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McKnight
23-03-2015, 08:52 AM
I am under the impression that the 9hp outboard on my dad's little tinny needs to be raised. I haven't had a chance to have a look at the AV plate while underway yet. It is very sluggish for a small boat, even with only one person.

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I believe the problem is also compounded by being over trimmed, the trim bar however will require some persuasion in order to adjust. You can just tell from the photo how far trimmed in it is.

Noelm
23-03-2015, 08:58 AM
It is a bit hard to say because the photo is not taken level with the bottom, but it sure looks way low.

McKnight
23-03-2015, 09:11 AM
I will try and get some better photos, the boat is a few hours away.

Edit: Is there any particular angles that would so it the best?

The Woo
23-03-2015, 09:29 AM
Ask him to bend down and take pictures from a few angles while his camera is level with the bottom of the boat.
We need to see where the anti-ventilation plate is height wise in relation to the bottom of the boat. The anti-vent plate is where the aftermarket "wings" are bolted to.

aussiebasser
23-03-2015, 09:37 AM
Sorta looks like he might have a long shaft motor on a short shaft hull. Ask him to measure the height of the transom, it will be either 15" or 20". Then measure from the flat at the top of the engine mount to the cav plate on the outboard. That should also be about 15" or 20". I'll guess the transom is 15" and the motor is 20".

McKnight
23-03-2015, 09:45 AM
Sorta looks like he might have a long shaft motor on a short shaft hull. Ask him to measure the height of the transom, it will be either 15" or 20". Then measure from the flat at the top of the engine mount to the cav plate on the outboard. That should also be about 15" or 20". I'll guess the transom is 15" and the motor is 20".

That would seem about right, the clamps for the out board are at the very top of the transom.

Chimo
23-03-2015, 10:00 AM
Hi McKnight

Are you sure the foils are on right way round?

They look backwards to me but maybe its the picture.

If they are backwards that would certainly slow you down

Cheers
Chimo

Dan5
23-03-2015, 10:09 AM
Sorta looks like he might have a long shaft motor on a short shaft hull. Ask him to measure the height of the transom, it will be either 15" or 20". Then measure from the flat at the top of the engine mount to the cav plate on the outboard. That should also be about 15" or 20". I'll guess the transom is 15" and the motor is 20".

I think your on to it there bud............looks like a short shaft hull with a long shaft motor..........No problems if it's raised appropriately.

Dan

aussiebasser
23-03-2015, 11:05 AM
Hi McKnight

Are you sure the foils are on right way round?

They look backwards to me but maybe its the picture.

If they are backwards that would certainly slow you down

Cheers
Chimo

That is the way those foils are designed Chimo. I had a set on my 15. The thing is they should be out of the water when you are on the plane. Those will be about 5" under water on plane, and a 9hp motor will have a lot of trouble pushing them with the prop so deep. The hull will need to have the transom modified, and raised about 5".

Noelm
23-03-2015, 11:06 AM
I will try and get some better photos, the boat is a few hours away.

Edit: Is there any particular angles that would so it the best?
as mentioned, we need a picture with the camera level with the bottom of the hull, showing the cav plate (the things the foil is bolted to)

aussiebasser
23-03-2015, 11:08 AM
That photo does have the camera level with the bottom of the hull.

McKnight
23-03-2015, 11:21 AM
Hi McKnight

Are you sure the foils are on right way round?

They look backwards to me but maybe its the picture.

If they are backwards that would certainly slow you down

Cheers
Chimo

I am fairly certain they are on the right way (up the right way and front to back). The picture is a little deceiving in that they look narrower at the back than the front.

Noelm
23-03-2015, 12:56 PM
That photo does have the camera level with the bottom of the hull.
In that case, the motor is way too deep, probably as mentioned a long shaft on a short shaft transom. It will need to be lifted somehow, either some sort of home made plate or building the transom up (5") the foil running under the water would be a mega drag....and possibly dangerous.

smokin joe
23-03-2015, 04:07 PM
I think Chimo has hit the nail on the head,tabs would cause so much drag facing backwards.have had a few ,never like that and never a problem.I would turn them around and try that before I got carried away with anything major.

aussiebasser
23-03-2015, 05:23 PM
The foils are not on backwards. They have a sharp edge at the front and a squared off edge at the back. The photo clearly shows that there is a long shaft outboard on a short shaft hull. It will be lucky to plane like that. With the prop so deep, the foils on the motor and the massive amount of negative trim, all that setup is safe for is trolling at fast idle. If it gets up to any speed it will try to bury the nose of the boat in the first decent wave you see. Some of the advice you are getting is scary.

Moonlighter
23-03-2015, 06:23 PM
The best thing to do with that set of foils would be to take them off! They will be creating massive drag if they are underwater and doing no good at all.

McKnight
23-03-2015, 10:52 PM
Thanks for the advice, I think lifting it is the likely option. I have the sheet metal guy at work lined up to make a transom extension.

Unfortunately it doesn't get out much so testing a couple of different setups is a pain (easier than getting my project back in the water though, that's a whole other story).

McKnight
26-03-2015, 08:06 AM
Just an update, with some pics and measurements, transom height is currently is 380mm (15in) and to the AV plate is 445mm. So as some of you mentioned it is a long shaft motor on a short shaft transom. Here are some pics. (note it is still at an incorrect trim angle). I believe the motor is a 90 model evinrude 8hp.

http://i.imgur.com/mi83zEm.jpg

http://i.imgur.com/MaotAIe.jpg

http://i.imgur.com/9GYYRSb.jpg

http://i.imgur.com/9qunsOl.jpg

Edit: Any better

ericcs
26-03-2015, 02:20 PM
pics aren't showing up!

McKnight
26-03-2015, 02:52 PM
pics aren't showing up!

Did that fix it?

Chimo
26-03-2015, 03:04 PM
Yes.

Need to lift the motor some 5 inches.

McKnight
26-03-2015, 03:13 PM
Wouldn't 5 inches put the AV plate out of the water? Or does it need to go that high so it just skims the water?

aussiebasser
26-03-2015, 03:59 PM
As I said earlier, short shaft is 15", long shaft is 20". You have to raise the transom 5". You have to do this in such a manner that it is solid enough so that the motor can't twist it. Welding is about the only way.

aussiebasser
26-03-2015, 04:02 PM
Find a bit of stainless threaded rod the same size as the trim holes and pit it right through both sides with a nut on each end to solve the negative trim issue.

The Woo
26-03-2015, 07:02 PM
Yes.

Need to lift the motor some 5 inches.


As I said earlier, short shaft is 15", long shaft is 20". You have to raise the transom 5". You have to do this in such a manner that it is solid enough so that the motor can't twist it. Welding is about the only way.
Lifting it 5 inches will see it far too high.
1" to 1.5" at the most judging by those pics. There is a keel there as well which will cause significant turbulence.
And yes, the trim is tucking the engine in, driving the bow down. Trim it out a hole or two.

gofishin
26-03-2015, 08:57 PM
Lifting it 5 inches will see it far too high.
1" to 1.5" at the most judging by those pics. There is a keel there as well which will cause significant turbulence.
And yes, the trim is tucking the engine in, driving the bow down. Trim it out a hole or two. Woo, pics are deceiving due to significant -ve trim. 1 to 1.5" would not be anywhere near enough, but yes, possibly 5" might be too much (due to the external keel).

McKnight, is that 380 to the very bottom of the external keel extrusion, or top of it (I.e. Bottom sheets)?

You need to temporarily prop the motor so that the A/V plate is parallel to the keel, then measure up from A/V plate to bottom, and top, of keel. The bottom measurement and 1/2 way between these two measurements is a good starting point for a transom extension. If it were my tinny I would also be doing a keel-cut, to get clear water to the prop & the motor as high as possible. Remember, it is easy to go up after an extension (chock etc), but painful ($) to go down!
Cheers
Brendon




Sent from my iPhone using Tapatalk

stevej
26-03-2015, 09:10 PM
sell it and buy the correct shaft length
take those silly foils off, considering they are on backwards as well

boats dont go fast enough for the boat to be sitting on top of the water
it can roll up a inch or two higher the bottom of the boat

Fed
27-03-2015, 06:44 AM
Looking closely at the pictures I think a short shaft could be too high.
Foil is around the right way.

I'd remove the foil & play with the trim before looking at raising the motor.

I have to say when the thread first started the picture fooled me too, at first glance it looks like it was taken from a standing up position & the foil did look backwards.
Aussiebasser was onto it.

Noelm
27-03-2015, 07:26 AM
maybe, just for kicks, lift the motor up as high as you can, looks like you might get an inch or two? remove the foil, fix the trim, and take it for a run, will only take a bit of time, and cost nothing to do, and MIGHT just make it acceptable.

McKnight
27-03-2015, 07:36 AM
Woo, pics are deceiving due to significant -ve trim. 1 to 1.5" would not be anywhere near enough, but yes, possibly 5" might be too much (due to the external keel).

McKnight, is that 380 to the very bottom of the external keel extrusion, or top of it (I.e. Bottom sheets)?

You need to temporarily prop the motor so that the A/V plate is parallel to the keel, then measure up from A/V plate to bottom, and top, of keel. The bottom measurement and 1/2 way between these two measurements is a good starting point for a transom extension. If it were my tinny I would also be doing a keel-cut, to get clear water to the prop & the motor as high as possible. Remember, it is easy to go up after an extension (chock etc), but painful ($) to go down!
Cheers
Brendon




Sent from my iPhone using Tapatalk

The 380mm is practically inline with the bottom of the bung, so no it is not to the external keel.

Yes the negative trim gives the illusion that they are on backwards but they are not. I did try and get him to take some wide angle photos for better perspective.

The plan of attack is next time I am up there we will sort the trim issue out and remove the foils. Then take it out for some testing, get a clearer idea of what is happening at the correct trim.

Then we will start by chocking it up two inches then an inch at a time if it doesn't seem high enough.

aussiebasser
27-03-2015, 09:49 AM
If you chock it up more than 2" you will probably lose that motor off the back. There are only 2 shaft lengths available to you, 15" and 20" that is all that have ever been made for tinnies and small outboards. Yes you can get 25" in big offshore motors. The external keel does not matter. Go to any boat shop and measure a short shaft transom and a long shaft transom. You will find that they are 15" and 20". Raising the transom 2" May help a bit, but it won't be right. Easiest fix would be to sell the old long shaft motor and buy a late model 8 horse. Looking at the prop set-up that is a very old outboard, and would be unlikely to have all 9.9 hp left. Once the motor is set up, those foils are fine, I ran them on my short shaft 15hp Merc on a short shaft Stacer hull with an external keel for years, and they are now on a short shaft Quintrex hull in Victoria still doing the job they were designed to do.

The Woo
27-03-2015, 10:51 AM
Very old tinnies had varying transom heights. This is obviously a very old tinnie. I have also owned very old tinnies, and have had to deal with their idiosyncrasies.

Sometimes a block of wood is needed under the engine mount to lift it up a bit to get the right height. Bit of a bugger on this old boat as the design isn't really allowing for it, so you need to come up with a fix. You might be able to do something with a bit of aluminium box section. Try to retain the lip to stop the engine sliding up and off when (not if) the clamps loosen.

Sure as shit though, if you add 5" to it, you'll need a different engine becasue it will ventilate until the cows come home.

The blokes who have their blinkers on and are insisting it either needs a 15" or 20" engine or transom are just giving you bad info.

McKnight
27-03-2015, 12:08 PM
Chocking it up was just to get the right height before committing to a permanent solution. I got a 2 inch section (2 lots of 25x50 rhs made into 50x50)made up at work for nothing so that's why I am starting there. Once we figure out if we need anymore than that, it will become permanent.

When it gets raised it will also have bolts used to secure it.