Tohatsu 30 hp efi outboard

DIEDOR · 04 February 2023, 19:39

Hello All.
I have excel vanguard xsl485.
I had a reinforced ribbed floor as option fitted. Which I was advised, it would loose a little horse power.
The Boat was new and the Engine was new.
But it never been on the water until 2022.
The Sib is heavier than usual, because I fitted two full length u-channel galvanised steel pieces either side on the floor.
I.E,. Each of the Four aluminium floor plates are bolted together, making the floor like one solid platform
The Sib has also a console with a front bench and 2 swivel seats fitted on the bench
Also, the rear bench has 2 seats fitted on top.
On the front it has a aluminium triangular
Box fitted for Anchor and Rope.
The out board has a propeller guard, and a Hydrofoil ( for Tohatsu) fitted.
The steering is Hydraulic, while the gear shift is cable.
The SIB was designed to carry up to 10 people, but since I fitted the front and back seating arrangement, it is a four seater now
I would have thought, that the engine would do more then 12 knots on Lake Constance, but it did not.
The additional weight I put on the Sib would not come to more then carrying six people.
So, why does this outboard does not more then 12 - 13 knots.
Has anybody got some sugesstios
Thank you All

Blankton · 06 February 2023, 20:09

I would agree it should go faster than that. I think stiffening the floor shouldn't have had a negative effect, it may even be beneficial on such a big boat.

How is the outboard shaft length compared to the transom height?
Whats happening at 12knts. Is the bow lifting really high? Is water spraying up?
Have you got the tubes pumped up to the right pressure?
Did you remember to fold up your launch wheels?

DIEDOR · 07 February 2023, 18:18

Hello Blankton,
Thank you very much for your reply.
The outboard is a short shaft as recommender by the Manufacturer.
It was installed to the right height to the transom, by an Engineer, from the firm I had the Sib from .
The Sib is slightly up at the front, but not too much, because a planing system is installed., So it will not lift the front too much, and there is no spray at all.
The Lifters are made in the USA by Maxi Marine, Model SRB1.
The tubes should be 3.6 psi, and the keel 6 psi.
I only inflate to 2.5 tubes, and 4.5 - 5 psi the keel tube, because the temperature in South Germany Lake Constance, can go between 28 - 38 degrees., And I do not want to risk air expansion.
I have got launching wheels, but I never fitted them, because the Sib was lifted into the water.
Being a new Engine, and Sib, I did run the outboard in, as recommended in the outboard manual.
It was only the last day, during the 14 days over there, that I tried the full throttle., And noticed it only went to 12 - 13 knots
I will in die time check the gear/accelerator cable connections in side the outboard, and I will let you know,
How I got on, and if something was wrong.
The Sib is a EXCEL XHD485 VANGUARD.
I got some pictures I took, but I don't know if I can attach them here.
I will try. Kind Regards DIEDOR

Blankton · 07 February 2023, 19:15

It is really important that you fully inflate your tubes, the boat won't work properly if not at pressure. I appreciate that you are trying to prevent an over-pressure, but under inflated tubes can also damage the boat. I had an aluminium sib (3.1m) which was under inflated and it flexed and bent the aluminium floor! I think this effect could be much worse on your longer excel.

I now always fully inflate the boat. I think that you are quite safe, once on the water the water will keep the tubes cool. I would only let air out if you were pulling the boat out of the water in the bright sunlight. After you have inflated on dry land, you should check the pressure after putting the boat into the water. You may find that the coolness of the water will cause it to loose a bit of pressure and you need to top up the pressure.

This would be my first point to check, before looking for more complex issues such as a broken motor!

Steve509926 · 07 February 2023, 19:44

Quote:

Originally Posted by DIEDOR

Hello Blankton,
Thank you very much for your reply.
The outboard is a short shaft as recommender by the Manufacturer.
It was installed to the right height to the transom, by an Engineer, from the firm I had the Sib from .
The Sib is slightly up at the front, but not too much, because a planing system is installed., So it will not lift the front too much, and there is no spray at all.
The Lifters are made in the USA by Maxi Marine, Model SRB1.
The tubes should be 3.6 psi, and the keel 6 psi.
I only inflate to 2.5 tubes, and 4.5 - 5 psi the keel tube, because the temperature in South Germany Lake Constance, can go between 28 - 38 degrees., And I do not want to risk air expansion.
I have got launching wheels, but I never fitted them, because the Sib was lifted into the water.
Being a new Engine, and Sib, I did run the outboard in, as recommended in the outboard manual.
It was only the last day, during the 14 days over there, that I tried the full throttle., And noticed it only went to 12 - 13 knots
I will in die time check the gear/accelerator cable connections in side the outboard, and I will let you know,
How I got on, and if something was wrong.
The Sib is a EXCEL XHD485 VANGUARD.
I got some pictures I took, but I don't know if I can attach them here.
I will try. Kind Regards DIEDOR

Hi Diedor,

Just for reference, I have an Excel SD360 with a 20hp Merc. 2 adults, 1 dog and kit for the day. Max speed about 28 kph.

I'll take each point as you have in turn.

1. I think you should be achieving around 25 - 30 kph.
2. "it was installed to the right height to the transom, by an Engineer" - An OB can't be installed correctly on dry land and by measurements alone, it takes trail and error.
If you have any packers between the saddle of the OB and the transom I suggest that you remove them and sit the OB directly on the transom and see how that goes.
3. Why are lifters fitted? Didn't the SIB plane before you fitted them? Have you tried the SIB without them?
4. Inflate the tubes to 3.6 psi and the keel to 6 psi and keep topping them up every so often. Your SIB is fitted with a pressure relief valve. That will take care of any over inflation due to heat, and to be honest 38 degrees with the sib sat in water isn't that hot. Having low pressure in the tubes and keel is like trying to push a soft lilo upstream.
5. "Hydrofoil" - by that, do you mean dole fins? If you do, why? Did you try the sib/OB without them? Didn't it plane?
6. "Propeller guard" - it will cause drag and slow you down. Is it particularly rocky where you use your sib?
7. Have you got the correct size/pitch of propeller fitted? What's the WOT RPM of the OB?

Sorry if there appears to be lot of questions. However I do think you need to strip things back a bit to find out why you aren't achieving the speed you want.

chipko · 07 February 2023, 20:22

I too would also have thought it should go better than that, even allowing for the very considerable extra weight you’ve added.

Also agree with comments above re pressure. Always work on the assumption 90% of a sibs performance is found in the last 10% of pressure….slight exaggeration, but you get the drift.

If running at max pressure doesn’t sort it, and fairly confident motor installed at correct height and trim, then look at prop pitch. Need a tachometer (if not got one on your console, a cheapo induction jobbie of eBay will suffice) to check motor achieving correct rev band at WOT….check manual but probably in the region of 5500 to 6000rpm. If revs too low then need to look at a smaller pitch prop. Typically going down each inch will increase revs by approx 200rpm.

Apart from the weight of all this extra kit you’ve installed, one thing I would add, is the hydrofoil will take off a bit of top end speed and the prop guards are notorious for sapping power at all revs.

Hope you get it sorted. [emoji106]

Edit: Steve got there first on most points…need to type faster!

Steve509926 · 07 February 2023, 20:34

Quote:

Originally Posted by chipko

Edit: Steve got there first on most points…need to type faster!

My eldest granddaughter will never belive that comment! Wait until I tell her I can type/text faster than someone else she'll never believe me

Pikey Dave · 07 February 2023, 20:35

First thing, what’s your WOT RPM?
Second thing I would do, is strip out all the additional “stuff” that you’ve added. You’ve just about ticked every box for killing the speed. Start from scratch, get the boat setup correctly & then start adding extras.
As already said, the tubes need to be up to pressure. Otherwise you’re wasting your time.

Fenlander · 07 February 2023, 21:40

I've been looking at this for a couple of days but too busy kitchen fitting then worn out post supper dozing to reply.

However PD has it summed up perfectly "You’ve just about ticked every box for killing the speed. Start from scratch, get the boat setup correctly & then start adding extras"... and Steve has the detail.

Forgive me for overlapping some of your points Steve but here is the list I've had in my head since I first read the post...

The Excel 485 is a heavy beast out of the factory (I'm assuming you mean you've had the extra thick protection outer floor/hull) weighing about that of two Honwave 3.5m alloy floor models and close to three times that of my 3.8m air floor.

Immediately you've added weight by reinforcing the alloy floor with your U-channels. Remember these may stiffen the alloy floor a little but you still have 4.85m of flappy fabric in contact with the water which is power sapping compared to a rigid hull.

Then you have a console with extra seats in the front position which is not only adding weight but may make the outfit bow heavy and reluctant to move freely through the water. You also have a rigid bow locker with anchor so adding to this situation.

Further weight is added in having extra rear seats, steering lines and throttle remotes.

Then we have the prop guard. I've read tests where this will take more than 25% off the top speed. The fins will add to speed reduction just for their drag but if the whole setup isn't properly trimmed with the weight you are carrying they could magnify this situation.

So in truth I'm not that surprised at the low speeds you are getting. Note the RNLI D-class is only 15cm longer than your SIB and also heavy. To get 20kts plus performance 3-up they run 50hp motors.

BTW you mention the design being for up to 10 people. Yes it will still float with 10 people but only at displacement speed with terrible handling so don't use that as a guide.

DIEDOR · 07 February 2023, 22:32

I want to thank you all very kindly, for your advice, and suggestions, and these are all welcome. As you all guessed, I am a novice, and tried to build the Sib up to my liking, without thinking, of the consequences.
Well it looks like I will take all of your advices, and restart when the weather gets better. I know for sure it is not the engine, and the setup. It's the things I put together and added.
I am not too bothered about the low speed, but it will be a problem in costal areas, with the speed the tides travel.
I will go through it again one by one, and eliminate what I have to .

Pikey Dave · 08 February 2023, 09:52

Quote:

Originally Posted by DIEDOR

…but it will be a problem in costal areas
.

I’d assumed from your initial post that the boat was going to be used only on freshwater. If it’s going anywhere near the sea, you need to get rid of the galvanised steel. Galvanised steel + aluminium + NaCl =:Nono:

DIEDOR · 08 February 2023, 19:03

Hello Blankton, Steve 509926, Chipco and Pokey Dave.
Again thank you for your Suggestion, and Advise.
Over the coming weekend, I will open the Boat Shed, and Examen all the points you raised, and I will Report, and will what I have to do
Again, all of your advice and suggestion opened my Eyes, and I am very grateful for that.
DIEDOR

Pikey Dave · 08 February 2023, 21:48

Quote:

Originally Posted by DIEDOR

Hello Blankton, Steve 509926, Chipco and Pokey Dave.
Again thank you for your Suggestion, and Advise.
Over the coming weekend, I will open the Boat Shed, and Examen all the points you raised, and I will Report, and will what I have to do
Again, all of your advice and suggestion opened my Eyes, and I am very grateful for that.
DIEDOR

“Pokey”!! [emoji23]

69cmw · 08 February 2023, 22:28

Quote:

Originally Posted by Pikey Dave

“Pokey”!! [emoji23]

Better than Plumy though [emoji848][emoji23]

Pikey Dave · 09 February 2023, 09:07

Quote:

Originally Posted by 69cmw

Better than Plumy though [emoji848][emoji23]

Much[emoji106][emoji6]

69cmw · 10 February 2023, 21:13

Quote:

Originally Posted by DIEDOR

Hello Blankton, Steve 509926, Chipco and Pokey Dave.
Again thank you for your Suggestion, and Advise.
Over the coming weekend, I will open the Boat Shed, and Examen all the points you raised, and I will Report, and will what I have to do
Again, all of your advice and suggestion opened my Eyes, and I am very grateful for that.
DIEDOR

Post a picture of your outfit before you start stripping it down [emoji4]

Poly · 16 February 2023, 15:50

Quote:

Originally Posted by DIEDOR

Hello All.
I have excel vanguard xsl485.

The out board has a propeller guard, and a Hydrofoil ( for Tohatsu) fitted.

The SIB was designed to carry up to 10 people,

So, why does this outboard does not more then 12 - 13 knots.

Steves step by step thoughts and PD's comments about the excess weight are obviously spot on but there's a point in the OP which I think is worth highlighting: your boat wasn't really designed to carry 10 people. It might have been rated to carry 10 people without sinking / capsizing but the designer almost certainly wasn't expecting 10 to be its normal load. Especially given its only rated for 30HP on a 4.85m boat. My guess is if you ditch the prop guard and hydrofoil you'll see a significant improvement. if 12-13 knots means its actually not even properly on the plane then they will mean its suddenly on the plane and you'll see a marked leap in speed (and fuel efficiency!) from there.