Sea Ray 390 trim tab mods.

C

CRay

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Joined
Mar 9, 2011
RO Number
32502
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89
First year with my 1986 390 Express, 350 HP Crusaders (900 hrs) that run great but need to get up to 3400-3500 rpm at full tab to get "over the hump". Anyone have experience with modifying the tabs from the stock 28"(at the hinge tapers to 23" at the trailing edge))X 12" Bennett tabs to improve performance? Thinking of installing 28"X16" tabs with turned down edges to hold water on the tabs. I was spoiled by my last boat, 32' express with 30"X12" Bennett's that would come on plane with 0 bow rise (if I wanted) and stay on plne at 14 knots. Don't expect to get that on the 390 EC but would like to 18-19 knots at 3200 rpm with little bow rise.
 
I would have to do the same thing with my 34' . But them after she got up, I could pull back and cruise nicely at 3100-3200 rpm. BTW I had the same engines in my 34' which is much smaller than the 39. So I see no problem.

You have to spin up the props faster while your climbing out or you will never get there,
You don't want to take all day getting up on plane as your engines will hate you for it.

....so wont other boaters, and the guys fishing in dingys you cant see.

Nail it, ....... get up and out then trim her nicely and cruise.
 
Did you have outdrives on your 32'? My 34 was V drives and shafts... You got shafts now and tunnels. Different world.
 
That 1986 to 1988 390 series are notorius for slow getting on plane. Those big blocks just don't have enough oomph to get her up fast. Loved that boat, but it was underpowered. Should have had diesels.
 
quote:
Originally posted by JLC

Did you have outdrives on your 32'? My 34 was V drives and shafts... You got shafts now and tunnels. Different world.

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Actually the boat was a 32 ft Starfire Westport with 260 hp Mercruiser inboards and 1.5 Walter V Drices ans 17X15 three blades. Best handling boat I've ever been on. Don't expect that from the 390 but will try to get closer.
 
I extended the tabs on my 330 for the same problems you describe. I could not widen the tabs due to the tunnels, so I did a little layman's engineering to get the correct square inches recommended by Bennett and my 22*9 too small tabs are now 22*18. All the difference in the world. It's like a different boat. The mod also cut my fuel consumption.
 
You can tab across your tunnels , I'll give you special permission.
 
Give bennet a call.

Turning down the edges will also stiffen the tabs if you wanted to lengthen them. You might even be able to double up the rams if you have room to widen them. There are a lot of possibilities...but there are limits to what you can accomplish.
 
quote:
Originally posted by RWS

This thread from the Trojan website should be helpful:

http://www.XXXXXXboats.net/wforum/viewtopic.php?p=33713&sid=740bd5781e32c61c8de097dd6f976d11

RWS

.......sorry no links to other forums permitted........rules are rules.

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==========================================

Sory about the link, I dun fergot.

There is some very helpful, detailled information on a website that is devoted to the Trojan brand.

You will be able to find it by using a search engine like Google or Yahoo or Bing.

Try Trojan "trim tabs" RWS

Lots of specific info over there.

My apologies to all regardingthe rules, now I will go back and stand in the corner.

Do I really have to wear this silly, pointed hat?

RWS
 
I left the word Trojan.......I figured he would replace the XXX's with Trojan....and get there. :)
 
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