Tohatsu 9.8 2S newbie

[Steve509926]

Originally Posted by Fenlander

I was interested you suffered splash and needed packers though... do you get that at all with your Mercury and is that direct onto the transom?

Hi Fenlander, no I don't get any splash back over the transom with the Merc 20efi.

It may be that I won't need any packers when I test the 9.8 with the 7.5 two up and the dog.
I know when I first fitted the Merc one up, it was better with a 10mm packer but it didn't need it 2 up with the dog.

[Steve509926]

Is it normal for a very small amount of what I presume to be gear oil to come out of this hole?

[Fenlander]

Gear oil loss from anywhere not acceptable and not at all likely. Probably 2-stroke oil from the exhaust.

[Steve509926]

Would it come out of that small hole?

[Fenlander]

Just looked at mine and nothing like that visible. In the pic I put a cotton bud into the hole and it just cleaned off the lightest of deposits. A cocktail stick poked right in then barely showed any trace.

I wonder, wasn't your motor used on a yacht and locker stored. Also lowish hours. Could it be a large proportion of its run time has been on 25:1 running in, and when it's been stored it's lay horizontal so never had a chance to drain off after use. So you could be flushing out a build up of oily exhaust deposits possibly? You might get an idea when you drop the gearbox to do the impeller.

[Steve509926]

That sounds very plausible, I'll keep my eye on it.
Thanks David

[Steve509926]

Think I've figured out the probable cause.

I transported the OB yesterday with the Dole fins still fitted, didn't take them off as it started to rain heavy. As I couldn't put it on its side I lay the OB down on its back. After reading the online Owners Manual, I now realise it should only be lay down horizontally tiller side down.
Do you think this could be the cause?

[Fenlander]

Possibly. It just happens that it suits my pack to have the OB on its side tiller side down, powerhead raised a few inches. I wouldn't worry just keep using but you will find out loads when you drop the gearbox and see if there are any historical areas of congealed oil.

[Tommy c]

Originally Posted by Steve509926

Think I've figured out the probable cause.

I transported the OB yesterday with the Dole fins still fitted, didn't take them off as it started to rain heavy. As I couldn't put it on its side I lay the OB down on its back. After reading the online Owners Manual, I now realise it should only be lay down horizontally tiller side down.
Do you think this could be the cause?

Never heard of a 2t having to be laid down a certain way?
Have you checked your gearbox oil Steve or is that hole above the gearbox?

[Steve509926]

Originally Posted by Tommy c

Never heard of a 2t having to be laid down a certain way?
Have you checked your gearbox oil Steve or is that hole above the gearbox?

That's what I thought Tommy, but it's there in black & white in the owners manual, tiller side down, slightly raised.

I'll be checking everything when I service it, but I'm convinced it was because I had it lay down on its back prop slightly raised because of the stupid bloody Dole fins.

[Steve509926]

Hi Tommy, hoping to get out next week to test the 9.8 with a 7.5 prop.
Is Windermere south of Bowness and on the West side relatively quiet so I can do some WOT tests? If not, it's back up to Ullswater.

[Max...]

Main thing (with a 2S) is to keep the power head well above the prop to keep water where it belongs. Having the tiller down helps this a little but I always raise the head up with old cushions/other gear to be certain.

Re’ oil I always go 75:1 to split between commercial 100:1 and leisure 50:1.

[Steve509926]

Screen pic of the 9.8 owners manual showing tiller side down.

Max, when you say you go 75:1 oil, is that on a 9.8? I assume it runs ok?

Does anyone else run at 75:1?

[willk]

The previous owner of mine ran 100:1 and there were no apparent issues caused. I ran 50:1. I think if you are running mid revs then it should be OK, Max... may be onto something at 75:1

I doubt anyone will make guarantees about 100:1 but it is a Thing

[Max...]

It might be my memory going but I think it Fen' who put the idea (75:1) forward many years ago?

I had a Twatsoo 9.8 many years ago but I've been on the Merc 15 for maybe 10 yrs now at 75:1 or therabouts...

I have a load of used mini kids type 'pop' bottles pre-filled with 2S oil that are about 270/280ml to the brim so I just pop one of those in every 20 litres and that is a little richer than 75:1 so it might have been I worked on 70:1 or whatever??

[Max...]

I had a little laminated card I used to carry about in the boat spares box with approximated numbers:

75:1 (1 litre needs 14ml oil)

5 litres needs 70 ml
10 ……..…… 135 ml
15 ……..…… 200 ml
20 ……..…… 270 ml
25 ……..…… 340 ml

50:1 (1 litre needs 20ml oil)

5 litres needs 100 ml
10 ……..…… 200 ml
15 ……..…… 300 ml
20 ……..…… 400 ml
25 ……..…… 500 ml

75:1 (1 litre needs 14ml oil)

5 litres needs 70 ml
10 ……..…… 135 ml
15 ……..…… 200 ml
20 ……..…… 270 ml
25 ……..…… 340 ml

50:1 (1 litre needs 20ml oil)

5 litres needs 100 ml
10 ……..…… 200 ml
15 ……..…… 300 ml
20 ……..…… 400 ml
25 ……..…… 500 ml

BIGGER!

75:1 (1 litre needs 14ml oil)

50 litres needs 0.7L
100 ……..…… 1.4L
150 ……..…… 2.1L
200 ……..…… 2.8L
250 ……..…… 3.5L

50:1 (1 litre needs 20ml oil)

50 litres needs 1L
100 ……..…… 2L
150 ……..…… 3L
200 ……..…… 4L
250 ……..…… 5L

[Fenlander]

I’m pretty sure the discussions to use 100:1 or not have all been about the Yamaha and Mercury/Mariner 15s. I have run both our 9.8 Tohatsu models on 50:1 per the manual that came with them. But yes for the 15hp models specd to 100:1 I use around 75-80:1.

[chipko]

We run our Yam 15 on 50:1 and seems quite happy with no fouling/excess smoke.
Only reason being ease of use as we alternate between Tohatsu 9.8 and Yamahaha 15 which both run 50:1 and can use one pre mix fuel tank for all three.

[smallribber]

I have a few small 2 strokes and for ease of Petrol management I use 50:1 ish on everything. All seems happy on this

[Fenlander]

50:1 is indeed the easy and safe default option. The only thing I have noticed with both Yamaha 15s is their pickup from idle seems a little cleaner on 80:1. But it's marginal.