Cavitation problems

[Dhadley]

Re: Cavitation problems

BTW - that transducer is not helping either. Think about taking it off for testing.

 

[hwsiii]

Re: Cavitation problems

David, let me tell you that Dhadley is EXCELLENT at this, you need to listen to him.



H

 

[dabood]

Re: Cavitation problems

So your saying just swap the motors? How would that change the height issue, or your saying the heigth issue is not the problem?
I've never heard of that, not saying it would'nt work, just seem weird.
The props would be the same distance from the hull, and the air in the back.

 

[bob johnson]

Re: Cavitation problems

id have to agree with that transducer in a less than idea spot...

you dont want to interfere with clean water getting to the props.

but your height looks fine...

doesnt look like the motors could go out to the side any more than they are now....there is a port in the transom blocking any further movement...

the motors are bolted through...not sitting on the top of the transom, they were probably put there with a lot of thought..

they must have fiberglassed the previous bolt hoels over...cant seem to see where they used to be for the previous single motor set up.,


i bet with learning your trim tabs, and the trim on the outboard and finding the best possible props, you will have a nice seaworthy set up...


the props you have might be worth as much as the props you will end up with..even if you sell them at a discount to someone, or the prop dealer takes them on trade, you wont be out a whole set of prop cash!!!

everything else is patience...you have the boat less than a week...calm down...breathe....trial and error and patience will get your trough this with out much cash outlay...

certainly less than a dual jack plate set up...or a motor bracket!!!( maybe $3000!!)( I was close....http://greatlakesskipper.com/produc...ong-boat-outboard-motor-mounting-bracket.html)

good luck


I am waiting to see how it works out..

bob

 

[dabood]

Re: Cavitation problems

I was told about the transducer, it's where the other one was that came off the boat, however "I will move it", no dought. I was told that by my mech.
Its hard to belive thats the whole problem but I will move in the morning.
Do you think the transducer can affect twins the way this is happing? Its bad is heavy seas, I have to idel speed to keep the warnings from showing (falt trim). On the way back haul *** with the waves. 40 MPH. Its crazy.

 

[dabood]

Re: Cavitation problems

Bob I was told you know your stuff. So I get different props (which one?) use the trim tabs and I'll be good to go? as much as we could guess anyway...
Thats the easy soluation I've heard. Change props and use tabs.....
Is that your final answer???? I do it if you say.

 

[dabood]

Re: Cavitation problems

Bob, should the toe on the motors be in, out, or strait?
Can you give me a pitch? I think I have 21P

Thank you guy so much, David. You'll are great.......

 

[dabood]

Re: Cavitation problems

I mean all you guys. It great to find so much help from people who aren't just tring to mack money.. Thanks....../.

 

[robjen1019]

Re: Cavitation problems

It might help to move the motors as far left and right as you can. That hull has a pretty deep v.

 

[QC]

Re: Cavitation problems

DHadley suggested swapping the lower units to change the propeller direction. You should try that. Also, don't move the transducer, just remove it for testing. Reread your whole thread, start to finish . . .

 

[dabood]

Re: Cavitation problems

what does reread the whole thread mean? I know it might sound stupid, but I don't know. You say swap motors I know that, reread thread, what do you mean?
I'm sorry I just don't know. Brothers, I can catch fish but I was brought up on a boat already rigged and powered.
Just swap motors?

 

[dabood]

Re: Cavitation problems

do you mean read the answers from all? I've had many, I'm just tring to pick what makes the most sence. Which would you pick???

 

[QC]

Re: Cavitation problems

The ones that don't cost any money to try . . .

 

[dabood]

Re: Cavitation problems

I don't what you mean, so I just call some friends and we lift the motors swap them, swap all the cables and steering and try that?
That don't cost money, but Its hard to beleive that will, not saying it won't but the prop and trim seem easier. I don't know what the f..k to do.

 

[bob johnson]

Re: Cavitation problems

well, I know, what i have experienced, and I hope that doesnt get conveyed into knowing any more than what i speak..

I dont know a lot about props, but i am learning...cavitation and prop washout are very dynamic things.

the source can be more than one thing and you really have to take specific controlled steps, to find out what is going wrong...before you can fix it.

many times what we think is going wrong isnt EXACTLY the problem or the WHOLE problem.

now this is all typed pages based on your provided info...if you are slightly off on what you provide, it can skew the suggestions you recieve.

but guys like Hwsiii and Dhadley are certainly more knowledgeable about rigging than i am...I am sure.

I learn fast because it cost money not to learn stuff...

I would set aside a few weekends to try out some remidies offered to you..

I wouldnt PERSONALLY start changing lower units just yet..to me that is further down the road..especially for a new boat owner..

I would personally get the info asked for by a few people and get a baseline set of data so they know whats going on..

flat water, gps verified speed, exact RPMS, postion of trim tabs, and approxiamte motor trim settings...get some pictures of the lower units while at speed so the guys here can see the water flow in and around the lower unit..that is the info that guys need to digest to help you with your problem.


almost impossible to get the one magic answer with out more info...

you cleared up some info with just the photos you provided already.

hang in there..

summer is just getting rolling

bob

 

[QC]

Re: Cavitation problems

dabood,

Swapping the lower units is not swapping the motors . . . Just the portions below the piece of wood in your pictures. So the "motors" stay mounted, the controls stay the same but the parts that determine prop direction are changed. Yes, prop direction can make a difference. There may be a combo that works (or works better) without having to buy anything . . .

Simply removing the transducer and getting it out of the way makes your Fishfinder unusable, but allows you to determine if that helps without actually remounting. Cheaper, faster and you'll know.

 

[bob johnson]

Re: Cavitation problems

this may help understand some of the terminology Dhadley has offered...

it doesnt hurt to learn as much as you can about the basics and then it is easier to render questions and absorb answers...

http://continuouswave.com/whaler/reference/twinEngineMounting.html

bob

 

[Dhadley]

Re: Cavitation problems

Exactly, swap the lower units to reverse the way the props turn. Right now they turn toward the outside of the boat. Swapping the lower will let them turn in towards the center of the hull. Sometimes that lets them pick up cleaner (less aerated) water and reduces cavatation. If it helps, it basically free not counting a little time.

I wouldn't move the motors out much further. Looks like you might run into problems with the hoods hitting.

Yes, I'd simply (temporarily) remove anything in front of the motors that even might remotely create cavatation. Once solved you can start replacing things one at a time.

The toe in (on a V bottom) should be 1/8" to 3/8". Generally that's fine on a boat like this.

 

[dabood]

Re: Cavitation problems

The counter rotation motor is on the port side, I "though" that was correct.
I did move the transducer.
I think I'm going to change props from the 21P Mirage (3) blade to Renegade (4) blade 19P.
Think I should try this before swapping lower units?

 

[bob johnson]

Re: Cavitation problems

are the props loaners? or do you have to actually buy them first??

because the lower unit swap is free , even if it is a little time consuming...

there is a lot of dynamics in twin mounted outboards...

what was the WOT rpms you were getting with the 21P props???

are you only getting cavitation in rough seas?

do you also get it on flat water???? running straight at WOT????

can you easily change over the props someplace once you launch????

or do you have to take the boat out of the water?

if you do go out with the new props, it would be nice to see your numbers
WOT
SPEED
and pictures of the lower unit at WOT!!

good luck

bob