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trim tab and prop question

S

schlosser1

Member
i just purchased a 88 ambassador today with a 454 and bravo 1 it has trim tabs that when all the way up they are parallel to the hull i noticed the bow does not come up as high as i think it should at full speed are the tabs suppose to go up in the back when fully closed? and also the boat has a 21 pitch cleaver prop which i believe should have more pitch what is a common starting point for this setup ? thanks.
 
Are you saying the trim tabs are even with the bottom of the boat when up. A 21p prop sounds a bit small for a 454 in a boat that size. I would try a 24p bravo 1. Try to borrow one and see how it does
 
yes, they are level with the bottom i would figure they are suppose to angle up when all the way up. the boat bow hardly raises at full speed im not used to trim tabs does the boat even need them? there is a 14 5/8 x 23p mirage prop for sale near me i was going to try that should be close right? thanks.
 
schlosser1 said:
yes, they are level with the bottom i would figure they are suppose to angle up when all the way up. the boat bow hardly raises at full speed im not used to trim tabs does the boat even need them? there is a 14 5/8 x 23p mirage prop for sale near me i was going to try that should be close right? thanks.
Click to expand...

Part of the no bow lift is a cleaver prop. Those are stern lifting props and are designed to run high, not deep like your situation. Put a mirage Plus on there, pitch, I am not sure, what is your gear ratio?
 
Its most likely a 1.5 on a 88 bravo unless somebody changed the gear ratio. The tabs should be angled up. A pic would be great.
 
I don't have any web accessible pics to post on here. If you give me your email address I can send one to you... Thanks for your help. I don't know how to post pics to this forum with out them being on the net...
 
that will be soon i am in the process of fixing the basket case a 100 things at once when i took it for the test ride the tach wasn't working i put a new one in as soon as i got it home next week i will take it out to see water
 
cool thanks i bought a 23p x 14 5/8 mirage prop yesterday for 150 and i am waiting for my new steering rack to get here so i can try it out. i am also going to zip tie up the trim tabs to see what happens
 
The tabs due look a bit low the the Cleaver prop is a stern lifting prop.
a mercury tempest 3 blade would also be a good try.
 
tried the mirage 23p yesterday after almost killing the motor from a bad impeller. it seemed to do pretty well at about 46-4700 rpm it has a couple dings but i think its worth fixing because its real close. i moved the trim tabs up to the top 2 holes and the boat moves along much faster at the top end. they stopped working anyway do you think my boat should even have them?
 
they are electric/hydraulic there are 4 screws that hold the top of the piston to the transom i moved the bottom 2 holes up to the top holes and just used the top two screws to temporarily hold the tabs up higher to see how it was.
 
Ok from the pic the tabs look low for being all the way up. I would adjust them up at a higher angle like you said. On your boat the tabs are good to use when trying to level the boat cruising to keep it from leaning. By this you lower 1 tab to straighten the boat. Another good use is when cruising around at mid to lower rpms you can lower them to push the bow down. Trim tabs are pretty much useless on wide open runs if you lower them it will slow the boat. 1 exception to this is at a wide open pass the boat tends to lean to the passenger side on a I/O with some horse power. dropping 1 tab a hair will straighten the boat giving you more speed. The only results you will see by this is a lot of seat time and a lot of speed runs with a GPS playing with the tab.
 
awesome thanks big red, thats what i wanted to know when i raised the tabs the bow came up nicely. before when the tabs were straight out when closed the bow did not hardly lift at all like a ski boat that seemed to suck up alot of speed and who wants that? thanks again, josh.
 
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