tri-hull bounce

[Philster]

Re: tri-hull bounce

Rich, your transducer mounting, which was done incorrectly as you noted: Did this cause porpoising?

Maybe we should pursue the most likely 'big' scenarios and work our way down the list. 80% of porpoising is caused by _______________.

If improper transducer mounting is the answer, I'll retire from these boards immediately.

 

[cyclops2]

Re: tri-hull bounce

Phil

No one should retire if they are sincerely trying to help. The solution is probably not going to be found untill next spring.

We will still respect you.





Untill then.

 

[99yam40]

Re: tri-hull bounce

If you cannot trim down far enough to cause the bow to plow then my thoughts are you need some transom wedges to change the angle of the motor or transfer some of the weight up front.

I bought a used 16' Xpress SV with 40 hp, it had a tail on it,and I removed it.
Took it out on the water and I had to put my brother up on the bow to keep the boat from porpoising even trimmed all the way down/in while up on plane. I started looking for the wedges, but decided to put the tail back on and it runs great and will plow the bow hard if I do not trim the motor up to get the boat trimmed properly.

 

[paul33]

Re: tri-hull bounce

Ok confession time and be easy on me, bought boat without test run. Started it with ears at sellers house. Threw existing prop on first trip,I understand if some of you bow out now

Put new prop on and transducer on and headed out. With motor fully down and under no wake zone throttle bow of bought rides really high, so much that I have to look off side of boat to see where I'm going. Porpoising happens thru whole trim range

Thks .

 

[Philster]

Re: tri-hull bounce

Well, someone needs to look back at the engine when she's on plane and moving at a good clip to see just where the antiventilation plate on the lower unit is at. It should be skimming above the water line, not drowning. If it needs to come up, you will get a fair am't of rear lift. The whole boat might not have less wetted hull, but the angle of attack stern to bow will be better, as the arse of the boat will be lifted when the antiventilation plate is up on the water. This should plant the bow in a sight better position and the antiventilation plate will be able to rest on top of the flowing water.

So... we keep going back to mounting height. And I, again, feel the hull is just different enough to exaggerate the need.

This is something I'd love to hear about when the time comes.

 

[cyclops2]

Re: tri-hull bounce

Paul

When you look at your boat from a distance. Does it seem to have the bow higher up...bow is at a steeper up angle than most other boats ?
When you are pulling away from the docking area. In gear & at idle or a little above idle. No wake zone. Is that when the bow is difficult to see over ?
Can you force the boat to climb out of the bow high angle ? Roughly how much of the engine rpms were needed ?
1/2...3/4... WOT.
How many seconds do you take to get up on the Porposing plane condition ?

Does the boat feel like the the rear end is just too deep into the water ?

I forgive you for buying on a muffler test only. You can do worse things.

What is the exact make , model of the engine ? There should be a tag somewhere, hopefully. Post the make, model & serial # if possible. The motor might be a very heavy one.

Rich

What make , diameter, pitch & number of blades did you buy ? Where & part # of it ?

 

[V153]

Re: tri-hull bounce

Did this cause porpoising? If improper transducer mounting is the answer, I'll retire from these boards immediately

Reckon it might be an issue if'n the boat were really, really small ...

Confirm that the end of the transducer with the wire sticking out of it is on the inside of the boat?

But seriously I'd bet you have a motor height and or prop issue. Assuming the motor is square & plumb on the transom. My 2nd guess would be a honkin' hook in the hull.

 

[lil buggy]

Re: tri-hull bounce

so Paul,
you are getting lots of info here.

2 boats ago i had a 16.6ft marktwain (stepped) trihull.
first thing i did was put a v-4 johnson 115 (sister motor to your evinrude).
it mounted in the same height as yours does(given that its centered)
i mounted my fish pinger on the flat of the first step on the starbord(drivers)side.
i also had a stingray hydrofoil mounted on the cavatation plate

trimed all in drop the hammer when it levels out trim up or out(s l o w l y ) till it dont go no faster!(youl feel it)

by the way that paint looks great
imho that set up is sweet! that thing will scream across the water

so that brings us to your current situation.

i think you are suffering from two things
first a lil bit of air in your prop (hydrofoil is actually keeping them bubbles in your prop)
and secondly

and i've seen it many many times

you are suffering from ohhh sheet
and pulling the throttle back before you get completely on the plane
that setup will shoot you outa the water, keep it pegged for just another second or two
and she will settle down then you can trim up or out and get that kid sized grin
yes that sucker will scoot

after a few of those you will get comfotable with that feeling and can trim up a lil before the hole shot.

soooo if that dont do the trick we can get into the possibility of a spun prop
engine issues or a hooked hull.

also have to add... that hydrofoil may take a mph or 2 off your top speed
but what it will do is keep you up on a plane(once you get there) at much lower speeds(keep it)

sorry if i went too far(back to the basics)
thats what my gut is tellin me
glad to have you aboard
enjoy that sweet ride

 

[lil buggy]

Re: tri-hull bounce

paul,
other thing i am thinking,
when you lost your prop the first time out,
did the engine revv like mad?

 

[99yam40]

Re: tri-hull bounce

My questions on your props are what size and pitch was the prop that you lost,
how did you manage to loose it ,
and did you buy a prop the same size and pitch as the one you lost?

 

[paul33]

Re: tri-hull bounce

Ya when I lost the prop motor did whine out some, it came with an old prop which I found in the bow compartment, maybe I should try that one. Not sure why prop came off it was first time out. Not sure on prop that was on it cuz she's in davey Jones locker

 

[lil buggy]

Re: tri-hull bounce

gotcha on that one,
if you find your prop see if me cell phone is close:facepalm:

in any event you have two props to try,
there should be numbers on them so at the very least you can try those and you will have a better idea of size and pitch if they dont work

 

[lil buggy]

Re: tri-hull bounce

as far as the over rev goes,
how long has it run since the incedent?
notice anything different at idle or rev?

 

[paul33]

Re: tri-hull bounce

Ya I had it out a couple more times since the prop throwing incident and it seem to run fine but it being first boat I really don't have much to compare to. When I got new prop I gave the boat place all the info on boat and they promptly took my money and said try this one, I will get numbers off both props tomorrow . You need a baggy and lifejacket for cellphone .

 

[paul33]

Re: tri-hull bounce

Just one more thing I have a leak in hydraulics of the lift/trim and had to top it up a couple times would that cause trim to move slightly while Driving?

Sorry shouldve mentioned that before maybe?

 

[smokeonthewater]

Re: tri-hull bounce

It possibly could if you have air in the system.... you'll have to turn ur head and look at the engine... see it it's jumping up and down at speed

 

[lil buggy]

Re: tri-hull bounce

Paul,
i assume the engine runs smooth at idle or rev at nuetral?(if it wasn't right you would be askin, what was that noise)

how hard were you pushing the boat when it was doing this? what was your throttle position?
sorry:redface: i seem to remember NOW you were tubing with it, which would mean that you were at least outa the hole.( cant remember nuttin no more:facepalm
how long a run did you make while tring to get the trim right?

all,
i guess the thrust would keep the trim as in as possible,
so if he had bubbles in the system i guess i could see waves etc... jumping the outboard up and down reguardless of actual trim position.
(the first thought i had was that it wasnt possible for the motor to bounce against the thrust of the outboard)not so sure now

to figure out if its the leaky trim causing the issues he can simply put a pin in the manual trim holes and try one at a time right?

 

[paul33]

Re: tri-hull bounce

Hey guys

Thks for all the suggestions, wish I could get it out on the water tomorrow. Got at least 3 Months before that's going to happen.

When I started this thread I guess I was expectin an easy answer but it being my first boat ever I will need to spend more time on water with her. I am looking forward to trying some of the suggestions I got and I appreciate all of them.

Thks Paul

 

[cyclops2]

Re: tri-hull bounce

Normally a air filled hydraulic system like his is now, WILL cause the prop thrust to ram the trim cylinder to the ...IN... positions. Or cause the bouncing of the motor to to be mostly IN. Causing a bow down condition.
I sure hope the stern foam areas are not soaked with TONS of water.
He has a bow up so high he can not see OVER it idleing in gear in a no wake zone. Bad bad sign. Hope he has a above freezing storage area.

 

[smokeonthewater]

Re: tri-hull bounce

Well thus far he hasn't SAID he was idling in the no wake zone and being brand new to boating he MAY not know that no wake zones are NO wake IE idle zones..... I've seen quite a few novice boaters plowing hard through the no wake zone... Any chance this is the case here Paul?

ps Not pointing any fingers here, just diagnosing.