New member revived an old Mariah
 

Hello to all!
A few months ago I picked up a 92' Diablo for a song. The boat was somewhat neglected but not abused. This is far from being my first boat so I knew what to look for and other than the drive being trashed from the previous owner dragging it up the launching ramp, and a ton of cosmetic needs, I saw a diamond in the rough.
I got the trailer work done, and all the mechanicals done and went to town sanding, compounding, polishing and waxing in the last few days (If I never hold that buffer again it will be too soon!)
After getting the new drive installed and doing a complete service on the engine (4.3), I took it out for a shakedown run. The first thing that struck me was that these boats are well built. It had a SS 19" prop on it, but during the initial run it planed and revved quickly to 47 mph but was turning 5400 and still climbing when I backed it down. I ordered a new 21" TP Hustler and installed it yesterday (Hopefully this will be a good choice as I can't imagine needing to jump to a 23"..lol)
Tomorrow will tell on speed and rpm.

Re: New member revived an old Mariah
 

Deja Vu :eek_animated:
That thing looks awfully damn familiar.:rolling_laugh::rolling_laugh:
Congrats and welcome to MOC amp! :)

Re: New member revived an old Mariah
 

Welcome and congratulations on reviving that Mariah! You said it reached 5400 rpms with room to keep climbing? First thing i would do is check that tach. With a 19" prop you shouldn't see anything more than 5000- 5100 and normally with a 21" pitch you wont have much in the way of hole shot on a 4.3 There's a small dial on the back of the tach marked 2-4-6-8. Give it a few spins and then re-set it to 6 cyl and see if that makes a difference.

Re: New member revived an old Mariah
 

Thanks guys.. Will do on the tach check!

Re: New member revived an old Mariah
 

There is also a calibration screw but you need a reference tach to set it with

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Re: New member revived an old Mariah
 

Well, with the 21" Turning Point Hustler installed.. the boat (trimmed and on smooth water) ran 50mph (gps matched the speedo almost exactly) and turned 5100rpm yesterday. It was just my son and I, half tank of fuel and no extra gear. After verifying those numbers on a prop calculator (Showed .13 prop slip) Those numbers seem to jive? Also with this prop, the boat was able to stay on plane down to 2900rpm and the "perfect" cruise seemed to be right around 3600... Smart tabs will be here Wed :)

Re: New member revived an old Mariah
 

Your gonna love em on the little "D" :yes_grin:

Which ones did you get ,the SX or the ST series?
I put SX series on mine and love them.:wink_thumbup:

Re: New member revived an old Mariah
 

The rpm's are still high, particularly for a 21" pitch prop but if its working and you're happy with the way it performs that's all that matters. :wink_thumbup:

Re: New member revived an old Mariah
 

CD, I ordered the SX, and I'll have to mount mine just about like you did. Mikey, I know that's still high, but I figure with the slight drag from the tabs, 4-5 people, gear and a full tank of fuel, that should put me right at the top of the recommended range (which should be perfect for tubing) .. don't you think? Btw, I spun the selector on the tach and then back to it's original slot. It's a Faria and seems in pretty good shape.

Re: New member revived an old Mariah
 

Hey CD, I almost forgot... What setting on the tabs worked best for you? Nauticus recommended the 80s', but after reading all the posts, I ordered the 60s'.

Re: New member revived an old Mariah
 

Again, if it works and you're happy with it, dont screw with it. ;) Just dont run it at WOT for any length of time.

I would set the Smart Tabs in the middle position to start and see how the boat reacts. Its easy to change the position afterwards.

Re: New member revived an old Mariah
 

One down from middle is where mine is , but it is kinda user preference.
As Mikey said , start in the middle and see what you like.:)
Watch your WOT , and that will give you the sweet spot as far as top end.

Re: New member revived an old Mariah
 

Update: Installed the Smart tabs SX and tried the 3rd (middle) and 4th (firmer) positions. These things work great, but actually went back to the middle position. Set on the 4th notch, the boat was almost TOO stable (if that makes any sense..lol). I also ended up having to order a 23" prop. I went with another Turning Point Hustler as I already bought the hub kit with the 21. I'm now topping at just over 54 mph at 4850 rpm and the engine sounds much happier. I ordered a new tach just to be sure, but the increase in speed is telling me what I think I already knew. I have to tell you guys, I can't imagine this engine with a 4bbl (LX). WOT over a bit of chop, and trimmed to the max sweet spot and this boat is scary fast and "trying" to become an aircraft! LOL