1998 Mariner 150 Mag EFI -> change from 20" to 25" ?

4winnsskipper

Petty Officer 1st Class
Joined
May 9, 2007
Messages
204
Greetings

Im wondering if mercury sells a "kit" that would make my 150 mag efi mariner 1998 model year engine a 25" instead of a 20" transom setup?

Reason being is that when at dock, theres only roughly 4-5 inches of clearence between the water and the top of the transom where the motor mounts. The transom then raises up even higher the rest of the way to the side of the boat on both sides, but in decent waves, 1 - 2 footers water will occasionally come over the transom into the splash well..literally come over, not just "splash". While i understand it would take some decent waves / water to sink my boat, it still isn't comforting to see this happening. The boat is a 1800 sylvan elimantor...very deep boat, but they elected to use a 20" transom which STINKS. a 25" would of been perfect). The boat is rated to a 150 which is what i have. Of course when i bought the boat i never thought about the transom height, but lesson learned.

What im thinking of doing, if such a kit exists to make my engine a 25" shaft, is to install a jack plate using the holes existing in the transom, then mount the motor on that with a 25" shaft, then using the jack plate raise the engine ~5" so the drive is properly positioned again. Once this is complete i could then weld in some aluminum sheeting to cover the drop in the transom where the motor use to mount, which in turn raises my transom another 5" giving me near a foot total from water to top of newly raised transom. Since the transom was designed to be 20". the additional 5" i would fabricate wouldn't need to be load bearing since it's just acting as a splash guard essentially...

Thoughts? I will attach pix later tonight if that helps. All this rides on whether or not they make a kit...which i kinda doubt...
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,923
Re: 1998 Mariner 150 Mag EFI -> change from 20" to 25" ?

They sell a 5in extension.You need to remove the lower and remove the studs and replace with longer studs.
What's the serial#.I might have the extension you need.J
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,035
Re: 1998 Mariner 150 Mag EFI -> change from 20" to 25" ?

in amplify on what Jerry said, you need a longer driveshaft, or an extension, the 5" spacer for the midsection and the longer studs, and a water tube extension. Those are a PIA to install.
 

4winnsskipper

Petty Officer 1st Class
Joined
May 9, 2007
Messages
204
Re: 1998 Mariner 150 Mag EFI -> change from 20" to 25" ?

whats the rough cost of the complete kits to do this?

motor is 1998 mariner 150 mag efi
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Re: 1998 Mariner 150 Mag EFI -> change from 20" to 25" ?

If you add a jackplate you may need to buy a longer steering cable, and if you add one that is 8" or larger you wont need the 5" extension. It may just be easier and cheaper to add a flexible curtian across the splashwell like backtroller have...

http://www.wavewackers.com/
 

4winnsskipper

Petty Officer 1st Class
Joined
May 9, 2007
Messages
204
Re: 1998 Mariner 150 Mag EFI -> change from 20" to 25" ?

If you add a jackplate you may need to buy a longer steering cable, and if you add one that is 8" or larger you wont need the 5" extension. It may just be easier and cheaper to add a flexible curtian across the splashwell like backtroller have...

http://www.wavewackers.com/

does adding a jack plate put more stress on the transom? i'd imagine the longer the jack the more stress that is placed, correct?? I was looking at a 5" plate which seems to be the shallowest and hopefully wont need longer steering cable.

also im looking to not just block some splash but as stated in 2-3 foot waves water comes over the transom it sits so low.

..........or am i just being paranoid and this is normal to have waves come over then drain out over and over??? .............previous boat was an I/O so this is a new concern for me.
 

Attachments

  • boat 002.jpg
    boat 002.jpg
    142.8 KB · Views: 0

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,923
Re: 1998 Mariner 150 Mag EFI -> change from 20" to 25" ?

After seeing the pic.The more you lift the motor the more strain.I'd just add some plexiglass or like Fazt says some lexan.But I'll sell you the spacer and the drive shaft cheap:) J
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Re: 1998 Mariner 150 Mag EFI -> change from 20" to 25" ?

does adding a jack plate put more stress on the transom?

No.. it just changes the center of gravity of boat or leverage point as some people call it.
or am i just being paranoid and this is normal to have waves come over then drain out over and over???

It is normal to take a few waves in splashwell but you have a kicker on the rear which weighs about the same as a type 27 trolling battery. I myself wouldnt worry about it but if it did cause me a concern I would install a backtroll kit. In these 2 ft waves I would worry about the kicker being dunked,as I have seen them locked up as water was forced up exhaust tube into bottom cylinder from wave actions...
 

j_k_bisson

Lieutenant Junior Grade
Joined
Oct 6, 2010
Messages
1,082
Re: 1998 Mariner 150 Mag EFI -> change from 20" to 25" ?

Bay Manufacturing out of Ohio makes factory authorized extention kits. Hell Yamaha does not even make them them selves anymore. They order them from this company. They run about 500-700 full kit. The kits include stub shafts for the drive and shift along with the housing spacer. They are not painted. You will need to do this yourself. These are fully engineered, so they work!

Here is the link

http://www.baymfg.com/

Hope it helps.
 

4winnsskipper

Petty Officer 1st Class
Joined
May 9, 2007
Messages
204
Re: 1998 Mariner 150 Mag EFI -> change from 20" to 25" ?

Thanks guys im gonna try some a home mode lexan setup first then i may try this if that doesn't do it

Im also gonna add scupper valves too since those ssuckers since right near the water line already.
 
Top