blow out

[Aggressive Machines]

Okay came back from the lake today , Every time i would take off in my tunnel its like it would start to move and then the prop would blow out. What am i doing wrong ??:confused: do i have the motor to high? i had a 14x22 on there today it was a dog wouldnt turn over 5000K rpms 2 weeks ago i was turning 6100K with a 13.75 x 20 yet it still would blow out !! the motor is about 1" above the rear sponsons and yes i have a LWP my water pressure WFO is arpund 7.5psi and i have a new water pump assy . I want the boat to move when i floor it not blow the prop out. HEEEEEEEEEEEELLLLLPPPPPPP

[200VEGAS]

I would chtry the other prop again and or check all you plugs are firing . And what kind of props where they? A 14x22 is actually maybe 2 sizes larger than a 13 3/4x20 cause of the increased diameter and that dia sounds kinda big for a inlne as well.2 sizes(4 " of pitch) should only cause you to lose 600 rpm or so may be 500 in your case but type and style prop means a lot too..... Got pic's,,,,,,,,,,,,

[olmo40]

I think you mean cavitation not blow out ? Try search on here to start and maybe post a pic of the set up .

7.5psi sounds low ,hows the temp ?

A lot performance props will suffer out of the hole ,do you have a GPS speed comparison?

1 inch of pitch usually varies revs 250rpm @

[200VEGAS]

I think one inch is moere like 150, isnt it? I guess it matters what type of prop and how many rpm your turning. My experiance was on 50-55mph 115 evinrude type

[olmo40]

Not sure on the V4s ,With the merc v6s i find 250 as a bench mark ? There is no right or wrong with props they all run different .Trying to find the right one for your boat is the challenge.:thumbsup:

[76baja18ft]

what kind of prop are you trying to run? how much set back do you have?

[Aggressive Machines]

thanks Guys for the feedback........im calling it blow out kinda like with the race car your slicks are bitting then they just blow out go up in smoke..... The prop starts to bite then it like dosent bite so you have to let out of it and try again..........the motor is running on all 6 and running good.. with the 14x22 after i got it going on the GPS i was running 48.7 mph @ 5000 rpms last week with the 13.75x20 she was running 6100 rpms but i didnt have the GPS at that time (but i could tell she was faster) the type of props i have tryed all are flow thru type. i have 6" of setback
Thanks

[Aggressive Machines]

I think you mean cavitation not blow out ? Try search on here to start and maybe post a pic of the set up .

7.5psi sounds low ,hows the temp ?

A lot performance props will suffer out of the hole ,do you have a GPS speed comparison?

1 inch of pitch usually varies revs 250rpm @
prop not biting :confused:

[200VEGAS]

You mean like stock merc asluminum and you mean thru-hub. And do these props have cup and are they new or reconditioned or used with some nicks

[Aggressive Machines]

flow thru............no damage..............props are used ..........and they are Stainless......the 14x22 is a vengance and the 13.75x20 is a precision propeller . the way im looking at this is if the prop is in the water it should bite yet being a rookie at these boats i have a lot to learn:confused: I think im going to cut down the 14x22 to a 13.5x22 :D

[FAST RALLY SPORT]

AT WFO YOU NEED 12 TO 15lbs. OF WATER PRESS. TO BE ON THE SAFE SIDE. BOBBY

[Aggressive Machines]

AT WFO YOU NEED 12 TO 15lbs. OF WATER PRESS. TO BE ON THE SAFE SIDE. BOBBY
I notice you have a tunnel...........Why is mine cavatating at lanch? what causes this it should jump and go........... i need to check my gauge i dont think its correct.

[Water_Dog]

Does the Vengeance have PVS holes? (vent holes)

[Aggressive Machines]

Does the Vengeance have PVS holes? (vent holes)
yes square ones

[imq707s]

Sounds like cavitation.....

Some props act different than other. Over-hub props like choppers, SRX's, and ET's will slip a lot when coming out of the hole, and then finally grab once the boat planes off.

My ET copy will slip and let the motor rev up to about 5000rpms for a few seconds, then start to grab..bring teh rpms down, then hook.

Some do it worse that others....but it sounds like cavitation. Try a difference prop.

[Water_Dog]

My trophy did the same thing when I hammered it. I put the 1/4" inserts in the PVS holes, fixed it's wagon.

[transomstand]

Just stand on the throttle and let it rev until it catches, shouldn't be more than a couple seconds. At the excessive heights we run, virtually all props will have some cavitation at launch, the prop is just too close to the surface not to pull down some air. Some props will "bite" better than others, and a good prop shop can dramatically improve hole shot with modifications.

[Aggressive Machines]

Sounds like cavitation.....

Some props act different than other. Over-hub props like choppers, SRX's, and ET's will slip a lot when coming out of the hole, and then finally grab once the boat planes off.

My ET copy will slip and let the motor rev up to about 5000rpms for a few seconds, then start to grab..bring teh rpms down, then hook.

Some do it worse that others....but it sounds like cavitation. Try a difference prop.
Yea i remember my dad's ole 64' 14' Larson with a 55hp johnson man she would only go 37 mph but man that boat would jump out of the water..... it seemed to be worst with the 14x22 and worked better with the 13.75x20 Im just going to lower the motor 1" and try again next weekend. I know its trial and era i just figed someone that was a prop guru and had a tunnel could give me a lil help.........

[Aggressive Machines]

Just stand on the throttle and let it rev until it catches, shouldn't be more than a couple seconds. At the excessive heights we run, virtually all props will have some cavitation at launch, the prop is just too close to the surface not to pull down some air. Some props will "bite" better than others, and a good prop shop can dramatically improve hole shot with modifications.
Man i tryed that and it sounded like the motor was spinning way to long i didnt want to blow it up:D

[Aggressive Machines]

I noticed that it was throwing water off the prop about 4-5 ft in the air at wot .......i may have the motor to high im going to drop her 1":D

[Jeff_G]

You may want to look at a cleaver type prop. It is a surface piercing prop and is made to run partially out of the water. Also gives you stern lift as opposed to most props wanting to give you bow lift.
What you are experiencing is cavitation, not blowout. You are bringing air from the surface down and around the prop. Also make sure you are trimmed all the way in until you get on plane.
While 7.5# water at WOT is barely adequate I would feel better with around 10 optimum. With an inline you will never see 15. Your water tell tale should be at the top of the block to relieve and steam pocket that may form. Use the plug on the back of the water jacket for the pressure.

[imq707s]

Man i tryed that and it sounded like the motor was spinning way to long i didnt want to blow it up:D

What did the tach say? How many RPM's was it spinning??

[Aggressive Machines]

What did the tach say? How many RPM's was it spinning??
she would jump to 5500 rpms

[Aggressive Machines]

You may want to look at a cleaver type prop. It is a surface piercing prop and is made to run partially out of the water. Also gives you stern lift as opposed to most props wanting to give you bow lift.
What you are experiencing is cavitation, not blowout. You are bringing air from the surface down and around the prop. Also make sure you are trimmed all the way in until you get on plane.
While 7.5# water at WOT is barely adequate I would feel better with around 10 optimum. With an inline you will never see 15. Your water tell tale should be at the top of the block to relieve and steam pocket that may form. Use the plug on the back of the water jacket for the pressure.
Hey Jeff i used the hole that the temp gauge was in its sets between 2 & 3 cylinder . Should i drill and tap a hole in the top? I didnt see one at the top. I was trimed all down at take off.

[76baja18ft]

I love the Omc Shooter props on mine.. I have tried sevearl different props on my boat and i also go back to my shooter.. I run a 27 pitch shooter on mine.. i have also ran a 25 pitch.. and both worked great.. it will jump out of the hole and being a smaller diamater prop it doesnt have alot of bow lift...i have 28 pitch clever i run on it at times ,, but it cavitates like crazy out of the hole until it finally hooks up

[Aggressive Machines]

I love the Omc Shooter props on mine.. I have tried sevearl different props on my boat and i also go back to my shooter.. I run a 27 pitch shooter on mine.. i have also ran a 25 pitch.. and both worked great.. it will jump out of the hole and being a smaller diamater prop it doesnt have alot of bow lift...i have 28 pitch clever i run on it at times ,, but it cavitates like crazy out of the hole until it finally hooks up
is this like a raker prop?

[Carter Powell]

Here is a little trick you might want to try. If you have the square bleed holes in the base of the prop do this. Put some masking tape inside the prop to cover each bleed hole. Now take some clear silicone seal and fill each hole until it is full and smooth. After it is cured try you rig again. This will keep the excess exhaust away from the blades and psssibly let them get more bite. I have done this many times and it has always helped.


Best wishes, Carter Powell

[Aggressive Machines]

Here is a little trick you might want to try. If you have the square bleed holes in the base of the prop do this. Put some masking tape inside the prop to cover each bleed hole. Now take some clear silicone seal and fill each hole until it is full and smooth. After it is cured try you rig again. This will keep the excess exhaust away from the blades and psssibly let them get more bite. I have done this many times and it has always helped.


Best wishes, Carter Powell
Hey that sounds like a plan why do they put the square hole in there any way?
Thanks

[76baja18ft]

is this like a raker prop?

nope... its a 4 blade prop

[Aggressive Machines]

So i had a lil time today (slow @ the shop today) so I took a lil info from Jeff and a lil from Sam and by the way it was a laser II 14x22 prop i was trying so any ho whipped out the 6" cutoff blade and the ole tire balancer and went to whacking ,forming,templet making,balancing and come up with this bad boy instead of a 14x22 its now a 13x22 cleaver flo thru Super Dave Special ! Ill let you guys know if i know what im doing or if i wasted a prop:D She is balanced and im got to the ramp in the morning

[Carter Powell]

The square holes are what they did before the round removable PVS inserts.


Carter Powell

[transomstand]

Wow, that doesn't look too bad, I guess you made a Cleazer:D

[sschefer]

I thought I read that the prop's are vented? I didn't think the Vengance was a vented prop but it might have been done after.

If I understood right and they are both vented then they are doing what the are supposed to do except you seem to be going beyond it and into hyper cavitation. It doesn't matter, you don't seem to need it. Try a non-vented prop.

[Aggressive Machines]

LMAO...........now to see if it works:cheers:

[Aggressive Machines]

I thought I read that the prop's are vented? I didn't think the Vengance was a vented prop but it might have been done after.

If I understood right and they are both vented then they are doing what the are supposed to do except you seem to be going beyond it and into hyper cavitation. It doesn't matter, you don't seem to need it. Try a non-vented prop.
I can see that will have to be the monies pit..........Props :nonod:

[transomstand]

I can see that will have to be the monies pit..........Props :nonod:

Bill Gates could go broke trying props:iagree:

[Aggressive Machines]

Well if i could get my story straight here........just pulled up the # on the LazerII 48-16992 22p and it comes out to be a 13.5x22 and my Precision Propeller the # on it is 1325x20 wich makes it a 13.25x20 so i do know that i need to stay away from 13.5" dia props guess this lil inline likes RPM's cause she ran better with the 13.25x20. I know this thread is getting old Ill start a new one:D Thanks for all the help:cheers:

[Bruce Washburn]

Jeff G. gave you some good advice. He has dealt with alot of inlines.
An over the hub cleaver should work but may be very hard to find. With the boat you are running you may want to try an inline chopper it should have more front end lift and it may be easier to find a 22 pitch version.

If the lower unit has lower water pickups and you are running it really high, the thru hub with that long of a hub will be tough to make it work. Most of the guys with SJ boats would cut the hubs back to the top of the blades to make them run right. The long hubs would lift the ass end of the boat too much. (They were running them high enough to be running on the gear case at speed) .

Which 115 is it? The old version withthe Distributor type ignition or the later version with the igniton that is more like a v-6. The later version is really equivalent to the old 140 which I would think should easily turn over 6000.

[Aggressive Machines]

Jeff G. gave you some good advice. He has dealt with alot of inlines.
An over the hub cleaver should work but may be very hard to find. With the boat you are running you may want to try an inline chopper it should have more front end lift and it may be easier to find a 22 pitch version.

If the lower unit has lower water pickups and you are running it really high, the thru hub with that long of a hub will be tough to make it work. Most of the guys with SJ boats would cut the hubs back to the top of the blades to make them run right. The long hubs would lift the ass end of the boat too much. (They were running them high enough to be running on the gear case at speed) .

Which 115 is it? The old version withthe Distributor type ignition or the later version with the igniton that is more like a v-6. The later version is really equivalent to the old 140 which I would think should easily turn over 6000.1985 with electronic ignition its rated at the prop. did you see the prop i cut? im shooting at if the 13.25x20 was turning 6100 (didnt have a gps at the time so no speed on that one) and the 13.5x22 dropped me to 5000k and on the gps 48.7 :mad: i built this 13x22 cleazer :D and going to check her out hope to get the RPMs back up:thumbsup: just a thought:cheers:

[Water_Dog]

Dude, that rocks, I hope it works great for ya!!

[200VEGAS]

Im wonder what will happen with no cup. Very guttsy move mr aggresive

[gmjim]

Thats creative for sure!!

[pyro]

There's a few points I'd like to add here:

Some props are designed to run fully submerged. Others are meant to run on the surface. Some will do both. Surfacing or semi-surfacing props have key design features that allow them to work. The tips and trailing edges typically have some "cupping" or slight concave "scoop" shape. This helps maintain "bite" during a ventilation condition.

Cleavers get most of their tail-lifting characteristics from the "wedge"-shaped thickness profile of the blade: Thin on the leading edge, THICK and squared-off along the trailing edge. Cutting a round-ear prop down does NOT turn it into a Cleaver or ET. Now, you have a prop with less blade area and less cupping-- NOT typically what you want if you're having trouble with losing bite on holeshot. Also, there is MUCH more to balancing a prop than just weight balance. Each blade needs to have the same pitch. Pitch is often "progressive" across the blade surface, making it difficult to measure and tune without special tools.
I suspect that the modified prop will not perform well, but all these things start out with some experimenting. :) Let us know how it runs.

The revving and slipping is called VENTILATION. The term "Cavitation" refers specifically to the destructive forces caused by small water vapor bubbles forming and collapsing on the low-pressure side of the prop blades or skeg. Cavitation can erode piant, or even metal if the condition is severe enough. Air causes ventilation. Ventilation can cause cavitation, but they are not the same thing. Even so, the terms tend to get thrown around and interchanged. The plate above the prop is called an anti-ventilation plate, but people commonly call it a cav plate. ;)

When you run "up high", even a good surfacing prop will still rev up and slip as it lays down on plane. This is because the prop is coming up the surface, and spinning faster than the leading edge can feed it clean water. It's normal to see 5000 or 6000 RPM for a few seconds until the revs drop and the prop gets bite. Cupped props designed for this purpose have less of the slipping tendency. "Vented" thru-hubs can take advantage of an intentional "controlled" slip condition, thus keeping the motor in its powerband longer.

Most thru-hub outboard props were designed to be run fully submerged. Some stainless props such as the 13.75" diameter Trophy can be run up high and still perform well. Aluminum thru-hubs are useless for this type of application. They will slip badly through the entire range if they're not kept underwater. Ventilation usually causes a massive loss of thrust with these props. Lasers like to be buried underwater, but some boaters have had success running them up higher.

Every aspect of performance on that boat will be out the window until you put a suitable prop on the shaft. Look for a small-hub Trophy or other small-diameter thru-hub, or perhaps a small-ear Chopper. As was mentioned above, a european-style thru-hub cleaver may also work well.

Good luck...

-Chad

[Aggressive Machines]

Im wonder what will happen with no cup. Very guttsy move mr aggresive :thumbsup: I might of wasted a prop but you live and learn and im not setting on the porch:D

[Aggressive Machines]

There's a few points I'd like to add here:

Some props are designed to run fully submerged. Others are meant to run on the surface. Some will do both. Surfacing or semi-surfacing props have key design features that allow them to work. The tips and trailing edges typically have some "cupping" or slight concave "scoop" shape. This helps maintain "bite" during a ventilation condition.

Cleavers get most of their tail-lifting characteristics from the "wedge"-shaped thickness profile of the blade: Thin on the leading edge, THICK and squared-off along the trailing edge. Cutting a round-ear prop down does NOT turn it into a Cleaver or ET. Now, you have a prop with less blade area and less cupping-- NOT typically what you want if you're having trouble with losing bite on holeshot. Also, there is MUCH more to balancing a prop than just weight balance. Each blade needs to have the same pitch. Pitch is often "progressive" across the blade surface, making it difficult to measure and tune without special tools.
I suspect that the modified prop will not perform well, but all these things start out with some experimenting. :) Let us know how it runs.

The revving and slipping is called VENTILATION. The term "Cavitation" refers specifically to the destructive forces caused by small water vapor bubbles forming and collapsing on the low-pressure side of the prop blades or skeg. Cavitation can erode piant, or even metal if the condition is severe enough. Air causes ventilation. Ventilation can cause cavitation, but they are not the same thing. Even so, the terms tend to get thrown around and interchanged. The plate above the prop is called an anti-ventilation plate, but people commonly call it a cav plate. ;)

When you run "up high", even a good surfacing prop will still rev up and slip as it lays down on plane. This is because the prop is coming up the surface, and spinning faster than the leading edge can feed it clean water. It's normal to see 5000 or 6000 RPM for a few seconds until the revs drop and the prop gets bite. Cupped props designed for this purpose have less of the slipping tendency. "Vented" thru-hubs can take advantage of an intentional "controlled" slip condition, thus keeping the motor in its powerband longer.

Most thru-hub outboard props were designed to be run fully submerged. Some stainless props such as the 13.75" diameter Trophy can be run up high and still perform well. Aluminum thru-hubs are useless for this type of application. They will slip badly through the entire range if they're not kept underwater. Ventilation usually causes a massive loss of thrust with these props. Lasers like to be buried underwater, but some boaters have had success running them up higher.

Every aspect of performance on that boat will be out the window until you put a suitable prop on the shaft. Look for a small-hub Trophy or other small-diameter thru-hub, or perhaps a small-ear Chopper. As was mentioned above, a european-style thru-hub cleaver may also work well.

Good luck...

-Chad
Thanks for the input............Thats a 50/50 guess that it will not work:cheers: Im by no way a prop guru but i did not mess with the pitch and i would say your wrong on the balance part . But we will see. I do think you for chiming in on this thread . Because of S&F and all that help me in the past I was able to repair my motor and get it running correctly. and by the way there is a lil cup in the tip's.
Thanks

[Aggressive Machines]

Thats creative for sure!!
:D Thanks

[crazy cajun 2]

i had a few props that would cavitate out the hole until i had them worked on then they bite like hell and dont let go if you know a good prop guy he can fix you up. Ronnie guilbert works all my lake and drag props , super guy. he is in Laffayete you can ship him your prop and tell him what you want and he will take care of it and send it back to you

[Aggressive Machines]

i had a few props that would cavitate out the hole until i had them worked on then they bite like hell and dont let go if you know a good prop guy he can fix you up. Ronnie guilbert works all my lake and drag props , super guy. he is in Laffayete you can ship him your prop and tell him what you want and he will take care of it and send it back to you
Thanks for this info, thats an idea:thumbsup:if you could pm me with his info
Thanks

[pyro]

You can spend all kinds of money "guessing" and paying someone to re-work unsuitable props, or you can try some that are already designed to suit your needs. There are lots of good used props out there for sale. There are many people on this board who have experience with setting up hulls like yours. If you post a new discussion thread titled:
"Prop choices for Carlson Contender with inline?"
...you'll get some knowledgeable replies that will save you a lot of money and headaches.

It's your boat, and your money. I was just trying to help. :cool:

[Aggressive Machines]

You can spend all kinds of money "guessing" and paying someone to re-work unsuitable props, or you can try some that are already designed to suit your needs. There are lots of good used props out there for sale. There are many people on this board who have experience with setting up hulls like yours. If you post a new discussion thread titled:
"Prop choices for Carlson Contender with inline?"
...you'll get some knowledgeable replies that will save you a lot of money and headaches.

It's your boat, and your money. I was just trying to help. :cool:
Thanks you are a lot of help :cheers: lets try it and see im game

[76baja18ft]

If you post a new discussion thread titled:
"Prop choices for Contender with inline?"
...you'll get some knowledgeable replies that will save you a lot of money and headaches.

It's your boat, and your money. I was just trying to help. :cool:...

i dont have an inline on mine.. but a Shooter prop works great on it....

[Aggressive Machines]

...

i dont have an inline on mine.. but a Shooter prop works great on it....
how much set back and how deep u running the motor?:confused:

[76baja18ft]

6 1/2 inches of set back.... and i run a hydraulic jackplate:cheers:

http://i332.photobucket.com/albums/m321/riverrat351/Starbuck/Starbuck005.jpg

[Aggressive Machines]

6 1/2 inches of set back.... and i run a hydraulic jackplate:cheers:

http://i332.photobucket.com/albums/m321/riverrat351/Starbuck/Starbuck005.jpg
o yea the hydrolic plate Sweet what kind of speed you getting with that big burly 200:eek:

[76baja18ft]

low 80's
:D

[Aggressive Machines]

low 80's
:D
nice...........i never noticed at first you got the same boat. dose it handle good at that speed do you stay out of the trim:D ive read they sre blow overs:mad: i havent seen speeds like you have but mine seems to handle good :thumbsup: are these heavy hulls?