Outboards for a catamaran

[Ado]

I have a 38' catamaram with 2 Yamaha 9.9's which are now 14 years old and need replacement. Yamaha no longer manufacture a suitable 9.9 for my application and I'm looking for a suitable alternative. My search has lead me to the Tohatsu MFS9.8ETUL of which I know nothing other than the spec in the brochure. Does anyone have any experience of this outboard and its suitability

 

[alahol2]

Lots of places advertising Yamaha 9.9HP high thrust outboards, What makes them unsuitable?

 

[Ado]

I have currently 2 GEX's which was superceded by the LEX which Yamaha Europe have confirmed is no longer made and I've checked round the dealership looking for old stock without success. The present 9.9 is fitted with an electric hoist which I can't use, it's too heavy, too expensive and wont fit my lift system.

 

[AngusMcDoon]

Lots of places advertising Yamaha 9.9HP high thrust outboards, What makes them unsuitable?

It's probably because the OP wants an extra long leg. Yamaha used to do this, but stopped a while ago now only doing standard and long. This was a disappointment to owners of small multihulls as it was the go to engine for that application.

 

[AngusMcDoon]

My search has lead me to the Tohatsu MFS9.8ETUL of which I know nothing other than the spec in the brochure. Does anyone have any experience of this outboard and its suitability

I had the same problem when I needed to replace my Yamaha 9.9 extra long as the main engine on a Dragonfly 920. The only extra long leg 10 hp engines made now are Honda, Tohatsu and Selva. I bought a Tohatsu - the one you are suggesting. It was fine. I noticed no change in consumption or performance and nothing ever went wrong with it. I had to thin the mounting block on the hull slightly to fit it as the Tohatsu clamps don't open quite as wide as on the Yamaha.

The only point of interest is that you need to change the oil regularly. To keep emissions down the standard oil is a thin specification. When the oil ages and on a hot day it gets really thin and the low oil pressure light can come on intermittently. An oil change solves it. On a cold day the engine is quite steamy from the idle exhaust vent on the leg above the waterline, but Tohatsu informed me that this is normal. All Tohatsu engines are E10 compliant.

If you go with Tohatsu and the exact engine specification you need regarding prop, leg, charging, starting, powered leg lift, remote control etc. is not available on Tohatsu's website then speak to Tohatsu UK. They made mine up to my requirements of options and got it to a dealer within 2 days. They seem friendly and willing to help.

 

[Chiara’s slave]

Further to that very nearly complete post, Honda do the extra long in the 15 hp, which we have on our DF920, with a high thrust prop, should the op think a small power upgrade was useful.

 

[Boathook]

I had the same problem when I needed to replace my Yamaha 9.9 extra long as the main engine on a Dragonfly 920. The only extra long leg 10 hp engines made now are Honda, Tohatsu and Selva. I bought a Tohatsu - the one you are suggesting. It was fine. I noticed no change in consumption or performance and nothing ever went wrong with it. I had to thin the mounting block on the hull slightly to fit it as the Tohatsu clamps don't open quite as wide as on the Yamaha.

The only point of interest is that you need to change the oil regularly. To keep emissions down the standard oil is a thin specification. When the oil ages and on a hot day it gets really thin and the low oil pressure light can come on intermittently. An oil change solves it. On a cold day the engine is quite steamy from the idle exhaust vent on the leg above the waterline, but Tohatsu informed me that this is normal. All Tohatsu engines are E10 compliant.

If you go with Tohatsu and the exact engine specification you need regarding prop, leg, charging, starting, powered leg lift, remote control etc. is not available on Tohatsu's website then speak to Tohatsu UK. They made mine up to my requirements of options and got it to a dealer within 2 days. They seem friendly and willing to help.

Thats interesting to hear about modifying an engine to start with. I may well be looking for a new engine this winter as my Honda 30 may be past economical service / repair. Have found the Honda very good and a very good dealer who seems to care though.

 

[Ado]

Thanks for all the responses. The Honda 15 in long shaft would be a little too heavy or my system which relies on string to lift the engines clear of the water. Angus, how did you find the Tohatsu in reverse, how well did it stop your Dragonfly from say 6knots. I guess the 920 weighs just over 2 tons were my cat is 4.6 tons so would have greater momentum.

 

[AngusMcDoon]

Angus, how did you find the Tohatsu in reverse, how well did it stop your Dragonfly from say 6knots. I guess the 920 weighs just over 2 tons were my cat is 4.6 tons so would have greater momentum.

I don't know from 6 knots as I never motored at that speed. At slower typical marina motoring speeds it was adequate without being stunning. I never bumped into anything because I failed to stop. Yes I had about 2 tonnes, but a single engine, whereas you'll have 2, so not too different per engine.

 

[Chiara’s slave]

The thing that made the difference for us was the prop. The standard prop just cavitated in reverse. Our 15, btw is power trim/tilt, I shudder to imagine the Mrs dealing with a rope lift.

 

[Ado]

I usually sail singlehanded and when I have a crew they are younger and stronger. Lifting has never been an issue due to the system leverage and 8:1 tackle but additional weight could well overstress a a system that has been reliable for 35 years.

 

[Ado]

Angus which prop did you have as I believe Tohatsu offer 3 or 4 blades props and various pitches.

 

[Chiara’s slave]

Angus which prop did you have as I believe Tohatsu offer 3 or 4 blades props and various pitches.

Mine’s an aftermarket one by polastorm. If you’re looking at 6kn under engine, your pitch is going to be as small as anyone makes. 5” is not too little. Tohatsu may offer that kind of thing, or someone else might.

 

[Ado]

Thanks for that. My information is that Tohatsu standard prop is 71/2'' with a alternative of 7''. However I have been told a 4 blade 5'' option is possible which could be suitable.

 

[C08]

I have had a couple of Tohatsu engines fitted from new with Ultra long shaft kits. The first a 30hp 2 stroke I had for 10 years perfect reliability and lots of oompf but a bit noisy, the second a 20 HP 4 stroke that was fine apart from a corroded gearbox bearing carrier after 8 years. It did not fail but replaced as a precaution. The carb fouled up with white calcium like crusty deposits and the dealer was not hopeful that U?S cleaning would clear it so bought a new carb, just out of warranty.Also generally reliable and quiet. I changed that to a 4 blade prop that seemed better ahead and in reverse.
I quite liked the Tohatsus, they are light and efficient but not so heavily built as my current Yamaha 25 high thrust motor.

 

[Chiara’s slave]

Thanks for that. My information is that Tohatsu standard prop is 71/2'' with a alternative of 7''. However I have been told a 4 blade 5'' option is possible which could be suitable.

Tuat is what I have, it works better than any multihull engine/prop setup I have previously had. Large area, zero camber blades.

 

[AngusMcDoon]

Angus which prop did you have as I believe Tohatsu offer 3 or 4 blades props and various pitches.

It was 4 blade and the finest pitch. I can't remember the value and I no longer have the engine or the boat it powered. It was the prop that Tohatsu recommended. Mine didn't have power lift but lifting it by hand wasn't difficult. The Tohatsu 10 hp is lighter than the Yamaha 10 hp so if you managed the latter the former should not be a problem.

 

[Ado]

Thanks everyone, your advice has been a great help.

 

[Neeves]

Have a look at the Seawind website.

Seawind used to make - and may be still do, a 10m cat - Imaginatlvely called a Seawind 1000. It was very popular and they may still make it.

It was powered by 2 x O/B and maybe there is detail on the website of what they use(d). They lifted the O/Bs with a simple block and tackle. They have moved upmarket since and have inboard diesels now in the bigger yachts.

There may be a Seawind Forum, don't know.

Jonathan

 

[thinwater]

Remember that best pitch depends on gearing. I believe the Yamaha's are geared lower.

My PDQ is about 8600 pounds and will motor ~ 7.8 knots. Should be well about 6 knots.

The stopping power of the twin Yamahas compared to the stopping power of a Tahatsu is considerable, IME, since I have had both. Like 40% different. Other that pitch, rpm, and diameter, is the fact that Yamaha props are designed to vent the exhaust away from the prop in reverse, greatly reducing ventilation. This is perhaps the thing that sets the Yamaha motors apart in reverse.

The power tilt IMO was a mistake. That motors are not that heavy and makes fit difficult on many older boats. And then what do you do when it breaks?