1999 Glastron SF180 Performance

[GlastronSF]

I have a 1999 Glastron ski and fish (18ft long). The boat is fantastic and has a 1999 Mercury 125hp outboard ELPTO. I am wondering how much additional performance I would really get out of the boat by putting a 150hp motor on? The boat is rated for 150hp but with the 125hp I can still pull 50mph out of it. The 125 is a 4 cylinder. Any advice? Do you go larger than rated?

 

[stubbsboogie]

Re: 1999 Glastron SF180 Performance

Do not go over the rated horspower...
all sorts of various issues, liability,safety, illegal ect.

I had a 1998 GS180 I doubt you will get much more performance out of a 150 maybe 4 to 7mph but thats it I think. Over 50 is plenty to me.

 

[mike343]

Re: 1999 Glastron SF180 Performance

I guess it's up to you if the 3-5 mph is worth it--maybe 15K (new) installed. Is the hull at all tender at 50 (and is it pitot tube or GPS measurement?) 50 seems a little high for your rig.

 

[Philster]

Re: 1999 Glastron SF180 Performance

Doubt your getting 50 now.

Not worth repowering for a couple of MPH. If the boat was boat new, I'd have gone for max HP, but bumping up later just ain't worth it.

Engine HP is rounded up/down. You might not even get a 25 HP jump. It might only be 15 HP, and that is worth almost nothing.

 

[GlastronSF]

Re: 1999 Glastron SF180 Performance

I bought the boat last year, I am the second owner. The boat is so clean it is like new (and I am very picky). The motor upgrade is just a question that rolls around in my head.

Speedo - it has two. one std. pressure driven through the foot of the Merc. and the other is a magnetic paddle wheel through the Hummingbird.

The boat does do 50mph. I was surprised myself but with me in it, calm water and the trim up it hovers along with a slight waver and feels totally solid. The hull has a bit of that flat are in the center back end, same as found on the Larson Flyer.

The bigger motor I thought would help when we have more people in the boat or are skiing. My motor has extremely low hours (maybe 200 to 300) and looks like new. Didn't know if I sold it and bought a used 150 Optimax how much I would really be out $$.

 

[cribber]

Re: 1999 Glastron SF180 Performance

Cheaper alternative is to test various props for what you'd like to do. 50 mph on your setup now would be your baseline. I'd validate your measured speed against a GPS unit though. Then figure out what ya want... 50 mph water skiing is scary for most folks. Being able to pull a couple of skiers or tubes at 35 mph is much more fun. I have a 4 blade SS for a full load. Lost a little off the top end but holeshot and mid range stability are fantastic with a full load.

I contemplated the same thing about upping the horsepower and found the sweet spot I was looking for by tweaking what props I run. BTW... I have 3 props that I use depending on what we're doing. Only takes about 15 minutes to swap out props in the driveway.

 

[GlastronSF]

Re: 1999 Glastron SF180 Performance

Funny you mention props. I just made a post about props. I have two with the boat. one aluminium 21 pitch and one 18 pitch SS (mercury vengence). Would a four blade or five blade work with my motor (125 two stroke)? And what difference do the extra blades make?

If you had an 18pitch 3 blade what would you go with in a four or five blade

* you are right about not focusing on my top speed. but more focusing on stabalizing that 30 to 40 mph range.

 

[mike343]

Re: 1999 Glastron SF180 Performance

Unless 50+ is your goal, multiple props are the best idea for a small boat with light to heavy loads on board at different times. Also paddle wheels and pitot speedos usually read high at high speeds. Find a friend with a GPS and confirm your baseline. You may be surpised, but maybe not.