trim tab help

[66mstgfsbk]

i have a malibu 21ft open bow low profile ski boat with a 305 omc stringer. the question that i have is my boat only planes when im above 30mph then i can back the throttle down and cruise at 25 any lower and it will not plane. is the smart tab set up good for what i need or should i go with another brand. i need it to plane because i take on water since the rear gets real close to the water, but once the front goes down it gets better and the water only sprinkles in not splashes in quarts. thanks for any help.

 

[Mischief Managed]

Re: trim tab help

I think you may have other issues causing the planing problem. How's you WOT RPM? Is it within the recommended range? If not, you could have weight porblems (does the boat have trapped water in the hull?), power problems or prop problems (wrong pitch, dinged up, ventilating etc.). It would be wiser to fix those things before adding tabs.

 

[jaxnjil]

Re: trim tab help

I think you may have other issues causing the planing problem. How's you WOT RPM? Is it within the recommended range? If not, you could have weight porblems (does the boat have trapped water in the hull?), power problems or prop problems (wrong pitch, dinged up, ventilating etc.). It would be wiser to fix those things before adding tabs.

true true; need to check your speed with a hand held gps

you should be trying to plane at 15 to 22 mph and on plane by 25

 

[66mstgfsbk]

Re: trim tab help

now that i think about it i think your right it starts planing about 22 or so but any less and the bow stays up real high. i have not taken the boat all the way to wot because the most ive taken it to was 4500rpm and we were doing 55. if i go that fast or faster the speedo pickup folds and i lose speed reading. im in the process of finding my gps so i can get a better reading. the prop is alum and has a few little dings but nothing really bad in my opinion at about 55 the prop sounds like its gurgling, is that cavitation? it is a omc stringer so there is no trim adjustment. i believe there is no water trapped, i just redid the deck, transom, stringers, and seals. i just wanted to see if there is a solution for making it plane quicker so i can put the kids on a tube and go slow. i tried putting weight in front it helped a little not much, it seems like if i do a hole shot and it planes down i can slow down but too slow and up the bow goes again. thanks again for the help

 

[jaxnjil]

Re: trim tab help

a 4 blade prop would get you up quicker and the solo props sold here worked well for me when i was chasing wot --verse prop pitch.

i think i got a couple on sale last summer for $118 each and shipping included but that was on sale

 

[66mstgfsbk]

Re: trim tab help

im happy with the boat doing 50-55 im just trying to get it to plane quicker. i have no idea what the current prop is so i have no idea where to start. i have another prop i think is a 14x19p. should i try a 4 blade or would trim tabs help me out in this situation?

 

[jaxnjil]

Re: trim tab help

both would help. which one to try first is a tough one.

my personal opinion; at 21 ft and a ski-boat i would go for the 4 blade prop to get a hole shot under load. i like the bite out of the hole you get with a 4 blade
especially if you dont mind giving up a little top end speed


need to make sure engine is tuned and running good before you spend any money on other stuff though

 

[66mstgfsbk]

Re: trim tab help

im not worried about top speed im just trying to get it to plane a little quicker so i can pull the wife and kids on a tube. if i can bring the bow down just a little while going slow ill be happy. if i go the trim tabs way is the smart tabs good enough or do i have to get adjustable tabs? i have a 14x19 stainless that a buddy just gave me, would that help any in finding a answer? the engine runs good the tune up was just done and now im on the hunt for a pertronix. thanks for all the help

 

[jaxnjil]

Re: trim tab help

my opinion again but i would go with adjustable tabs on a 21 ft. boat

not knowing what props and wot you have now its tough to say about props.just because its a stainless prop doesn't mean its a performance prop.
i had a quick sliver SS prop that's a 3 blade and it runs pretty much like the aluminum 3 blade i have. i have two mirage twos that are 15 "dia and more of performance prop for a B I and they have more cup and run smother than any other props i have.

i found i could get close to the same performance from the smaller diameter 4 blade aluminum props with out the expense of SS.

i would really work on making sure your boat is propped right before you spend the money for tabs.
at best with tabs; if your not properly propped you might get a little help from tabs but your just covering up another problem that sooner or later you'll have to work out. might as well make it sooner.
all so i think you can prop cheaper than adjustable tabs and propping will be a lot easier than adding adjustable tabs.
in other words proper order is to prop first then tabs if still needed

 

[66mstgfsbk]

Re: trim tab help

thanks for al the help jaxnjil

ill look into a prop but not knowing what i have where would i start? i can measure the current one but i have no idea what pitch it is. on one of the props it says michigan, the other is unknown, and the one i just got is a ss 14x19p. they are all 3 blade.

 

[jaxnjil]

Re: trim tab help

the prop pitch and diameter should be stamped on the hub. you might have to remove the prop nut to find it. if the prop has been reworked or re pitched it will most likely be stamped on the out side of the hub

you can find out what you have now and then you need to take the boat out and see what your wide open throttle motor rpm's are

i can't help you with the wot speck for your motor, but if you start a new thread in omc mercruiser inboard section some one with a omc might know

after you verified your wot rpm and your current prop pitch you will have the information you need to figure out what you need for a new prop.

you could try your 14x19 SS prop and check it also as you have it any way
the important figure with any prop you try is your wot rpm's and getting that into the proper rpm range for your engine

once you get there, if you still need more snap to get on plane you can look to the 4 blades ect.

hope this breaks it down enough to get you started

 

[slasmith1]

Re: trim tab help

Trim tabs would fix your issue. I would also suggest an inexpensive gps because I have never seen a pitot style speedo that was accurate.