15HP 2stroke yamaha vs 20hp 4stroke tohatsu

[boater1234]

I put my outboard on craigslist yesterday which is a brand new 15hp 2stroke yamaha for $2400.I have a guy who may want to come look at it and buy it.I was thinking of getting a 20hp 4stroke tohatsu in place of it.I have a 200lb 14ft alumacraft that is 63inches wide.My question is am i better off staying with the 15hp 2stroke or will the 20hp tohatsu be the better deal.I know the tohatsu is 35lbs heavier but i like the idea of a cleaner outboard and i will gain the extra 5hp that i think i need.I can get the tohatsu online for around $2400 free shiping and tax included.

I guess my question is will the tohatsu perform as well if i do this because i don't think i will ever see another new 15hp 2stroke again for sale at least that is for a reasonable price anymore as the dealers are slowly jacking the prices through the roof.So i want to make sure before i sell it i am doing right.Will the tohatsu give me just as good overall performance i guess is what i want to know.I'm sure the hole shot will lack a little but the top end shoud be a hair better i would think.I have watched tons of videos on you tube and it seems like the tohatsu has some great power for a 4stroke.Any help would be great.

 

[nwcove]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

id be looking at long term reliability, and parts availability. (my thought would be to stay with the yamaha..... just my opinion.)

 

[boater1234]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

As far as realiability the tohatsu is up there with the best of them as they make nissans and mercs up to 30hp.That was never an issue i have as i think tohatsu is actually one of thee best outboards built.

The thing i want to know is how far apart the performance will be if any at all besides maybe a few mph on the top end.My boat is 200lbs.Btween me,wife,kid and loaded down it will be close to 800lbs or a hair bit more.So now wil the 20hp tohatsu handle all that weight o am i better off with the 15hp 2stroke.Will the tohatsu be a dog with all that weight is what i guess i want to know?

What makes me scared is who knows when the whole 2stroke outlaw thing will hit the whole u.s if indeed it does which i think it's gonna happen some time in the near future.I may as well be prepared with a new 4stroke.I just don't want to loose a major amount of performance from one to the other also.

 

[nwcove]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

if you're comfy with the brand, 5 extra horses should be quite noticable, you may loose some performance under certain situations, but gain in others. as far as the two stroke ban goes, look around for a vintage johnyrude, just cant imagine the ban not having a "grandfather" clause, allowing the use of vintage motors! (they are affordable, reliable, and very easy to work on, not to mention the fact that they are soooo nice to look at!)

 

[boater1234]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

My 15hp 2stroke yamaha is actually a brand new 2011 model.Of course we all know they stopped production in 2009 but this is a leftover i found and i have only used it twice.Actually it's a 9.9 that was coverted to a 15 with a simple reed change that was only $75.People think the carb needs to be changed which is false as it's only one part[reed valve behind the carb] that seperates the 9.9 and 15.

I will give it some thought and i will see the pros and cons.If anyone has any other good info please chime in.

 

[boater1234]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

Ok i will end this thread with this post.I have just decided to keep my 15hp yamaha as i may never see another new one again.I will just buy a 20hp 4stroke down the road and use both.Thanks for the few posts though.It's just not worth leting this motor go for less then what i paid for it.Thanks again for the posts nwcove.

 

[Sea Rider]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

Some comments, if possible have both engines. My Tohatsu 2 strokes placed on a 420 mt rib with about same passenger weight configuration runs 22 Knots at wot, it's faster than a Yam 15, because has 50 CC more. A Yam 15 is 250 CC, a Tohatsu 4 strokes is 350, with 100 CC difference, definitely you should experiment more power & torque.

By simple reed change you mean both spare valves or complete assembly with slight bigger intakes and valves ? In some engines you must change carb & complete reed valve assembly to update to next model. On others, cam, carb gasket.

Happy Boating

 

[boater1234]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

The whole reed valve was changed.It's a $75 part from yamaha.I went over the 9.9 and 15 with my marina part for part as well as a yamaha rep on the phone and every single part number was identical on both the 9.9 and 15 except the reed valves that sit behind the carb.Actually they are the same part,but the new reed valves are open all the way so it can't restrict the air flow.

That is the only difference between the 2.The carb is 100% the same.I took the outboard out after they did the job for me and there was a very noticable difference.It had alot more power on take off and i got a 4 to 5mph increase on my gps on the top end so all in all it was worth just $75 plus the $80 labor for them to do it.Also the 15hp is made at only 5000rpm so that leaves 500rpm no accounted for.I think i may be able to get a better top end with a larger prop.Right now it has a 9x9 prop but i bought a 9 1/4x101/2 size prop that should give me more top end.I am going to try it once the motor is fully broken in.I am going to buy a 20hp tohatsu down the road for the boat i have now.I am going to use this 15hp on a new either 10 or 12 ft jon boat for winter fishing here in fl.The tides run extremely low so i need a fast planning boat.I just want a little easy to move flat bottom boat for winter fishing.The boat i have now 1442 alumacraft will be used in the summer for family fun and going to the springs and beaches.

 

[Sea Rider]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

Definitely a cheap upgrade, if you would like to do same on Evi 9.9 to 15 will need to change complete reed valves assy, both gaskets and carb + hand labor, much costly update, enjoy your updated 15 HP.

Happy Boating

 

[sschefer]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

The difference between 9.9 and 15 is huge almost unbelievable if it's prop'd right but there are only a handful of props available for these motors so your limited in what you can do. The max RPM should be around 6000-6200 on that motor without hurting it. Your numbers indicated to me that you're running to big of a prop now but it may just be the only one available.

The change to the 20hp Tohatsu will blow you away compared to an upgraded 9.9. The hole shot won't be as snappy but it will impress you on the top end and troll at 1.5mph all day long. I had the Nissan 18hp and it would run right alongside a Johnson 25 that my brother had on an identical boat. He had a better hole shot but the top end was just about the same, (my brother weighs 100lbs more than me and I'm 225).

 

[boater1234]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

The rpm max according to yamaha is between 4500-5500 rpms for the 9.9 and 15hp 2stroke yamaha.Are you telling me that it is actually 6200.Because if that is the case i have not even come close to the max overall performance yet.That would be awesome if this were 100% accurate.I'm just going by what yamaha's website and what the manual says.According to the manual the 15hp 2stroke makes it's full power of 15hp at 5000rpm.Which means i have 500rpm to spare that is what i mean.

I know the little 15hp 2stroke mercs go to 6000rpm but i never heard the yamaha hitting 6000 or more.If anyone here knows this for a fact can they please chime in.For now i will go by the book stating it can go 5500rpm max unless someone else can verify this also.I don't want to blow the motor up or over rev it if that is what will happen.Now on the other hand the tohatsu or merc 20hp 4stroke has a max rpm of 6250.I am going to keep this 15hp yamaha and put it on a smaller boat for winter fishing here in fl as the tides get really,really low almost no water so i need a skinny planning boat.I have a bigger jon boat now that i am going to get a new 20hp 4stroke of some brand here soon.Probally a merc or tohatsu.Ok thanks for the info so far it's been a big help.

 

[Nathan k]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

just an idea... but could i change the reeds on a 3L mercruiser and get more power? or is it a 2 stroke thing?

 

[nwcove]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

dont think your mercruiser has any reeds, unless they're wrapped around your prop!

 

[Sea Rider]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

dont think your mercruiser has any reeds, unless they're wrapped around your prop!

Or for playing " castanets" with them after you unwrap from prop...

Happy Boating

 

[boater1234]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

Anyone for help on the question i asked?The yamaha has a max rpm of 5500 is that correct or is it actually higher then that?I know the 20hp tohatsu has a rpm max of 6250 as the mec does,[it's the same outboard pretty much].So you think i would be better off with the the tohatsu?Can there really be a big perfomance difference from a 15hp 2stroke to a 20hp 4stroke?According to most there is a very slight difference in the 2 when it comes to a 15hp 4stroke to a 20hp 4stroke.I really like the tohatsu/merc 20hp outboard.Like i said i am going to keep the 15hp 2stroke anyway but i want to know what i'm getting from a 20hp merc or tohatsu?It seems to have a ton of power.Also i am wondering if you can push more then 5500 rpms out of the 15hp 2stroke without hurting it?

 

[Sea Rider]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

If Yamaha stated max 5500 for that engine you cannot go over it unless you would like to hear a big crack, there's a big CC difference between both brands, 250 CC against 350 CC. Place a induction tach on you engine go for a wot spin and check max rpm achieved, play with different ptop pitch to have max 5500 if that worries you.

Happy Boating

 

[boater1234]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

Yes i understand the difference between the cc's but that has alot to do with the size difference i would think.The gear ratio in the yamaha is 2.08 compared to the tohatsu 2.15 which of course is better.They have done that to try and give the heavier motor that extra power to get out of the hole because of its weight.
I have seen tons of videos on you tube with the 20hp 4stroke yamaha,merc and tohatsu and it seems like they all have really good punch.I think you can't go wrong with any of them.I hear alot of people say the tohatsu/merc has a better hole shot but from what i have seen on the videos it seems to close to tell any difference.The yamaha has a ton of power as well as the tohatsu/merc.But again they weigh 115+compared to 79lbs my yamaha weighs.I wonder what the over rev is on a 15hp 2stroke yamaha?I would think it has to get to at least 200-400rpm over before the over rev kicks in.

I have a 9x9 prop on there now which is the standard one from yamaha and once broke in i am going with a 10.5 because it will be just me and my stuff in the boat so it won't be a heavy load.I'm going out tomorrow if it doesn't rain here in fl.I will post what my gps reads at full throttle with the 9x9 and once broke in i will go with the 10.5 and see how much i gain in top end speed.This motor was bought as a 9.9 and i had the marina put a new set of reed valves in the motor and it will give it tht extra 5hp or more.

Alot of people think you need to swap the carb and a few other things as i did but it is as simple as a $75 reed change to get it back to a full 15hp,imagine that.I did all the research one could possibly do to make sure that was all it was.I went over ever part with a yamaha rep on the phone and from the top of the cowl to the bottom skeg they are 99.9%identical besides that one reed valve behind the carb.

The 20hp tohatsu/merc or yamaha will have to wait till i get some more money as right now i have limited funds and come tax time i may get it.I know this is off the topic a little but i have also been thinking of a new 25hp etec,that would be a sweet motor to have on my jon boat,it would flat out get it and be new technology.I found a new manual start motor in the box for less then $2900+tax,that is a deal.I found a brand new 30hp a few mths ago for only $3000 but i didn't have the funds.A dealer got only two of them from a store that went under.They had electric start.They usually run close to $4000 or more.Well when the time comes i will decide,for now i need to concentrate on my 15hp yamaha.

 

[Sea Rider]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

You shouldn't play with prop's pitch as a wild guess, must use and induction tach to wot test both props to see max rpm at wot, if engine goes beyond recommended rpm constantly, engine will last less and you could break internal parts jamming the entire engine, if not mistaken, portable 2 strokes outboards don't have incorporated an over rev system, if so, don't play with engine....

Happy Boating

 

[boater1234]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

Yes it does have an over rev system according to yamaha and the manual.There is 2 little connector wires under the hood that looks like something can be hooked up to them.It may be tach wires i have to find out.

 

[Sea Rider]

Re: 15HP 2stroke yamaha vs 20hp 4stroke tohatsu

Anyway it's useless experiment to prop an engine with a prop that will give more rpm if the system will cut out shortly after passing max recommended rpm for than engine. Buy an induction tach which are cheap, test, take the nail out for yourself...

Happy Boating