boat porpoising

[longtail]

hi all ,

hoping someone can help me with this . when underway in choppy conditions my boay sits flat and doesn't bounce around much , but in flat glassy calm conditions it tends to start porpoising. i have tried adjusting the trim but that seems to make it worse , any ideas on how to fix this ?
oh and the pin is in the lowest position already

cheers
jason

[FishFinger1977]

Jason,
I had similiar problems with my old savage after trying the trim and tilt settings which did help a bit and rearranging the weight distribution I decided to fit a foil and never looked back, I don't know if they improve top speed and economy like they say as if it did it was negligable but it did however fix the porpoising problem and maybe helped it handle a bit better as it was a light boat to begin with and was thrown around a lot in the chop. Hope this helps. Regards Scott

[familyman]

Jason is your motor at the upper end of the hull range?The other thing is the motor is probably trimmed too far out as planing hulls tend to do this when overpowered and trimmed out too far.Try trimming the motor in until the revs drop off and then trim back out until the revs rise slightly.
cheers jon

[Spaniard_King]

Longtail,

lift the engine up on the transom, mnake sure the cav plate when horizontal with the hull is at least 1/2 inch above the hull. This is the correct engine height. Now tdrive it full trimmed in

Garry

[FNQCairns]

Yep what Garry said [smiley=2thumbsup.gif] if your cav is below, level or only just above lift the engine - makes an awesome overall performance difference and targets the true cause of porpoising directly.

cheers fnq

[slacky]

I have had a similar experience.Try a bit more weight up the front,worked for me.good luck scott

[longtail]

Longtail,

lift the engine up on the transom, mnake sure the cav plate when horizontal with the hull is at least 1/2 inch above the hull. This is the correct engine height. Now tdrive it full trimmed in

Garry

garry ,

does this look right to you?

cheers
jason

[Darryl]

Jason judging by that pic she is raised a fair bit. Mate take a side on pic of the cav plate which is above the prop , we need to see where the cav plate is sitting in conjunction with the bottom of your hull.

Darryl.

[Sportfish_5]

Jason

Post a pic of the bottom of the hull with the engine trimmed down. Thats what we need to see.


Cheers

Greg

[Spaniard_King]

Jason,

you got plenty left if you need it.

as crestcutter says..show us a pic looking from the side of the boat , take it level with the bottom of the boat we need to see the boat and motor
Garry

[James_V17L]

Totally agree with the previous posts...when I first got the Haines it was porpoising on flat water & was real touchy on the trim positioning..thanks
to some sound advice from the good folks on this forum we decided to
drop the engine 2 holes so as the cav plate lined up with the bottom of the hull..thanks again for the pic Hagar...it tranformed the boat instantly.
Cheers,James

[longtail]

like this ?

[Darryl]

Jason looks to me as if the cav plate is way too low , i reckon a good inch too low. I reckon it's your problem.

But wait and see what the other guys reckon jason as i'm no expert but i just had to get my engine raised on the carribean as it was sitting about the same as yours and i had cavitation problems.

[Spaniard_King]

Jason,

toooo low

to lift engine do as follows

place timber under engine skeg, wind jokey wheel so as the engine weight is on the timber
undo top engine bolts and knock them out of there holes in the engine, leaving them in the transom
next undo the bottom bolts about 4mm
adjust jockey wheel so as the correct top holes in the engine align up with the bolts you knocked out.

knock the bolts thru the holes

tighten all 4 engine nuts and bolts

lift the engine off the timber using the jockey wheel

Job finished

should take 10 mins

Now take it for a run and note maximum engine rpm, this will have increased some what.

As you can see its very easy. if you need to adjust it you can repeat the proceedure. because you have an alluminium boat there is no need to seal the holes with silicon although if you wish you can loosen the bolts off when adjusting so you can squeeze some in if need be :)

regards

Garry

[longtail]

alright thanks for your help guys , will do that tomorrow arvo when i get home from work . i'll post a pic when i'm done to check it's right ;)
should have known the dealer wouldn't get it right ::)
bloody tweed marine >:(

cheers
jason

[longtail]

garry ,

think i may have a problem , started the job this arvo following your instructions but as you can see from this pic i think i will have to remove all 4 bolts :-? please tell if i am right
undid top bolts and loosened bottom bolts tried to lift with jockey wheel and would not budge :-?
whats holding the engine on apart from those 4 bolts ??
if i knockk all 4 bolts through will i end up with the donk on the ground ? :o

HELP

cheers
jason 8-)

[Darryl]

Jason , DO NOT knock out the four bolts :o

Gary would have thought the same as me and that is normally the bottom bolts are in a piece that can be slid up or down, but in your case they are just four straight through bolts.

So now the plan is you need something to lift the engine , Then take out the four bolts and i would say go up two holes (Gary might say different so go with what he says.) As i'm only a back yarder.

But you have no other option other than to use a engine lift or block and tackle mate.

[longtail]

thought so ...thanks mate
goes in for it's 20hr service next week might be better off getting them to do it 8-)

cheers
jason

[Spaniard_King]

Crestcutter is right,

Most engines just have a slot on the bottom :-?

You will need an engine lifter to do this, get it done at the next service.

Garry

[longtail]

had the service done yesterday and they said the engine is at correct height , but when trimmed all the way down the prop is not tucked under the keel :-? they say the way to fix this is to install a couple of wedges . does this make sense to you?? they explained it to me and showed me another boat to point out the problem ::)
$47 for the wedges and 1hr labour :-/

cheers
jason

[Spaniard_King]

Jason,

I don't believe the wedges will help you, your engine is to low. If you want to bring it to my house on a weekned I will Lift it for you. If it does not fix it I will put it back. I live at Elanora near Palm Beach

Garry