Logo
FULL SITE MENU

25/20 Mariner Jet performance

J

JamesNeidig

New member
Hello everyone. I am new to the site so forgive me if I'm in the wrong place. I have a 1998 Mariner 25/20 factory Jet tiller on a Sea Nymph 1648MV. Motor seems to run really well, however I am new to jets and set up and would like someone to weigh in... Keep in mind, I am coming off of a Triton TR186DC with a 175 Merc... Now I know this is nowhere in the same league but here's where I am...
With my son and I (I am 180lbs and he is about 60lbs) the boat planes and runs about 16mph on GPS. If I add one more adult, it will not plane and basically means I need about 10 to 12 inches of water to run in. No big deal in the summer, but fall walleye fishing does not lend itself to getting out to pull it over skinnier water to reach the channels.
I have added a front deck and a trolling motor for a total of about 65lbs or so. I am in the process of moving the group 27 battery to the rear as when empty, the rear of the boat sits higher in the water than does the mid section and even more so when I am on the front deck.
I have checked the impeller and the clearance is good. I have also sharpened the edges. I have fully straightened the intake grates and even sharpened them to a near knife edge on both edges to help water flow.
I have been told that the 25HP Mariner power head is already maxed out for HP...not sure if this is true or not.
The boat is rated for up to 40hp so I assume i could go all the way to a 60/40 Jet but holy crap that would add a lot of weight and strain on her transom.
Any suggestions of things to try short of adding a bigger jet motor?
How do I know if I am getting cavitation? etc...
 
Here's picture of what it looks like. I have an eerie feeling my only option is a bigger motor here...
photo.jpg
 
kimcrwbr1 said:
A 40hp 2 cycle short shaft with power trim will get you up on a plane with three adults for about the same weight as your motor and when you get in the shallow just trim it up to keep the prop off the bottom. With just you and your boy it will fly.
Click to expand...

Are you referring to a jet with 40hp at the crank or pump?
 
So let me add this thought process. I may move the battery to the back of the boat, then redo my front deck in aluminum instead of the heavy high density polyethylene sheet. This will significantly lighten the front. Because I will have added weight to the rear, I am considering adding some beavertail pods to the rear. While I know the motor is the same, I should have the boat sitting much higher which will yield less drag. Make sense to anyone else? Thoughts? Experience doing it? Thanks!!!
 
If you add pods to raise the hull, those will "drag" and I think you will be "in the same boat".

You have quite a bit of boat, plus a bunch of added weight there that you are trying to move with the equivalent of 20 shaft horses with the added "slip" of the jet.

You can't hop up the 25 horse power head any, nothing really left to enhance that would make any noticeable difference/improvement.

Your noted speed of 16 mph is pretty much what I would expect the way you are rigged and how you are operating - sounds like everything is working as it should with that combo.

You are significantly "under horsed" for how you want to use it - no bolt on, add on, strap on, tie on, magic in a can, shifting of weight, adding appendages is going to get you what you are looking for.

You are either going to have to replace the motor or live with the limitations..
 
Thank you! Appreciate it!

The mods will essentially allow me to slip through some skinnier water without smacking the jet foot but if I want any additional gumption I guess I need to look for a 50/35 or a 60/40 jet with a tiller.

Thanks again for the feedback!!! Jim.
 
Last edited:
Back
Top