Having major issues when adding people in the boat. With 2 guys, the hammer prop runs 30.2mph. Add a guy to the boat (3), and the prop bites for a couple seconds and then totally blows out and cavitates. By myself, GT 10p 3 blade runs 28.5mph. Add a guy to the boat (2), and the prop bites for even less time than the hammer does, spins out, and cavitates. Have tried absolutely everything. Adjust trim, try to accelerate slowly, changed the pin to every hole... Nothing makes a difference. At this point, I'm thinking I just need an absolute monster prop. But, please, somebody that knows what they are talking about when it comes to pitch and cup, help!!! LOL

More or less pitch... What does it do?
More or less cup... What does that do?
2 blades compared to 3 blades... Why does it make a difference and theoretically, what does more blades do?
Bigger (longer) blades compared to shorter blades... How big (long) is too big? Having the blade spin below the skag?

I have been told a GT 11p 3 blade should work, but I'm really questioning whether it will or not at this point, based on the fact that the hammer is an 11p and is bigger and I already know it doesn't work. I have tried the two props I have access to and will now have to purchase another or have work done to what I have. I would like to avoid having to try too many more different props and need to get this situation solved ASAP.

HELP!!! I am completely frustrated. Thanks!

Sounds like the motor might be a little too high. Have you checked the transom height? It may be too tall.

21"

I think it needs to be 20" .

The problem is something with the boat. There's lots of people with strong motors that don't have this problem.

How are you measuring down from the top of transom down to a straight edge on the bottom of the boat.

Yep mine is 20"

Definitely need to make shure your motor is at the right height on the transome before doing anything else, if it is the the prop u need to add cup to stop cavitating and pitch to lower RPM's, say your on step running wot and you have to have the prop submerged to stay off rev limiter then u need more pitch , if it runs good once your on step then add cup to stop the cavitation. But adding cup will drop RPM's also. 3 blade would be my choice. Should give you better overall proformance!

I'm not much of an artist, Mike. But, this is how I'm measuring.

Have you tried with everyone sitting as far back as they can? In your avatar it looks like you could have a lot of bow weight.

Well that's exactly how mine is.

Have tried moving people everywhere. No difference. The boat is HEAVY! But, weight is distributed well. And, odd that it can run 30mph, then add another guy (no matter where you sit him) and it won't bite for nothin'.

You need less pitch.


Most liberals seem to suffer from the same mental condition....it's called stupidity!

Where u located I've got a handful of props that I can let u run if ur not far

LOL... Indiana... Would guess you're far.

Might have to cut your transom down 1/4".

If I need less pitch, shouldn't the gt 10p 3 blade have worked better than the 11p hammer?

Im thinking it's the transom If it's doing it with both those props which are the complete opposite of each other.

Have you called GT to get their opinions?

It honestly gets on step for all of 2-3 seconds and then it loses bite without me changing anything throttle wise.

Every prop runs different on different boats. What works for some may not work for u. Jus have to try few different ones out an see where ur at. As stated above it may be ur transom

From that drawing, do you think that an inch needs to be cut off the transom?

I think they say 20" and 17 degree angle is best for GTR. is that 20" at the front of the "plate" or on the back? And I'm pretty sure my transom angle is 18 degrees.... Would that make a huge difference?

And, no, Mike... I have not discussed with GT.

20 degrees is optimum but that's for digging purposes. There's quite a few that run production boats with 16 degree angle without your problem.

I'd cut down 1/4-1/2" till you get it right.

Just my little input. This is why I ran hydro. Jack plates on my dual rig which was very heavy. When I had a lot of weight in the boat I would adjust the motor height for the weight.

GT may have run into this problem before and might have a quick fix. That's why I was asking.

Cmc hydraulic jack plate.

Is it possible for me to run a jack plate on mine w/tiller?

Yeah just have to mount the switch somewhere for raising it up and down. Thing is its a 900$ trial and error might work and might not. I just know they helped a lot on my dual rig. Maybe see what others input might be. I know terry b is running Jack plates on his dual rig maybe he knows if it would help your situation.

If I did that, would I need to cut the transom down first?

Way cheaper to add cup to the prop. That's a lot of motor for a stock prop

And, like Mike said... Yeah, its alot of motor, but alot of other guys have really strong motors and don't have cavitation issues like this.

Mike,

If I were you I'd cut the transom down 1/4" at a time going no more than 1". This will be the cheapest route I think. You can always weld what ever you cut off back.

If you play the prop game I think you will spend money to work a prop then find out that's not your problem and have another prop u can't use and have to spend more money getting it back to where it was.

The Jack plate idea may work but now you have the added cost,weight, and motor moved back an additional 6" or so.

Another reason I don't think it's your prop is because Jamie has a pretty strong engine and he turns a 10p 3 blade about 5400 and I turn it about 5100 without your problem. I know our boats are different but....

Just a thought, but are you sure your clutch isn't slipping a little once the third person is added? You would think that if the prop has bite with two on board that it would draw the rpms down with three. I wouldn't think that transom angle or height would the end all to the situation.

My boat was doing the same thing with a really big load where it would rev up to 4500 and not get on step and all I did was add pitch and problem solved, but I had already added cup and the boat did fine with a light load but I had to keep it trimmed deep at wot, my original thinking was that less pitch would push harder but when I added modds it would just cavitate because there wasn't enought pitch to bite the water.