Ross 780 mk1 outboard replacement

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megawatt
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Ross 780 mk1 outboard replacement

Post by megawatt » Dec 8th, '17, 09:53

I am hoping to put a 9.9hp 4 stroke off the transom of my Ross 780. Has anyone else out three in tsp had such a pleasure? My main concerns are what type of bracket will do the job and how to beef up the transom to take the weight. Engine I have is a Yamaha 9.9hp ultra long leg high thrust electric start with forward controls and it weighs about 45 kgs. Any pictures you have of such would be great. Thank you.Image

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byrdsworth
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Re: Ross 780 mk1 outboard replacement

Post by byrdsworth » Dec 8th, '17, 13:07

maybe get something like this fabricated to suit your boat / motor

http://www.dawnmarine.com/products/stai ... bracket-2/

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byrdsworth
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Re: Ross 780 mk1 outboard replacement

Post by byrdsworth » Dec 8th, '17, 14:00

It's a shame more trailer yachts don't have the ability to mount the outboard on the transom

I have basically the same motor on my careel ... 8hp 4 stroke high thrust (no forward controls or electric start though)
it's a beautifully smooth and quiet motor ... sitting on the transome it's great ... wouldn't like to have it on a bracket ...

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Re: Ross 780 mk1 outboard replacement

Post by INMA » Dec 8th, '17, 16:54

Byrds, its a shame more small yachts do not have outboards in wells like the RL24 but all yachts are compromises.

With that sloped stern and an extra extra long shaft outboard, the Ross might be able to get away with a single straight mount off the flat at the bottom braced at the top and still have the clearance to fully tilt. Its certainly worth checking with a tape measure. The inside fibreglass work would still need to be done to take that weight on the road.
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megawatt
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Re: Ross 780 mk1 outboard replacement

Post by megawatt » Dec 8th, '17, 17:51

[email]Thanks for your very detailed replies, there is a lot of useful information in there. Its a bit of a challenge to get in behind the stern transom area as there is a separate locker almost directly behind the mounting area leaving a gap of about 35mm. The previous outboard was a yammie 8hp 2 stroke.
It appears the previous owner set off some expanding foam to fill the gap between the two skins thus allowing the bracket mounting bolts to be compressed through both layers and tightened inside the locker.
Fortunately I wont need to road trip it as it will only go between the handstand and the ramp so gearing up for extended travel not neccessary, perhaps I should have mentioned that.
I have ordered this bracket already off ebay.

https://m.ebay.com.au/itm/NEW-Outboard- ... mwBanner=1

It hasn't arrived yet so not sure whether or not their claims are accurate.
My thoughts are to make up some 25mm marine ply or teak backing boards prepped with everdure and placed inbetween the bracket and glass outside and sikaflexed and much the same deal on the other side inside the locker and then some nice thick washers pressing up against some poly chopping board spacers.
I think the lockers add a fair amount of strength to the overall structure as they are glassed onto the cockpit seats and walls.
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impulse
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Re: Ross 780 mk1 outboard replacement

Post by impulse » Dec 8th, '17, 19:15

The Ross 780 is designed to carry an outboard on the transom and is most likely suitably reinforced to start with. Check with the manufacturer, he lurks around here from time to time.
Cheers Robin.

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Re: Ross 780 mk1 outboard replacement

Post by zebedee » Dec 8th, '17, 22:03

megawatt wrote:My thoughts are to make up some 25mm marine ply or teak backing boards prepped with everdure and placed inbetween the bracket and glass outside and sikaflexed and much the same deal on the other side inside the locker and then some nice thick washers pressing up against some poly chopping board spacers.
Consider using #16 "tube end discs" (bottom left of the page). They're cheap, stiff, postable (since you're not in Melbourne) and have no corners.
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megawatt
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Re: Ross 780 mk1 outboard replacement

Post by megawatt » Dec 9th, '17, 01:27

zebedee wrote:
megawatt wrote:My thoughts are to make up some 25mm marine ply or teak backing boards prepped with everdure and placed inbetween the bracket and glass outside and sikaflexed and much the same deal on the other side inside the locker and then some nice thick washers pressing up against some poly chopping board spacers.
Consider using #16 "tube end discs" (bottom left of the page). They're cheap, stiff, postable (since you're not in Melbourne) and have no corners.
Yep they look good, surprising whats out there these days.
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Re: Ross 780 mk1 outboard replacement

Post by lloydyboy53 » Dec 9th, '17, 21:50

G'Day Megawatt
I had a Brkt almost identicle to that on my Boomaroo with an 8hp Honda 4stroke hanging off it. I think it weighed a bit over 40kgs. It was a Tenob brand from NZ . I was having trouble leaning over the transom and getting enough purchase to pull it up so I bought another set of springs and mounted them on the outside of the bkt, needed longer bolts but it made raising that heavy little sucker really easy.
Cheers john
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Re: Ross 780 mk1 outboard replacement

Post by INMA » Dec 9th, '17, 22:37

That bracket looks like poorly made rubbish.

The mounting plates to the stern look flimsy without sufficient area to transfer the moment forces onto the stern. Compare it to the American brackets and the difference design, manufacture and quality should be obvious.

https://www.ebay.com.au/itm/Garelick-71 ... Sw-vlVjuJ8

Your description of the current bolts through the stern, through foam and through the locker is a soft structure not capable of clamping as a structural member. The instability as its crushed by the bolts means it will never be reliable as a structure.

Trying to clamp that flimsy bracket onto a wooden backing plate on the stern will quickly crush and damage the wood where the bracket compresses the wood. The pressure will quickly damage the wood where the stainless bracket works on the wood.

I can't see how your suggested bracket bolted through the stern, foam and locker will survive the forces of the outboard you are planning to use.
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Re: Ross 780 mk1 outboard replacement

Post by INMA » Dec 10th, '17, 12:08

A bracket like this will do the job on the stern.

http://www.ebay.com.au/itm/2-stroke-Sta ... 0005.m1851

As for clamping through the foam and into the locker, that still sucks.

After positioning the bracket on the transom, drill the holes through to the locker to give a final position.

Then cut the back of the locker out to clear access to the inner stern and clearance for the bolts.

Decide whether the stern is strong enough or not looking at the thickness etc.

If the stern is strong enough, clean it up and bolt with metal backing plates to mount the bracket. Extra bolts at the top and bottom might be good insurance. You might glass the cutout to clean up the area.

If you want more support for the stern, and you believe the locker is strong enough, consider glassing the cutout in the locker to the inside of the stern with flow coat finish. That will extend the support available when you bolt the bracket on. Plenty of glass is good and glass back into the locker to get all the support you can spread forward to take advantage of the locker as much as practical.

I'm thinking the glass thickness on the inside of the stern needs to be about 3 mm with 4 mm of glass back to the locker then tapper the thickness down once your in the locker spreading the structure forward.

While planning all this, think bout the holes going through for fuel electrics and shifters.

On some engines where the shifter quadrant is close to the tilting outboard, its common to run the morse cables around the back of the outboard and onto the lever from behind (the morse kits have these fittings. That allows the outboard to tilt without bending the cablesat the terminations.

The quadrant can be installed to push or pull, its just a different set of holes when you assemble it.

Buy new morse cables when you do the installation. Set it up with old cables till you figure the lengths out then buy new cables of the length needed. New cables will last a long time. Old cables will be hard to adjust and quickly fail due to old wear inside the cables accelerating damage due to the new bends.

You might consider putting a small motorcycle battery as a starting battery in the locker, it will save a lot on wiring. There are good sealed batteries on eBay that couldbe safely installed in a box in the locker.

Those big metal washers look good.

Don't use wood it makes a soft joint that will fail.
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Gezza
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Re: Ross 780 mk1 outboard replacement

Post by Gezza » Dec 10th, '17, 12:48

The bracket seems indeed a bit light to hang 45 kg on it plus forces when motoring.
How about fitting spacer bushes and large diameter washers between the stern and the locker wall (stern, washer, bush, washer, locker, washer) it might be a bit of a fiddle but prevents the crush.
You could cut the bushes to size from some thick walled tubing.
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megawatt
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Re: Ross 780 mk1 outboard replacement

Post by megawatt » Dec 10th, '17, 22:33

lloydyboy53 wrote:G'Day Megawatt
I had a Brkt almost identicle to that on my Boomaroo with an 8hp Honda 4stroke hanging off it. I think it weighed a bit over 40kgs. It was a Tenob brand from NZ . I was having trouble leaning over the transom and getting enough purchase to pull it up so I bought another set of springs and mounted them on the outside of the bkt, needed longer bolts but it made raising that heavy little sucker really easy.
Cheers john
Yes the "Tenob" brand look good, Whitworths have one for about $500, thought i'd take a punt on the bracket quoted above still on its way, so still unsighted. But yeah the more I think about it, the more its starts to worry me.
Hazard a guess, I will be spending a few days grinding and glassing at the very least.
Got a fair bit of experience at it so no problem.
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Re: Ross 780 mk1 outboard replacement

Post by megawatt » Dec 11th, '17, 00:38

Update....
Did the rounds and came up with this..

https://www.ebay.co.uk/itm/Stainless-St ... 2314181872

Looks strikingly similar.

(go to page 51) https://www.lalizas.com/filemanager/upl ... 014_EN.pdf

If its a genuine Lalizas unit then I would be confident in the weight claim. I will do the magnet test to see if its 304 or 316.

Just a bit of glassing up ahead.

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Re: Ross 780 mk1 outboard replacement

Post by INMA » Dec 11th, '17, 07:16

What was wrong with the one I suggested?

http://www.ebay.com.au/itm/2-stroke-Sta ... 0005.m1851

The pressings are high quality and its less money here than the English bracket.

The plastic pad should not be an issue with the American mold because they use high quality UV Resistant plastics. The Chinese plastic pads are a problem.
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Re: Ross 780 mk1 outboard replacement

Post by megawatt » Dec 11th, '17, 16:59

INMA wrote:What was wrong with the one I suggested?

http://www.ebay.com.au/itm/2-stroke-Sta ... 0005.m1851

The pressings are high quality and its less money here than the English bracket.

The plastic pad should not be an issue with the American mold because they use high quality UV Resistant plastics. The Chinese plastic pads are a problem.
Nothing wrong with it at all, its just I already have one ordered from an Australian seller which has yet to arrive (by tomorrow hopefully) and was trying to get more info on it which sadly the aussie guy doesn't provide.

The one you mentioned certainly looks the goods good ol' USA quality
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Re: Ross 780 mk1 outboard replacement

Post by AZAmagnum » Dec 11th, '17, 20:44

I know you already have the motor, but I'd seriously consider getting a 2 stroke with high thrust prop.
Youll save yourself about 20kg, back problems, and transom problems.
If our Honda 10 dies, then a tohatsu 2 stroke might be the replacement.

How do you like the Ross so far ?

Aaron
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megawatt
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Re: Ross 780 mk1 outboard replacement

Post by megawatt » Dec 18th, '17, 21:36

AZAmagnum wrote:I know you already have the motor, but I'd seriously consider getting a 2 stroke with high thrust prop.
Youll save yourself about 20kg, back problems, and transom problems.
If our Honda 10 dies, then a tohatsu 2 stroke might be the replacement.

How do you like the Ross so far ?

Aaron
Hi Aaron tbh havent had her out yet others at the club she came from raved about her
I had a double knee replacement in august so in recovery from that almost good to go
Meanwhile I have been working away improving this and that more to catch up on a lot of outstanding maintenance and to make it more family friendly
Back on topic I had looked into 2 strokes but 9.9 which is the same weight as the eight only comes as a short shaft and then you have start buying this and that to get it to a remote start setup
I am almost ready for sea trials perhaps boxing day
Will update this post and show how I mounted the 4 stroke and strengthened the transom.
Cheers
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Re: Ross 780 mk1 outboard replacement

Post by AZAmagnum » Dec 18th, '17, 21:50

I'm sure you'll do a proper job Terry.
I think you'll like the "excitement" of the ross.
Keep us updated.
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Re: Ross 780 mk1 outboard replacement

Post by Tinggu » Dec 19th, '17, 09:02

When I was searching for a replacement bracket for Isabella Jane I was bamboozled why nearly all the brackets were for 2 strokes - specifically. We ended up getting one that was rated for a much bigger HP 2 stroke than our Honda and it has been satisfactory, although I beefed it up with extra springs. The local Honda place suggested it was because of the higher torque of 4 strokes...... 2 stroke HP and 4 stroke HP are not the same. Horse power ain't horsepower? ..........I would have thought that there must be some formula which would rate a beefy 2 stroke bracket for a heavier, smaller HP 4 stroke. For example the Mr Boats up to 20 HP or 55kg (one would have thought just right for a Honda BF8) specifically says not for use with 4 strokes - even tiny ones. I would expect the stresses of a 20HP 2 stroke would would be way greater than for an 8HP 4 stroke. 4 stroke brackets seem to start at $400 suiting 7.5 to 30 HP. That's one helluva range, and from USA with the usual ridiculous postage fees. What is the mystery of 4 strokes?
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Re: Ross 780 mk1 outboard replacement

Post by INMA » Dec 19th, '17, 12:54

Tinggu, power is power regardless of the type of engine.

The labeling of brackets as suitable for two stroke or four stroke puzzles me, I thought weight and power were the issues.

However a single cylinder two stroke at 5000 rpm has 5000 power strokes compared with 2500 power strokes for a four stroke engine.

My guess is in America where two strokes have been banned for a long time, the bracket manufacturers use the labeling for two or four stroke to mean new or old.

Remember a lot of old small two strokes were two cylinder and vibration was never an issue whereas now they are all 4 stroke and vibration could be an issue.

As mentioned, I can't see a lot of difference between two and four stroke brackets, perhaps they made the sheet thicker.

Shop around in America an good brackets can be found at reasonable prices.

http://www.ebay.com.au/itm/2-stroke-Sta ... 0005.m1851
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Re: Ross 780 mk1 outboard replacement

Post by Harb » Dec 22nd, '17, 18:29

megawatt wrote: Engine I have is a Yamaha 9.9hp ultra long leg high thrust electric start with forward controls and it weighs about 45 kgs.
Wow, that's almost the same as the latest fuel injected Tohy 20HP. Beefing the transom should be relatively easy, just epoxy a piece of plywood on the outside and the same on the inside or if space is an issue a couple of lengths of fully sealed 20mm thick 3-4" wide hardwood epoxied as backing boards and your transom should be able to handle 50hp easily.
The issue is the crappy folding brackets available, on the stinkboat I had a "heavy duty" auxiliary bracket supposedly made to handle up outboards up to 20HP but was barely able to handle the occasional use of the 29kg 5HP Tohy I had on it. If you can get away with a fixed bracket then you could make one to suit the outboard and use existing holes to save drilling new holes in the transom. You can get some ideas from here,

http://www.nauticexpo.com/boat-manufact ... 45061.html

http://continuouswave.com/whaler/refere ... ckets.html

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megawatt
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Re: Ross 780 mk1 outboard replacement

Post by megawatt » Dec 30th, '17, 12:38

For those interested I have posted a video of my progress on youtube heres the link
https://youtu.be/Oce8PWaPRC4
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Re: Ross 780 mk1 outboard replacement

Post by ralasa » Jan 22nd, '18, 00:43

Hello megawatt, good video,how are you finding the new motor? , I just picked a second hand one, 9.9 4stroke yamaha, wow what heavy beast,
i take it yours stays on the boat permanently, how does it go on the road , Im thinking of making some sort of a bracket to support it, while driving.
can't waiting to see how it goes on the water, cheers Pete

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Re: Ross 780 mk1 outboard replacement

Post by megawatt » Jan 25th, '18, 02:01

ralasa wrote:Hello megawatt, good video,how are you finding the new motor? , I just picked a second hand one, 9.9 4stroke yamaha, wow what heavy beast,
i take it yours stays on the boat permanently, how does it go on the road , Im thinking of making some sort of a bracket to support it, while driving.
can't waiting to see how it goes on the water, cheers Pete
Fantastic motor, bloody reliable but take time to warm it up first. The sea trials went well and the bracket and mounting is working very well.
Only thing I might do is add two plates/ straps to slip over the motor pivot tube coming back to the top bolts on the transom, in effect, a brace at the motoring position.
Im not trailering mine so but I think something like that would also help take the weight and soft suspension on the trailer too.
Next time I go out I will capture some video of it in action for anyone interested.
Thanks btw for your positive comment,
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