2007 Glastron GT185, need prop advice

[crazeejames]

Hi all,
Just got a new Glastron GT185, with the 3.0L Volvo Penta. It has about 5 hrs on it now, so I have opened it up a bit. It seems pretty sluggish out of the hole, we usually have 3-4 adults and 2 kids in boat and of course a full tank of fuel. It currently has a 14.25x21p 3 blade prop on it.
Trimmed out, it will turn about 4300rpm. I would like a prop that will work for this load, as well as pulling 3 person tubes, skiing, and wakeboarding. I would like to still be able to reach 40mph after the change. My dealer said maybe a 14X20P 4 blade is the ticket.......what do you guys feel would work, does any have one of these boats or similar?
Thanks.

 

[Tail_Gunner]

Re: 2007 Glastron GT185, need prop advice

Hi all,
Just got a new Glastron GT185, with the 3.0L Volvo Penta. It has about 5 hrs on it now, so I have opened it up a bit. It seems pretty sluggish out of the hole, we usually have 3-4 adults and 2 kids in boat and of course a full tank of fuel. It currently has a 14.25x21p 3 blade prop on it.
Trimmed out, it will turn about 4300rpm. I would like a prop that will work for this load, as well as pulling 3 person tubes, skiing, and wakeboarding. I would like to still be able to reach 40mph after the change. My dealer said maybe a 14X20P 4 blade is the ticket.......what do you guys feel would work, does any have one of these boats or similar?
Thanks.

If you go to a 4 blade id stay in the 18 pitch range or less, 4300 is 500 rpm less than your engine was desinged to run at. You should be running @ 4800

 

[Matt S]

Re: 2007 Glastron GT185, need prop advice

I have that same exact boat, now with 11 hours on it. I've been doing some research and calling around. First off, with 4 adults and 2 kids and just the 3.0L well..that's a fact of life. I'm pretty surprised just how MUCH the 3.0L moves the boat. But let's face it, it's not the 6 cylinder. You're just too heavy for the motor. Take it out with just you and a friend and you'll see a huge difference. I tubed with my boat this past weekend, and towing my large 250lb friend with 2 other large people in the boat (and me, average) was tough getting on plane. Make a few of the bigger people sit up front, it helps. Also, are you trimming up? Once on plane and up to speed, move the trim indicator up to the tick above the bottom, don't go above the larger black tick above that under heavy power. That range is for idle only.

So from what I understand going down a pitch raises rpm by about 250. A shop suggested I go with 14.25x19. That'll make my light load rpm's go up about 500rpm - past the suggested 4200-4800rpm so watch out. But from what I read it'll give me a better hole shot when towing a skiier with some people. You won't be able to hit 42mph - 45mph (my observations) with just a couple people. It'll be more like 35-40mph @ 4200rpm. I like to cruise about 4,000 rpm and I can deal with going 35 instead of 42 at that rpm.

 

[Tail_Gunner]

Re: 2007 Glastron GT185, need prop advice

It seem's old marble eye's is back.........let us see what the master has to say......

 

[walleyehed]

Re: 2007 Glastron GT185, need prop advice

Hey TG...whaz-up...
If you folks are mid range of the RPM now, going down 2" (in the exact same prop model/make), I really don't think you'll see 250RPM gain, (per inch)..150 to possibly 200, maybe.
You are going to trade speed for hole-shot and can't really get around that with an I/O.
If you stay with a 3-bld, I think I'd stick close to a 19...if 4-bld is an option, like TG says, an 18 should perform well...some are better than others and if going to 4-bld, I'd go SS.

 

[crazeejames]

Re: 2007 Glastron GT185, need prop advice

Well, I went and bought a 4 blade 20p michigan wheel(aluminum). Put it on this weekend, and I am very pleased with the difference. With 4 adults, and 2 kids on board, no problemo jumping onto plane, its as good as it was before with 2 adults on board. On the top end, I lost very little, trimmed I can get 40 with 4 adults/2kids, and 42-43 with 2 adults. Still not reaching 4800 rpm, but seems to be singing pretty good at 4500rpm. I may try an 18p prop for pure watersports fun and use this prop for an all around prop. I would definately recommend going to a 4blade 20 or less on this boat/engine combo, as I was disappointed in the performance of the boat before this switch.

 

[walleyehed]

Re: 2007 Glastron GT185, need prop advice

This is where the 18P in SS would shine...
It would drop your slip ratio (using a quality SS) You'd have tremendous hole-shot, get the R's up to 4800 where they should be and still have the 42-43 and probably WITH a load. Your mid-range economy would be increased as well just because the SS in 18 would be much more efficient than the 20 in aluminum.

 

[tmh]

Re: 2007 Glastron GT185, need prop advice

Crazee, you're getting close! A 21" Aluminum prop on that boat is fine...for showing you how fast it will go with no one on board! I'm surprised you added 200 rpm going to the 20" 4-blade.

Anyways, as all will tell you, props are always some compromise. With a somewhat underpowered boat, if it were me I'd avoid SOME of the compromise by having two props; and 18" 4-blade (or "High 5" 5-blade) for days when water sports dominate and a 19" 3-blade for general cruising, etc. SS if conditions in your boating area make that "safe" for the outdrive.

You need a back-up prop anyways, and most people make far to big a deal out of prop changing - takes me a few minutes while anchored shallow and the kids swimming around. No big deal.

 

[cribber]

Re: 2007 Glastron GT185, need prop advice

Glad to hear the 4 blade 20" pitched worked out. I have a 2008 GT185 with the Volvo 3.0l. I put a K&N filter on mine and noticed an improvement in hole-shot as well. I did this at the 20 hour service and the guy gave me a hard time until I showed him the SAE certification as a spark arrestor and then he moaned about sensors... You'll have to replace the stock carb stud with a stainless steel bolt since the filter, base, and hat are about 3 inches. BTW, this thing is mirror polished stainless and looks sweet sitting on top of the bright red engine. If you order it direct from K&N, don't forget the oil breather adapter.

 

[KM2]

Re: 2007 Glastron GT185, need prop advice

Walleyehead or others, can you make a recommendation (s) on a good 4 blade prop. It seems when I do research here I get lots of info on outboards but not much for I/O props.


I do have a 14x20 AL MW (w/hub kit) and it's ok for holeshot but I lost a lot of speed and can overrev easily. Plus it needs a rebuild I took a small chunk out of it last year.