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Steering fin

HavAZd

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I bought a 73 Spectra 20 with a BBC jet. I've only had it out once and found that the front end wanted to 'hunt' at or near full throttle. The steering fin is a bit twisted. I am re-doing the floor and gas tanks so I took the fin off yesterday too since I had access.

Is that something that I should have on the boat or should I just fill the holes and call it good. This is my first jet, only previously had stern drives. The boat goes under 60 mph.

Thanks
 

Just Electric

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if your talking about the drop through or bolted fin under the boat just in front of the motor i would put it back on.with out it your boat is not gonna want to turn(meaning it pushes )and being a jet it dosent want to turn anyways.
 

Skee

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I bought a 73 Spectra 20 with a BBC jet. I've only had it out once and found that the front end wanted to 'hunt' at or near full throttle. The steering fin is a bit twisted. I am re-doing the floor and gas tanks so I took the fin off yesterday too since I had access.

Is that something that I should have on the boat or should I just fill the holes and call it good. This is my first jet, only previously had stern drives. The boat goes under 60 mph.

Thanks
My Spectra does the same thing...I have heard this is one of the "characteristic's" of these Spectra's....I would get it straightened and put it back on,definately....
 

jetboatperformance

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I bought a 73 Spectra 20 with a BBC jet. I've only had it out once and found that the front end wanted to 'hunt' at or near full throttle. The steering fin is a bit twisted. I am re-doing the floor and gas tanks so I took the fin off yesterday too since I had access.

Is that something that I should have on the boat or should I just fill the holes and call it good. This is my first jet, only previously had stern drives. The boat goes under 60 mph.

Thanks
Sounds like the boat may be "Bow hunting" or bow steering , that boat is is little heavy in the front end , there might be some adfjustment for this in the ride plate (if equipt) also is this with the jet trimmed "up" (trim?) Tom
 

HavAZd

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Sounds like the boat may be "Bow hunting" or bow steering , that boat is is little heavy in the front end , there might be some adfjustment for this in the ride plate (if equipt) also is this with the jet trimmed "up" (trim?) Tom
I actually don't have a ride plate or any trim control. The bowl is also the older style one piece, not a split. That particular ride was on smooth water, only two of us in the boat and not a bunch of junk (ice chest, anchor, etc). There was no gas in the left tank and about 15 or so in the right. There was nothing stored in the bow area.

The fin that was on it bolts thru the keel.
 

RiverDave

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Just order a new fin up, and put it on. I don't think you want to get rid of that.. On a jet (I'm no expert so take it for what it is) on a cruiser that big, I think you'd really want to run a rudder as well.

RD
 

BarryMac

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Replace the fin. It helps a ton in slow steer, like when you're putting back on the trailer and such... Just my .02
 

HavAZd

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OK, I'm convinced to replace the fin - now if I could find a direct replacement! The fin I have is bolt thru, 9" long and 4" deep. The fin at Rex Marine is longer and deeper (6.5" deep I think).

Do they even make bolt thru fins any more. The few that I have found say they are "drop thru". That sounds like a whole new installation challenge for me. :grumble:
 

92 cole

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I would deffinetly reinstall a new STRAIGHT fin. Installation is no biggie just do some measuring to assure it is straight to the bottom. Also if you go deeper be sure to check the fin to trailer clearance at launch time!!! If the old fin is tweeked from the back could have been the problem in the first place. Trying to launch to shallow! Ah yes bow steer on an older cruiser, common problem and easily fixed! M
 

RiverDave

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OK, I'm convinced to replace the fin - now if I could find a direct replacement! The fin I have is bolt thru, 9" long and 4" deep. The fin at Rex Marine is longer and deeper (6.5" deep I think).

Do they even make bolt thru fins any more. The few that I have found say they are "drop thru". That sounds like a whole new installation challenge for me. :grumble:
Do'nt quote me on it, but I think attwood makes em. I think you said you have a spectra. If you do Danny at DCM can probably get you the right fin, as he installs those type on his boat (same hull)

RD
 

Flat Broke

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You need to take a step back and clarify the term "hunt" a bit. The reason I say that is because a stock Spectra 20 does not create enough transom lift to cause bowsteer. When you say "hunt" do you mean the steering is not precise and at speed the boat will require active input to keep the boat on a specific and exact course; or do you mean the bow of the boat is aggressively engaging the surface of the water and pulling the boat based on the contours of the water's surface? The former is a characteristic of jet boats in general(but it can be mitigated/reduced), while the later is an actual handling problem.

In the instance of the first characteristic, yes a fin will help. They're made by Glenwood. Do a search for Glenwood fin and you should find specific part numbers cited by Danny.

If the problem is more along the lines of the second scenario described. You need to find out why the boat is bowsteering. Spectra 20 jets don't exhibit this behavior in general. Typical causes for bowsteer are hook in the rear of the hull's running surface, excess weight in the bow, or excessive negative trim.

To check for hook, lay a 4' straightedge on the bottom of the hu starting at the transom. If hook is present, you will see daylight between the straightedge. If this is the problem, the most efficient fix is to remov the hook with bottom work.

If no hook is present, weight or trim must be the culprit. Since yo can't ru wedges with your bowl the only variable is an incorrectly set intake adapter. STD Berk adapter have 4* of negative trim or downward thrust angle. If the intake wasn't set level and is infact installed nose up, the effect is the same as adding negative trim or vectori g the thrust downward.

If your intake is installed correctly, the last remaining variable is weight. I dint think a 73 would have had foam sprayed under the floor. Nonetheless, check for waterlogged flotation foam forward of centerline, or if your boat has a belly tank(not factory in 73), the tank is likely positioned too far forward.

These are things to check as your setup is about as simple as it gets with regard to the pump.

Good luck with it,
Chris
 

HavAZd

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What I referred to as hunting was the boat would want to go a little off course, both left and right, at near full throttle or about 50+, feeling a bit squirly. The water was smooth and there was nothing really in the boat as far as gear. It was only at or near top speed.

I have the floor out and you are right, there is no foam and it had gunwale tanks.

I took my fin to a local prop shop and they say they can repair it. I'll see. A search for glenwood fin revealed there is a Fin Bar in Glenwood Springs, CO. :drnkfr

I'm going to get the fin, floor, and new tanks in soon so I can use it here shortly. I will then find out exactly what other issues I may have when it's loaded for use and how it rides and skis. If I get the inside done this spring I can work on the other issues next winter (or as required during the summer).

I won't be able to afford any Place Diverter or trim this year but...

Thanks for the input.
 

jetboatperformance

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What I referred to as hunting was the boat would want to go a little off course, both left and right, at near full throttle or about 50+, feeling a bit squirly. The water was smooth and there was nothing really in the boat as far as gear. It was only at or near top speed.

I have the floor out and you are right, there is no foam and it had gunwale tanks.

I took my fin to a local prop shop and they say they can repair it. I'll see. A search for glenwood fin revealed there is a Fin Bar in Glenwood Springs, CO. :drnkfr

I'm going to get the fin, floor, and new tanks in soon so I can use it here shortly. I will then find out exactly what other issues I may have when it's loaded for use and how it rides and skis. If I get the inside done this spring I can work on the other issues next winter (or as required during the summer).

I won't be able to afford any Place Diverter or trim this year but...

Thanks for the input.
I have fins and tanks for that matter, (Glenwood and others ,new and used in stock ) and occasionally have used diverters and jet0Vators call or PM if you need help or have questions Tom
 

CHROMEY

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send up some pictures of your floor replacement, i may need to change mine out at the end of the season, looking for some photos on this....
 
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