Some prop advice please

[nooblet]

Hello everyone. I read the "read this first" sticky, so I will give as much of the information as I can.

I have an 18' Galaxy I/O boat. It has a Merc Cruiser 4.3L V6 Alpha drive.

We started with a 3 blade aluminum prop with a 19 pitch. My dad recently purchased a used 4 blade SS 19 pitch prop after the aluminum one fell victim to a tree. We have been extremely unhappy with this prop. I wakeboard, my mom skis, and my dad slaloms. This prop does a horrible job of all of the above. I have read that the High 5 prop is a great prop for water sports behind a I/O boat. Would this be a good choice for us? What are some other options? What pitch would we likely need? I am not sure on the max RPM or prop diameter, but I am taking the boat out tomorrow so I can find out. What other information would help you guys give me a good answer?

My dad is also worried that if we go to a 5-blade 17 pitch prop that it will kill the top end so much that he won't be able to slalom. The current top speed of the boat trimmed up is 45-50 mph depending on water conditions with no skier obviously. When my dad slaloms, the boat will only go about 30 mph. I am under the impression that a torquier prop won't have such a hard time maintaining the speed, but I know very little about prop dynamics.

Here is a picture of the boat, since I know these boats aren't very common.

Thank you in advance!
Chris

 

[Tail_Gunner]

Re: Some prop advice please

Explain your Unhappy with the 4 blade.....and your boat only does 30 with one guy on a salmon ski? elaborate on how many people were in the boat at the time of sking


You should have lost 3-400 rpm with the stainless four blade....was the prop a HR titan if not what make


Just a thought....losing that much rpm or speed towing a skier would indicate a tuneup issue as in timing plugs or wires....maybe a carb clean

 

[nooblet]

Re: Some prop advice please

Explain your Unhappy with the 4 blade.....and your boat only does 30 with one guy on a salmon ski? elaborate on how many people were in the boat at the time of sking

We are unhappy with the 4-blade because we have trouble pulling my dad up on the slalom and it doesn't like to stay up on plane very well. I try to wake board at around 20mph, but just a fraction slower than that and the boat will start coming off plane. My dad is 6'1" and about 230lbs and yes, the boat full throttle trimmed all the way down will only do 30mph, sometimes 32-33 if the water is glass. That is with me driving (130lbs) my mom riding in the passenger seat watching my dad (130lbs) and an ice chest all the way at the front of the boat.

Mostly, the boat just has an extremely difficult time pulling people out of the water without drowning them. I realize this is not a ski boat and I'm not looking for a miracle, just anything that will help improve the situation. The boat does worse when we went from the 3-blade aluminum 19p prop to the 4-blade 19p SS prop.

Chris

Edit: I'm not sure on the make and model of the prop. My dad purchased it used. I don't like buying stuff that I know nothing about, which is why I'm here. I'm tired of these crappy props.

We do regular maintenance on the boat, but I will check to see if the plugs looked fouled.

 

[Tail_Gunner]

Re: Some prop advice please

At this point i do not believe you have a prop issue. A 19 pitch 3 blade should give that boat quite a bit of tourqe. What i am about to suggest is very simple to do but a little intimidating if one has not done this before...But first ask your father the last ime the engine was tuned up...and second on the back of the outdrive there will be a small number stamped on the drive...1.89...2.0...1.98...or 1.50..what is the model yr..

Dont let these question raise concern its hard to trouble shoot over a comp.....and tune ups are extremely simple and there are some easy steps

 

[Tail_Gunner]

Re: Some prop advice please

We are unhappy with the 4-blade because we have trouble pulling my dad up on the slalom and it doesn't like to stay up on plane very well. I try to wake board at around 20mph, but just a fraction slower than that and the boat will start coming off plane. My dad is 6'1" and about 230lbs and yes, the boat full throttle trimmed all the way down will only do 30mph, sometimes 32-33 if the water is glass. That is with me driving (130lbs) my mom riding in the passenger seat watching my dad (130lbs) and an ice chest all the way at the front of the boat.

Mostly, the boat just has an extremely difficult time pulling people out of the water without drowning them. I realize this is not a ski boat and I'm not looking for a miracle, just anything that will help improve the situation. The boat does worse when we went from the 3-blade aluminum 19p prop to the 4-blade 19p SS prop.

Chris

Edit: I'm not sure on the make and model of the prop. My dad purchased it used. I don't like buying stuff that I know nothing about, which is why I'm here. I'm tired of these crappy props.

We do regular maintenance on the boat, but I will check to see if the plugs looked fouled.

Ahh there you go your comfortable with a wrench.....I beleive you have a timing issue...maybe not but the fact that you lose so much power with such a light load and small prop makes it highly suspect...aka the timing is not advanced enough and its very simple to take a read...and if you can do as much....Auto zone will rent you a timing light very cheap

Ok that small of a boat your getting 4 cyl performance....unless you have 1.5 gearing

 

[Robbabob]

Re: Some prop advice please

Sorry to interject TG,

I looked twice for RPM readings (okay, now 3 times), and I don't see any from nooblet.

As TG pointed out, you have seen a 3-400 rpm drop going with the SS 4-blade. That is going to hurt you a lot, both in hole-shot and top end. The 4-blade should already have been a drop to 17P or less.

STILL, need rpm readings from with the 3-blade AL 19 to the 4-blade SS 19, to help confirm this. I don't think you need to go to a 5-blade, but get those readings so we can give input.

Don't worry about the drop in top end, you have to cure the "drowning" out of the hole first. The rest will be easier once you are having fun.

Good luck!

 

[Tail_Gunner]

Re: Some prop advice please

Sorry to interject TG,

I looked twice for RPM readings (okay, now 3 times), and I don't see any from nooblet.

As TG pointed out, you have seen a 3-400 rpm drop going with the SS 4-blade. That is going to hurt you a lot, both in hole-shot and top end. The 4-blade should already have been a drop to 17P or less.

STILL, need rpm readings from with the 3-blade AL 19 to the 4-blade SS 19, to help confirm this. I don't think you need to go to a 5-blade, but get those readings so we can give input.

Don't worry about the drop in top end, you have to cure the "drowning" out of the hole first. The rest will be easier once you are having fun.

Good luck!

"The current top speed of the boat trimmed up is 45-50 mph depending on water conditions with no skier obviously. When my dad slaloms, the boat will only go about 30 mph"

15 to 20 mph loss pulling one skier....on a 4.3 something is amiss

 

[Robbabob]

Re: Some prop advice please

agreed

 

[drivehard]

Re: Some prop advice please

We are unhappy with the 4-blade because we have trouble pulling my dad up on the slalom and it doesn't like to stay up on plane very well. I try to wake board at around 20mph, but just a fraction slower than that and the boat will start coming off plane. My dad is 6'1" and about 230lbs and yes, the boat full throttle trimmed all the way down will only do 30mph, sometimes 32-33 if the water is glass. That is with me driving (130lbs) my mom riding in the passenger seat watching my dad (130lbs) and an ice chest all the way at the front of the boat.

Mostly, the boat just has an extremely difficult time pulling people out of the water without drowning them. I realize this is not a ski boat and I'm not looking for a miracle, just anything that will help improve the situation. The boat does worse when we went from the 3-blade aluminum 19p prop to the 4-blade 19p SS prop.

Chris

Edit: I'm not sure on the make and model of the prop. My dad purchased it used. I don't like buying stuff that I know nothing about, which is why I'm here. I'm tired of these crappy props.

We do regular maintenance on the boat, but I will check to see if the plugs looked fouled.

Perhaps the issue is that you are trimmed DOWN and not UP?
You trim the drive UP for more speed!!!