another prop question... 4 blade help me?

[jbanderson]

Ok I have mounted a 150 marinier 2.5 efi inplace of my blow 75hp mariner.
I cannot get a good bite on the prop, I tried the best thing I could find at the marina witch was a 3 blade 17pitch solas 14.8" diameter.. It hooked as long as I had the trim all the way down witch is not good at all. As soon as I tried to pull the boat out of the water with the trim it would vent the prop.
So.. It seems to me from what ive been reading that pontoons are bad about venting the prop, so wouldnt a 4 blade be best as long as you had extra power to turn it? (witch I have planty of)
I need to get this thing hooking up!! Please help!!
thanks

 

[bobkyle2]

Re: another prop question... 4 blade help me?

i know next to nothing about props... but i have a 150hp mercury... and i have a 21p prop thats been worked on.... so you might try a 21p... thats what ive seen alot on 150hp mercs... im currently looking for a 22p to get some more speed out of... but like i said i know nothing about props ... hopefully someone will come in here and help you out better

 

[steelespike]

Re: another prop question... 4 blade help me?

Yes a 4 blade prop should help; note their diameter and stick with a larger diameter.
You don't need extra power to turn a 4 blade it just needs to be the right size.
What year motor? Tell us about the pontoon.Depending on the size the a 17 may be too much prop.

 

[jbanderson]

Re: another prop question... 4 blade help me?

its a 96 150 2.5 efi 20" shaft
Boat is a 89 fisher 24ft

I gotta get this thing to pull up out of the water, i just dont understand why the 75 that was on it would lift the bow but with the 150 the prop wont grab enough to lift the bow.

 

[steelespike]

Re: another prop question... 4 blade help me?

Can you lower the motor more.And again the 4 blade should help.
Look for a large diameter.
There is a lot of turbulance with a pontoon and usually can't trim too much.
It pretty obvious the faster the boat the more turbulance and probably in a different place.Is the boat rated for a 150?What diameter are the tubes?Have you tried trimming just enough to relieve downward pressure on the bow?

 

[jbanderson]

Re: another prop question... 4 blade help me?

Can you lower the motor more.And again the 4 blade should help.
Look for a large diameter.
There is a lot of turbulance with a pontoon and usually can't trim too much.
It pretty obvious the faster the boat the more turbulance and probably in a different place.Is the boat rated for a 150?What diameter are the tubes?Have you tried trimming just enough to relieve downward pressure on the bow?

Not sure on diameter of the logs, its a fisher 24ft 1989
When im going really really slow, probly 1/8th throttle and about 10mph i can trim just a little and keep the nose from diving down and makeing it shove water/hard to steer but any faster than that and it will blow out with the slightest trim. Also when im going slow with the trim up at all if I turn it would blow out just like if I try to trim it more or speed up.
Also its only rated for a 115hp

 

[steelespike]

Re: another prop question... 4 blade help me?

As you probably realize a 2 tube pontoon is not intended to plane.And I don't know if enough power will truely "plane"it.Is there any distortion in the bottom of the tubes, Are they clean?A toon is technically a displacement boat running most efficiently at about 6 or 8 mph.Obviously we routinely push them past that speed.It can create lots of problems.If a toon mkes 20 mph with 70 hp it would do about 30 with 150.
About 10 mph for double the hp.and double the fuel use.

 

[jbanderson]

Re: another prop question... 4 blade help me?

As you probably realize a 2 tube pontoon is not intended to plane.And I don't know if enough power will truely "plane"it.Is there any distortion in the bottom of the tubes, Are they clean?A toon is technically a displacement boat running most efficiently at about 6 or 8 mph.Obviously we routinely push them past that speed.It can create lots of problems.If a toon mkes 20 mph with 70 hp it would do about 30 with 150.
About 10 mph for double the hp.and double the fuel use.

20mph would be a dream right now! lol

 

[Tail_Gunner]

Re: another prop question... 4 blade help me?

Ok I have mounted a 150 marinier 2.5 efi inplace of my blow 75hp mariner.
I cannot get a good bite on the prop, I tried the best thing I could find at the marina witch was a 3 blade 17pitch solas 14.8" diameter.. It hooked as long as I had the trim all the way down witch is not good at all. As soon as I tried to pull the boat out of the water with the trim it would vent the prop.
So.. It seems to me from what ive been reading that pontoons are bad about venting the prop, so wouldnt a 4 blade be best as long as you had extra power to turn it? (witch I have planty of)
I need to get this thing hooking up!! Please help!!
thanks

Spike:
"Can you lower the motor more." And again the 4 blade should help.
Look for a large diameter.
There is a lot of turbulance with a pontoon and usually can't trim too much.
It pretty obvious the faster the boat the more turbulance and probably in a different place.Is the boat rated for a 150?What diameter are the tubes?Have you tried trimming just enough to relieve downward pressure on the bow?


Take the motor down a inch at a time...Its a pain but your to high. Boats have a Luxury of a transom its easy to put the cav plate a inch or so below the hull and tune from there...Toons have no transom....your tubes are disturbing the water funneling it back to the prop ...You need to find a spot deep enough where the prop will hook up...If there is one......Make sure your tubes DO NOT have water in them...Or worse yet water soaked foam

As to props a big eared pusher not a raked 4 blade