Do I need trim tabs?

[Bifflefan]

I just bought a 16' 1974 starcraft with a 85 HP evin. and a 13.25x17 prop.
Havent had the chance to get it on the water yet, but the previous owner says that at speeds of 20+ it will get up out of the water and flop over on the starboard side of the bottom and ride there. making it want to turn to the right until you slow down. just wondering if anyone has an answer why and what to do about this.

 

[tashasdaddy]

Re: Do I need trim tabs?

soaked foam in the boat, unbalance load, motor trimmed wrong, does it have a whale tail on the motor now, get it off

 

[Boss Hawg]

Re: Do I need trim tabs?

soaked foam in the boat, unbalance load, motor trimmed wrong, does it have a whale tail on the motor now, get it off

Agree with all but whaletail-
I have basicaly the same - 16' 1987 starcraft with a 70 HP Johnson and a 13.25x17 prop, mine does great (level at slow speed, planes great, runs at over 30mph straight, level & true) with a small whaletale

 

[ezmobee]

Re: Do I need trim tabs?

I've got a 16' Starcraft with an 85 Johnson. Mine does close to 35 on a good day. It does sound like you have some kind of serious imbalance issue going on.

 

[Jdeagro]

Re: Do I need trim tabs?

Have you checked the steering trim tab? Are you trimming the motor out after you reach plane? Are you sure the boat is listing to starboard (right) or is it Port (left)?

Although tabs will fix the problem, It is best to identify the problem first.

 

[Bifflefan]

Re: Do I need trim tabs?

As i had stated i have not had it out yet myself. but after reading about motor height, i belive that the motoer may be to deep in the water. also i may be mistaken in the direction it leans as i havent had it out. the steering trim, if thats the little tab behind the prop, its pointing straight back. also the boat does not have a power trim, but i was told he ran it one hole from all the way down.
Next question: if its wet foam, how do i check, and can it be fixed?

you guys are very informative. ive been reading for 3 days and doubt ive gotten even 1/3 of the way around here.

 

[ezmobee]

Re: Do I need trim tabs?

Search "core sample" and you should find some methods of checking the foam. The gist is drill a hole in the floor and take out a sample of the foam and see if it's wet.

I think my motor is at that same trim hole so that's definitely a good starting point as is the trim tab being straight. You can make adjustments to those 2 things after you run it yourself and see how it performs.

As far as you motor being too low that's also a possibility but only a picture of your set up will help us determine that.

Is your boat aluminum or fiberglass? If aluminum replacing the wood and foam is no big deal. If fiberglass....much bigger deal.

 

[Capt'n Chris]

Re: Do I need trim tabs?

The only time you'll need trim tabs is if mother-in-law refuses to move to balance the load. Otherwise, you'll never need them.

Captain Chris

 

[NSBCraig]

Re: Do I need trim tabs?

The only time you'll need trim tabs is if mother-in-law refuses to move to balance the load. Otherwise, you'll never need them.

Captain Chris

 

[Bifflefan]

Re: Do I need trim tabs?

I got the boat out on the water this tuesday and it did just as i was told by the former owner said. it will lay over on the side that has more weight. now i know that for a small boat this is normal. but.... i had everything balanced out and did a slow, steady increase of speed, dont know how fast i was going as i have no speedo, but with no one moving i got the boat to the fastest speed of the day on a very flat calm spot, and as the speed increased around 30 if i had to guess. the boat all the sudden flopped over on the left side. had to back off the throttle fast at this point. the boat does plane nicely at a very slow speed tho.
1 more thing i could feel the water on the hull hitting under my foot at the fastest speed.
maybe its just not going to go faster than that.

also its a little envigerating when it does it at speed... LOL

 

[Splat]

Re: Do I need trim tabs?

Anybody else think this may be a torq issue?

If a weight problem I'd be expecting to hear of a list while the boat is at rest as well.

Does the boat sit level in the water when not underway?

Bill

 

[Bifflefan]

Re: Do I need trim tabs?

yes it sits level and the boat is not heavy. i had it weighed.
also under power it trys to to turn to the right from the motor touque i supose.

 

[BayBoy1750]

Re: Do I need trim tabs?

The hull may have a defect but it sure sounds like you are riding too high at speed which is likely caused by the whale tail. The whale tail gives an ever increasing lift with increased speed. You may be lifting the rear so much that suddenly the whale tail come out of the water causing a sudden change in attitude in the boat (flopping nose down) then your stuck there until you slow enough for the tail to resubmerge. Whale tails are good for getting out of the hole but the motor should be mounted high enough that the tail comes completely out of the water once on plane.

I don't recommend hanging over the back going 30 mph with a poorly performing boat to see whats happening. Just try removing the tail or adding lots of weight in the back (to try to force it to stay under) or raising the motor (to make it come out sooner).

My 2cents.

 

[Bifflefan]

Re: Do I need trim tabs?

I was told by the former owner that the tail made it better. i will try it with it off. I agree that hanging off the back is bad idea.
altho there is another post on this thread that the guy has a tail and his works fine. im also gonna try tabs and see if they help.

 

[BWR1953]

Re: Do I need trim tabs?

I was told by the former owner that the tail made it better. i will try it with it off. I agree that hanging off the back is bad idea.
altho there is another post on this thread that the guy has a tail and his works fine. im also gonna try tabs and see if they help.

Before randomly spending money on tabs or any other fix, I'd recommend finding out what the actual problem is first. Then move toward correction.

 

[Jdeagro]

Re: Do I need trim tabs?

I would agree with BWR1953, determine the cause then work on the solution. The hydrofoil will cause this at higher speeds simply because the stern is being lifted too much and the bow is too deep in the water, on a V bottom boat (especially). Since all of the extra stern lift is located in the center of the boat, it act like a teeter totter rocking to one side or the other very easily. If the motor trim is too far down then the prop will lift the stern too much. Check the trim.

 

[Capt'n Chris]

Re: Do I need trim tabs?

Is it the 16 Super Sport? I had one in 1973 with an 85 Evinrude. I put OMC Stinger carburetors, 65 flywheel and lower unit on it with one of the first teflon SST props and could hit 44 with 2 people and 2 full 6 gallon tanks. As for your problem, the boat needs nothing resembling tails and tabs. Those are generally used by the uninformed or rare and extenuating circumstances by the more seasoned skipper. Check your keel for perfect level with a straightedge and make sure it does not have a hook in it. A mal-adjusted trailer is a kiss of death. Then measure precisely from the tip of the bow around the gunwale to the tip of the corner bracket. Do this on both port and starboard. Then let me know.

Captain Chris
www.sternmate.com

 

[Bifflefan]

Re: Do I need trim tabs?

Check your keel for perfect level with a straightedge and make sure it does not have a hook in it. A mal-adjusted trailer is a kiss of death. Then measure precisely from the tip of the bow around the gunwale to the tip of the corner bracket. Do this on both port and starboard. Then let me know.

Captain Chris
www.sternmate.com[/QUOTE]

i measured from bow point to stern and got exactly the same number on both sides. now on to the second part. no.. the bottom is no where near flat or straight. i laid a 6' straight edge on it and could see the dips before it was even up against it.
Also got a good tip from a guy that builds (or used to) boats. he said that the strakes may need to be extended, bucause of the nonflatness of the bottom, as the water is getting confused as it come off them.
i may try this this winter if i have time.

one thing is for sure ill never buy a boat thats been on an easy loader trailer again.

 

[Capt'n Chris]

Re: Do I need trim tabs?

Is your keel hooked? Hooked would mean that the boat has been sitting on a trailer with at least one keel roller applying too much pressure in one place. Sitting for extremely long periods on a poorly adjusted roller will cause this. You will find it more in a wood or fiberglass hull hull than in aluminum, thus the reason for asking which Starcraft you have. Strakes are for tracking and banking and many boats have none. Starcraft has built boats since the big war and the are engineered very well...particularly the aluminum hulls. I would not attempt to change the hull design, but I have seen keels reworked once a hook has been found. Sometimes; however, it may not only be the keel that's hooked. The entire hull could take a set.

 

[Bifflefan]

Re: Do I need trim tabs?

I just put the edge on the keel and its good and straight. up to the rise anyway. there i have no way to check it.
It is fiberglass.
I think im going to try different holes in the trim before i get the tabs, with and without the tail. just to see for my self how it works. how knows i may hit on something that works.