1988 Mariner 115 HP / Inline 6 / Whale Tail

MikeCustomBaitPainter

Petty Officer 3rd Class
Joined
Feb 10, 2012
Messages
81
Any thoughts , Purchase the boat in Feb

1984 Stratos with 1988 Mariner 115 HP / Inline 6 / Whale Tail / Rapture ss prop , jack plate

I can't see any numbers on the prop ,

With the whale tail , Boat gets on plane find , wot running 45mph @ 5200 , whale tail is below the water line , major drag , plus eating up fuel ,

Without whale tail , boat fights to get on plane , wot running 49 @ 5500 , but when I back off wot the boat Porpoises really bad ,

Help with any ideals on setting the boat up correctly ,

Thanks Mike P.
 

aussieflash

Lieutenant Junior Grade
Joined
Feb 5, 2011
Messages
1,004
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

Got any pics of your setup?
 

RogersJetboat454

Commander
Joined
Jul 9, 2010
Messages
2,964
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

Most folks here recommend using trim tabs as opposed to whale tales, but it would be nice to see pictures of how your engine is mounted.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,033
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

Mike, I think you will find the prop pitch to be 19". That sounds about right for the speed/RPM you are seeing. You might put a straight edge on your hull and see if she is true. You do have the motor tilted all the way down, right? The transom is at a right angle to the hull, right?
 

MikeCustomBaitPainter

Petty Officer 3rd Class
Joined
Feb 10, 2012
Messages
81
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

Heres some pic's of the boat , I did measure prop to shaft , prop is 7in's below the pad.
 

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Charlie61

Petty Officer 1st Class
Joined
Jul 27, 2011
Messages
253
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

Any thoughts , Purchase the boat in Feb

1984 Stratos with 1988 Mariner 115 HP / Inline 6 / Whale Tail / Rapture ss prop , jack plate

I can't see any numbers on the prop ,

With the whale tail , Boat gets on plane find , wot running 45mph @ 5200 , whale tail is below the water line , major drag , plus eating up fuel ,

Without whale tail , boat fights to get on plane , wot running 49 @ 5500 , but when I back off wot the boat Porpoises really bad ,

Help with any ideals on setting the boat up correctly ,

Thanks Mike P.

Sorry but what is a "Whale tail"
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,033
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

Mike, The motor looks a bit high up. You do get to raise it up with the jack plate's setback, but it may be up too much. Why not drop it a bit and see if that helps. I could not see the length and type of boat. You may be overpropped for that boat.
 

MikeCustomBaitPainter

Petty Officer 3rd Class
Joined
Feb 10, 2012
Messages
81
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

Charlie , a whale tail helps your boat get on plane faster as/well stops your boat from porpoising. Its mounted just above the prop & looks just like a whale tail.

Mike
 

MikeCustomBaitPainter

Petty Officer 3rd Class
Joined
Feb 10, 2012
Messages
81
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

Chris ,

its a 1984 stratos , 18 ft , when I drop the motor down , should I remove the whale tail??

Mike
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,033
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

Mike, I never liked whale tails. I would remove it and see what kind of performance you get. A stern heavy boat will probably benefit from the WT, but with that 300# motor, your boat is probably not stern heavy. Check the WOT RPMs. Prop to get them into range, and see what hole-shot is. Then install the WT or not as makes sense.
 

redjmp

Chief Petty Officer
Joined
Mar 16, 2005
Messages
536
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

If your whale tail is still in the water at planing speed, your outboard is mounted too LOW!
By your pictures I can see that it is mounted in the lowest position possible.
You need to get more of the leg out of the water.
The whale tail creates a lot of lift which helps get out of the hole quickly but needs to by totally out of the water on plane otherwise its a big drag.
As such they are only good on outboards!
And then only if adjusted correctly.
Try raising your motor up a hole to start and keep going higher until the prop cavitates under load then back down a hole.
However, I don't see any whale tail...
 

MikeCustomBaitPainter

Petty Officer 3rd Class
Joined
Feb 10, 2012
Messages
81
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

Red ,

I removed the whale tail when I measured prop to shaft today & took pic's while it was off , its back on , I'll work on getting the motor up.

Since I haven't owned a boat for sometime , are you talking about raising the motor using the manual jack plate ?

Thanks for your in-put
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

What do you use the boat for? Sking/tubing or fishing? The pic's you posted of set up height is about correct for a all around ski/fish set up as its not enve close to being high. If you just fish and want a little more speed raise engine about 2"
 

Charlie61

Petty Officer 1st Class
Joined
Jul 27, 2011
Messages
253
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

thank you gi are great , my boat plane great when it's running
 

MikeCustomBaitPainter

Petty Officer 3rd Class
Joined
Feb 10, 2012
Messages
81
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

I only fish out of the boat , I know the in-lines eat gas , I don't even run wide open , trying to set the boat up right & save fuel.
 

Fed up

Petty Officer 2nd Class
Joined
Apr 30, 2010
Messages
189
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

I might be able to add some thought here. I have a 16 ft Champion, same motor, mostly same set up. Havent yet installed the jack plate. Mine came with a whale tale, and it took a while before I ever took it off and tried it. Heres what I found.

Whale tale- trimming out while on plane is touchy, but the hole shot is scary fast.
with out- trimming on plane is smoother, but will purpose slightly at high speed. The hole shot sucks, My ob trims down to where it is at an angle which should keep the nose down. but it doesn't, and is really noticeable if you are running about 1500-2000 rpm it wants to reach for the sky.

To the op, I dont know where your fuel tanks are on that boat, but with mine I have duals that are under the deck right infront of the motor, and with a full load of fuel and two people I really had rather run my whale tale.
 

MikeCustomBaitPainter

Petty Officer 3rd Class
Joined
Feb 10, 2012
Messages
81
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

My fuel tank is under the deck in front of the motor as/well , I'm going to raise the motor 2 in's up , try & get some of the drag from the whale tail out of the water , the boat does run better with the whale tail.
 

redjmp

Chief Petty Officer
Joined
Mar 16, 2005
Messages
536
Re: 1988 Mariner 115 HP / Inline 6 / Whale Tail

Red ,

I removed the whale tail when I measured prop to shaft today & took pic's while it was off , its back on , I'll work on getting the motor up.

Since I haven't owned a boat for sometime , are you talking about raising the motor using the manual jack plate ?

Thanks for your in-put
Well I would use the jack plate to get it set up for the best height, measure it and then I would be tempted to remove the jackplate and save the weight and just bolt the engine directly on the transom.

I can see that you have a tunnel hull at the transom. You need to raise the motor even more to compensate. That is probably why there is a jack plate...
 
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