the boat....... <br />I also agree with ThomWV, That 4blade props are Probably Not going to Help you 1 Bit.....

 

[Jdeagro]

Re: How far up do tabs go????

Crazy Charlie<br /><br />Like DHadley said (especially if your in the water) disconect the actuator from the trim plate, move it out of the way and pull the plates up. Take the boat out for a test ride. You will know immediately if the plates are too low and lifting the stern when cruising. If you find that this is the problem then if possible, relocate the actuator on the plate (further to the back (trailing edge) or move the transom end higher.<br /><br />I am not a prop man so I may be wrong, but the four bladed prop may give you more lift at the stern. <br /><br />Do you have any other planing devices on the boat or motor, and how large are the trim plates?

 

[crazy charlie]

Re: How far up do tabs go????

Nothing in the bow to lighten up except a bottle of chardonay or 2.The tabs are pretty large though I dont know the measurements off hand.I think I will try to move the piston up a little,it surely couldnt hurt.Hopefully the 4 blade props will help too.I may even drill the holes in the drives for doel fins so I can add them once in the water to see if it helps at all.Charlie

 

[ThomWV]

Re: How far up do tabs go????

Look,<br /><br />There seems to be a lot of confusion here. You can not simply move the cylinders up a little bit and you can not simply move the mounting point back a little bit.<br /><br />The piston bolts directly to the very back edge of the trim tab, on a section that is bent up. There is no place else to mount them, so moving the mounting position back simply is not going to happen.<br /><br />On the top end of the piston its held in place by three large screws (usually #12 or #14) and right dead in the middle of all of that there is a 3/4" hole going right through your transom. Moving the tabs up means that you have to remove it from its mount. That means removing the hydraulic line, and then filling all 4 holes, and then remounting. You aren't going to be able to do any of this with the boat in the water - no way on earth.<br /><br />Also, under no circumstances should you disconnect that piston from the tab plate and then take the boat for a spin. If you do you'll be dam good and lucy to have a tab when you get back or to find that you have a transom that isn't beat all to hell and gone.<br /><br />If the boat is in the water and you're in a place where its even a little bit warm just take a straight edge (aluminum yardstick will work just fine) and jump in. Have the tabs in the full up position and press your straight edge up against the bottom of the hull so that it extends out under the tab plate. If the straight edge is agains the hull you'll see if the tab properly mounted or not in a heartbeat. If its not this is going to require a days worth of work with the boat on land. There is simply no choice about that. Screwing around with anything else is just wasting your time.<br /><br />Thom