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#12778657 - 06/03/18 12:35 PM Trim Tabs, Smart Tabs, Hydrofoil, Prop Questions.
psycho0819 Offline
Extreme Angler

Registered: 03/27/05
Posts: 1562
Loc: Kaufman
I know this is a little off topic for this forum, but I can't get good answers/opinions on the Club Sea Ray forum, so I come back home where I know opinions abound. smile

1978 SeaRay SRV 200 Sunrunner (Cuddy Cabin). 19'11" long, 8' wide. 5.0 Mercruiser with pre-alpha drive. The hull has a prominent keel all the way back to the stern, tall sides, essentially I consider it a little big boat, or a big little boat.

I bought this boat as a project, and boy has it been one. I've fixed and replaced a whole host of hacks and worn out stuff. Had the engine out replacing motor mounts, and a lot of stuff discovered during that process. When I had the drive off, I removed and tossed the old stingray style hydrofoil that was on it.

Last year, before all this was done, with the foil still on the drive, the boat handled pretty good, planed pretty quickly, and it kept the bow down as one would expect, but I had a hard time trimming to get the bow up very much at all. Definitely couldn't get the bow up where I wanted it, or thought I did anyway.

The prop is a cleaver design, trailing edge is straight from the pointed tip back to the hub. The only numbers I can find on it are "15-M". It is a 15" diameter prop, so I don't know if the number on the prop indicates that, or 15 pitch? With the 305 throttled up to about 4,300 rpm (likely about the max rpm for the stock valve train), the boat would run around 40mph.

Now, with the foil removed, it takes for ever to plane, bow rises dramatically, and I can't get it to settle down. Trimming up any at all results in porpoising. Not how I want this boat to handle.

So I'm faced with a few options here.

1) Put the foil back on and call it a day.
2) Install trim tabs.
3) Install a set of smart tabs.


1) I understand the foil puts a good amount of additional drag on the drive, which might not be the best solution. I also go back to not being able to get the bow up when on plane.
2) I'm not excited about the price of full on trim tabs, although I know they'll be the best option. Also not excited about having even more moving parts on the boat to eventually fail, because don't they all, eventually?
3) The smart tabs seem to address my issue and my budget, better, but I'm just not sure if I'm reading a bunch of marketing hype, or if they'll give me the results I seek. I know some tuning will be necessary with smart tabs, and I do have more time than budget should this be the case.

So there's my dilemma, and my known options. What say the TFF guru's?

I know the easy answer for everyone will be, spend the money for trim tabs. What I'd like to see is some pro's and con's to the other options along with that statement. I've never ran a boat with trim tabs, and although I've read quite a bit on the subject while researching, I'm just not sure the expense justifies the results I'm seeking.


I do plan on playing around with some props as well. From the little bit I can glean on the prop I have it's not the best style for my application. But having been an OB guy for, well, for ever, I have no clue where to even start on a rig like this. Any insight here?

The desired use for the boat is to be a typical run about, some water sports, maybe even some fishing on days when the lake is too rough for my 18' mod-v Xpress. Once I get things all shaken out, a trip to the coast to fish some close rigs in good weather is not out of the question. In other words, just an all around use boat that handles good.

Thanks.
_________________________
If you're not living on the edge, you're taking up too much space!

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#12779126 - 06/03/18 10:09 PM Re: Trim Tabs, Smart Tabs, Hydrofoil, Prop Questions. [Re: psycho0819]
Pat Goff Online   content
TFF Celebrity

Registered: 01/29/05
Posts: 5850
Loc: Marble Falls/Seadrift
I’m not a fan of foils. At best they are a band aid for bad setup.

I do like trim tabs. Much more useful
Your prop is 90% of your boats performance until it’s right nothing else is right.

I like the four blade offshore unvented design for your hull and motor. Should deliver a nose bleed holeshot and maintain good water contact and handling in any condition or trim angle.
I’d thing you want more rpms but you need to research that number.
Call powertech props and have them fix you up.
_________________________
Pat Goff
Marble Falls/Seadrift TX



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#12779598 - 06/04/18 11:09 AM Re: Trim Tabs, Smart Tabs, Hydrofoil, Prop Questions. [Re: psycho0819]
gary purdy Offline
TFF Guru

Registered: 05/24/03
Posts: 11442
Loc: Littlefield Tx & Lake A. H. US...
Those 1978 5.0 motors were gutless. I have no idea how many 305 power boats and pickups I removed and put a 5.7 4bbl in. Later 5.0 are a little better. Have put 19* High Fives on a bunch and 17* High Fives on others. Amsoil outdrive oil keeps the drive it cooler while running a whale tail.
_________________________
The world will not be destroyed by those who do evil, but by those who watch them without doing anything. Remember what He has done and remember that He is not done yet!-- GOD IS GOOD

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#12780094 - 06/04/18 05:38 PM Re: Trim Tabs, Smart Tabs, Hydrofoil, Prop Questions. [Re: psycho0819]
psycho0819 Offline
Extreme Angler

Registered: 03/27/05
Posts: 1562
Loc: Kaufman
Yeah, mine's no speed demon, that's certain. With the whale tail it popped right up on plane, just wouldn't let me trim up much once there.

I have experience with SBC's in cars and trucks (stock to moderately wild built), just not in boats. But I don't imagine running a 305 in a boat is any miracle cure for it's short comings. Sad thing is, the PO claims it had been replaced a year before I got it, and it's compression numbers and overall condition support that. Never made sense to me not to put a 350 in it at that point. As for the rpm I'm seeing, it's about what I'd expected. A stock SBC valve train usually peters out about 4,300-4,500 rpm, just not enough spring to close them fast enough. Eventually it will get replaced with a 350. A lot of little things to shake out before it gets there though.

So prop first? Even before trim tabs?

Like I said, I've never ran them, so I don't know the sequence on arriving at a setup for an I/O when I am basically starting from scratch.

_________________________
If you're not living on the edge, you're taking up too much space!

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#12780505 - 06/04/18 10:12 PM Re: Trim Tabs, Smart Tabs, Hydrofoil, Prop Questions. [Re: psycho0819]
Pat Goff Online   content
TFF Celebrity

Registered: 01/29/05
Posts: 5850
Loc: Marble Falls/Seadrift
Prop is always first.
Then the tabs if you feel the need.
Then go catch some fish.
_________________________
Pat Goff
Marble Falls/Seadrift TX



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