More power from 25HP Mercury?

Question
We own a 16' Alumacraft deep/wide (Lunker V16, tiller steering) with a 25HP Mercury motor, this is a great fishing setup.  When the kids were younger we bought a towable tube (60") and they had a great time.  As they've gotten older, and heavier, the ride is 'less radical'.  I'm wondering if there is anything you could recommend to get some increased pulling power from the motor.

The current prop is an aluminum 3 blade 11 pitch.  I've thought about going to a S.S. 3 blade 13 pitch or maybe an aluminum 4 blade 11 or 13 pitch.  I'm guessing the 13 pitch will loose a little on the top end, but might give us more pulling power (or does it work the other way around).

I've opened the main jet 1/4 turn past the factory setting and am getting about 30MPH w/o the towable.  My fear is if I open it any more there's a chance of burning out the piston.  Is this a justified fear?

We've also been told a larger diameter towable would provide less resistance as it spreads the weight 'thinner'.  We live on a 150 acre lake connected to another 200 acre lake and I really don't want to spend money on a larger motor unless it's my only option.

Answer
Hi Don

Thank you for selecting the undersigned to reply to your question.

First of all, I get the impression your youngsters are now adults, hence the increase in weight within the water tube.

Opening the fuel jet on an already beleagured engine might cause more harm than good results, or bring about costly repairs or its early demise.

Changing the prop's pitch & diameter will give you an advantage when starting up, but don't be disappointed with the top end performance. You need to experiment with a few props to see which one actually works best for your purpose(s). Most marinas have used/rebuilt props to offer for testing, before making a purchase.

A 5' diameter tube is quite huge. A larger, wider water tube may be a partial solution, but keep in mind, an expanded diameter means more friction area, which in turn causes resistance - versus disbursing weight load over a wider surface.

And, there's no need to switch boat models, your's is just fine for all purposes described. Test some props first. It might surprise you, and the cost will be warranted. Reduce the diameter but increase the pitch within the engine manufacturer's parameters.

Safe Boating
Ron