Decisions...

Hey guys i'm not overly happy with my 40hp Merc (3cyl Tohatsu) and i'm considering buying a new 50hp Yamaha. The problem is the 50hp Yammie is a little heavy (so is the Merc). The 50hp Yamaha weighs about 4kg more than the Merc so it's a bit of a problem. <br />Im considering modifying a 30hp Yamaha but I woulden't know where to start and i'm wondering if I can get a good 40hp out of it without loosing much bottom end. Can you recommend any modifications to acheive this?<br />If I buy the 50hp do you think I can shred 5-10 kg off it's weight? Also I would have to modify the 50hp tiller as it's in the middle and too long. The 30hp tiller is perfect. <br />Any recommendations???

Re: Decisions...

What kind of boat are you powering that has created this seemingly impossible weight/power situation, and are we talking two-stroke or four-stroke? There must be a gazillion questions about this on this board and every time the recommendation is the same. It's not practical to modify a small engine to get (in your case) over 33% more power from the 30 HP Yamaha. Nor is it practical to take great amounts of weight off a larger engine to make it the same as a weight as a smaller one. That is unless you have very deep pockets and don't care how much it costs. Then anything is possible but you wont get that job done yourself. A marine "speed shop" would need to be consulted and they aren't cheap.

Re: Decisions...

If you want a wide range of input tell us about what kind of boat you have, how your motor is set-up and what kind of performance you are getting now. Often the problem is there and not a new motor.<br /><br />Baring that my advice is to forget trying to hopup what you have. If you are looking for more power put a used 7ohp on it.

Re: Decisions...

What is happening to cause to you be unhappy with this motor? Is it too slow? Too thirsty? You can't reasonably or reliably increase power or decrease weight on an outboard, so you are left with optimizing setup on the current motor, getting a motor of higher output (50hp will not be much of a noticeable upgrade from 40hp), or finding a much older and lighter motor of the same power (but then reliability comes into question again). I guess if we knew what your setup is and what your end goal is, help would be easier to come by.

Re: Decisions...

Your 40 hp Mercury is a Tohatsu? What country are you in?

Re: Decisions...

Well, what he's not telling you, but was disclosed in another thread is that his boat is only rated for a 25hp outboard.<br /><br />25hp. That says small aluminum boat to me. So, I guess it's not going fast enough for him with that 40 hp on it.<br /><br />He also said he's worried about the law and his over-powered boat. So, he wants 50hp performance from a lightweight 25 hp motor. <br /><br />Never mind....

Re: Decisions...

Riverrat what’s the story? You have to tell all the info not just bits and pieces.

Re: Decisions...

Sorry guys I will give you the full rundown. My current motor the 40hp merc lite is on a heavily reinforced tinnie which is 11 foot long. I'm in Australia and the boat is raited to 25hp but heaps of people go up to 50hp. <br /><br />I've tried a few motors on it cos i'm a bit of a perfectionist. 25hp & 30hp 2 cyl Suziki's which seemed to be bretty good. A 30hp and 40hp 2cyl Tohatsu (not so good) and now my 40hp. Tried a 50hp Yammie but the tiller was too long and being in the centre was a problem. Also had a 40hp Mariner (Yamaha) 2cyl which was great till I sunk it. <br /><br />Basiclly the best weight motor would probably be about 60kg and about 40hp perfect. My current motor is a little heavy and quite rough running. Also the tilt lock mechanism has broken twice (common problem I hear) I get a bit worried when I have so many second hand outboards with no problem yet when I buy new I have dramas. <br /><br />The other problem I now have is the boat is rated for 25hp and the Waterways Authority is now starting to crack down on people with the larger motors. <br /><br />There is a second hand 30hp Yammie for sale i'm concidering buying. I was also considering buying a new 50hp Yammie but as i've already said weight is a problem. <br /><br />Just thought i'd ask your opinion as i'm sick of buying and selling motors. Motor is going to be short shaft tiller steer also.

Re: Decisions...

And for the uninitiated, a 'tinnie' is an aluminium boat.

Re: Decisions...

Are you sure that the Mercury that you have is really a Tohatsu? I've just never heard of anyone complaining about their power to weight ratio before. And that 40 C Tohatsu owned the Sport C race class in the U.S. because it was a rocket compared to anything else in it's size range.

Re: Decisions...

If you want to go fast, I suggest a bigger boat. It would be much safer and keep you out of trouble.

Re: Decisions...

The boat I currently have handles heaps better than any other tinnie and are very sort after for this reason. The Mercury 40hp has a special "lite" model which is a Tohatsu. It does have good power to weight it's just rough and the tilt lock breaking twice is annoying. <br />In sport c did the Tohatsu beat the 3cyl Yammie and Suzuki? What modifications are they allowed?

Re: Decisions...

I'm wonderin a little, the 3-cyl Tohatsu 40hp is a great engine, should not rough run rough at all. Maybe its just in need of a tune-up? <br /><br />My dad had a 40HP short shaft Yamaha, it weighed 67kg without el.start and tiller. It was a great engine, powerful and smooth running. He managed to kill it off putting some crap premix-only oil in the oil tank...

Re: Decisions...

Ivar do you prefer the 40hp Yammie to The Tohatsu? Mine has only done about 12 hrs and was recently given it's 12 hr service so I would have thought it would be in a good state of tune.

Re: Decisions...

Sport C was for un-modified engines. The stock 40 C Tohatsu/Nissan ran a little faster and steered a lot better than the Yamaha, so no one ever ran a Yamaha more than a race or two before they ditched it. Suzuki was too heavy or the CID was too large...No one ever raced one. Also, thanks for the information on your engine. I knew Tohatsu was making a 50 hp for Mercury, but I did not know they were letting them buy the 40 as well.

Re: Decisions...

Hey, I have a tinnie and didn’t know it until now.

Re: Decisions...

riverrat, I'm a yamaha man, so I'd go for the Yamaha. However, my friends that run the Tohatsus are perfectly happy with them. <br />Most notable difference for me would be that the yamaha is maybe a little quieter.

Re: Decisions...

Thanks for the help guys. I nearly got a 30hp Yammie on e-bay Australia but got out bid... Anyway I think I may use my motor a little longer and see if I grow to like it. Internet Outboards in Australia Tohatsu make a 30hp and a 40hp 3cyl for Mercury but I am not aware of a 50hp. I'm talking 2 strokes here. They make a pile of other smaller motors for them also.