The new 4-stroke 15 and 20...

greenmtnboat

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Apr 9, 2010
Messages
18
I have seen some older threads re: 9.9 to 15 conversions. Now, it seems to me that the newer 15's share the same platform with the 20's. After looking at the specs on these, I am really curious where the differences lie.

Horsepower, displacement, bore & stroke, gear ratio, dry weight.....all appear to me to be identical. The only difference I see is the max rpm's at wot are 5000 - 6000 for the 15 and 5400 - 6100 for the 20.

Can someone more knowledgeable than myself about outboards (probably most of you!) shed some light on where the real differences are, and if that conversion is a possibility?

Forgive me if I have missed discussion on this topic, all of my searches have turned up the 9.9 to 15 threads.

Thanks, and what a dynamite site! Very glad to have found you all!

Cheers,
 

greenmtnboat

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Apr 9, 2010
Messages
18
Re: The new 4-stroke 15 and 20...

:D:


GAH! After reading some more threads, and especially responses, to other similar threads I am tempted to just delete this thing right out of the gate. I am thinking not as simple as swapping a carb....

LOVE my 15! :redface:
 

sschefer

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4,530
Re: The new 4-stroke 15 and 20...

:D:


GAH! After reading some more threads, and especially responses, to other similar threads I am tempted to just delete this thing right out of the gate. I am thinking not as simple as swapping a carb....

LOVE my 15! :redface:

The Tohatsu 20 is a great motor. The 18 was also. I suspect the 20 came from the 18 not the 15. I think the 15 came from the 9.9. because the weight is close enough. The 18 was a heavier motor and the 20 weighs about the same as the 18. That's about all I can do for guessing.

My personal opinion is that you shouldn't mess with perfection and the Tohatsu small motors are about as perfect as they come. If they weren't every manufacturer wouldn't rely on them to fill out their small motor product lines.
 

RRitt

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Mar 30, 2006
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3,319
Re: The new 4-stroke 15 and 20...

This thread reminds me .... I have often wished that I could figure out how to put my riding lawnmower engine on my small boat. As soon as I have the slightest problem I can just throw it away since the entire engine is less expensive than single trip to the marina.
 

JimXeod

Seaman Apprentice
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Feb 26, 2009
Messages
46
Re: The new 4-stroke 15 and 20...

Actually the new 15 and 20 ARE the same except for the carb (jets and main nozzle) and prop pitch. I have confirmed that it is just that simple. Bear in mind this is for the 2009 and newer 15's. Has to be the 351cc verison. The 08's were different.

See this diagram

www.marinepartsplus.com/catalog/mercury_4/serial/15_Carb_2CYL_4-STROKE/898103160/13934-100

I was going to do the swap soon. I plan on just doing the carb internals. If you get them make sure you get the right ones, as they are different for Tiller and Remote. I posted this question months ago, and got nothing but "guesses" and "probably not's" until Tohatsu guru helped out on the Tohatsu side, and confirmed, it is just a carb difference.

Upon looking into it, they share the same carb, just different nozzle and jets. I will say this, this 15 feels as strong as a 2-stroke 15 as it is. Very strong for a 15 4-stroke!

Hopefully I have given some help!
 

boater1234

Master Chief Petty Officer
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Jan 6, 2010
Messages
869
Re: The new 4-stroke 15 and 20...

I have been trying to find the answer to this question and i can't get any hard facts on it till today.After i called tohatsu and merc 10 different times[15/20 merc and 15/20 tohatsu are the same motor except the front shifter and decals.

so i called them and finally i got 2 people with some knowledge for once and one women from merc told me that there was 7 different things on a 15 to get to a 20hp but would only tell me a few of them which was the carb of course,ignition and there was a few other things that they can't mention so people can't modify the engine and void your warranty.

So i called tohatsu and asked them the same thing and did not mention what merc said until they were done to see if there was a conflict in there stories and in amazement they were very close to eachother.Then i come here and i hear it is just the carb man i am getting more confused by the day.

I want to get a 15 but if the 20 has that good extra torque then i need to go that way but now what do i do?Go 15 or 20,sounds like a substancial difference in performance but that is why i'm here to find out before i go friday and buy the 15 and should have bought the 20.any real good help is this not right what they told me and is the performace that much difference?
 

JimXeod

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Feb 26, 2009
Messages
46
Re: The new 4-stroke 15 and 20...

I have been trying to find the answer to this question and i can't get any hard facts on it till today.After i called tohatsu and merc 10 different times[15/20 merc and 15/20 tohatsu are the same motor except the front shifter and decals.

so i called them and finally i got 2 people with some knowledge for once and one women from merc told me that there was 7 different things on a 15 to get to a 20hp but would only tell me a few of them which was the carb of course,ignition and there was a few other things that they can't mention so people can't modify the engine and void your warranty.

So i called tohatsu and asked them the same thing and did not mention what merc said until they were done to see if there was a conflict in there stories and in amazement they were very close to eachother.Then i come here and i hear it is just the carb man i am getting more confused by the day.

I want to get a 15 but if the 20 has that good extra torque then i need to go that way but now what do i do?Go 15 or 20,sounds like a substancial difference in performance but that is why i'm here to find out before i go friday and buy the 15 and should have bought the 20.any real good help is this not right what they told me and is the performace that much difference?

This conflicts with what Tohatsu Guru had stated. And, to be honest I trust him more than some of these reps on the phone.
 

sschefer

Rear Admiral
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Messages
4,530
Re: The new 4-stroke 15 and 20...

Tohatsu made the 20 for folks just like you.. You descibed your needs really close to what the marketing material at Tohatsu says. Buy it.
 

boater1234

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Jan 6, 2010
Messages
869
Re: The new 4-stroke 15 and 20...

Hey jimxeod how are u? That is why i wrote that for him to chime in and any others to fill in.I will never say tohatsu guru is wrong i'm just confused that is it and i just wanted to here his input on what they told me.I told them on the phone that i'm not the smartest when it comes to outboards as far as how they are built but that sounds like a stretch about 7 different things when the powerheads are identical and made by the same people and they did not like that but it does sound fishey to me.

Tohatsu guru lives in fl like me,i guess he works at a marina i guess so he should know first hand i would guess.I found the merc 20hp electric start for $2509 after calling no b.s 40 marinas in a 500mile radius.All i want is a manual start and the cheapest i found it was $2579 and the merc for $2509 is last yrs model same as this yr but why not get electric for cheaper.

The tohatsu is cheaper but u get a 3yr instead of 5yrs and that is a good deal if u ask me for the same motor.I found the tohatsu for $2357+tax at a local dealer but if he goes under there is no dealers for hundreds of miles so that is the advantage of the merc one on every corner and a 5yr warranty.

I have thought of the 20hp yamaha to because i can get a 5yr warranty and for $30 more i can get a extra yr for a total of 6 for $2689+tax out of the box.From what i hear the merc or tohatsu has better torque because of the 2:15 gear ratio compared to a 2:08 in the yamaha,is that a huge difference can anyone help me on that?Or is that to close to notice that on a small boat.thanks for any help on that.I want to purchase by friday so any input on that is great,what is the power difference between the merc 20hp and the yamaha20hp?
 

JimXeod

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Feb 26, 2009
Messages
46
Re: The new 4-stroke 15 and 20...

Tohatsu guru lives in fl like me,i guess he works at a marina i guess so he should know first hand i would guess.I found the merc 20hp electric start for $2509 after calling no b.s 40 marinas in a 500mile radius.All i want is a manual start and the cheapest i found it was $2579 and the merc for $2509 is last yrs model same as this yr but why not get electric for cheaper.

His shop is in Tampa, I have been to it to pick up a part when I had my Tohatsu. I feel bad calling it a shop, since he is like the top Tohatsu dealer in the US! He is Internetoutboards.com, great guy too.

Anyway, I have held off on the carb swap until now because I went up an inch of pitch with a stainless prop, and this motor (15) literally hauls *** on my 11' Inflatable!

As a side note, owning both Tohatsu and now a 2009 Mercury I have noticed some differences that are nice. I don't know if they are worth hundreds more, and it may be that my Tohatsu was a 2006, but I'll let you be the judge.

1) Merc has grease fittings on steering tube, clamp bracket ect. My Tohatsu did not. I am big on maintenance so this was nice.

2) More stainless parts on the Merc than Tohatsu IE: Tiller throttle shaft, shift linkage, bracket hardware, ect. Tohatsu had zinc plated parts.

3) Shift through the tiller. This is way better for me than the front mounted shifter. One hand does it all. The tiller locks in the up position as well, and has a stop switch that attaches lanyard, or you do not have to use the lanyard. The Merc tiller is MUCH beefier too.

All in all small things, but the Merc SEEMS better made. We all know it is not, because Tohatsu makes them. I would not hesitate to buy a Tohatsu again, I just got a killer deal on this Mercury. (2009 low hour, freshwater motor for $1750 with balance of warranty) Couldn't pass it up. I really don't worry about warranties on these motors. Most everything that goes bad is not warranty stuff, carb cleaning, ect. In 3 Mercs, and a Tohatsu no issues ever that caused a part failure do to a warrantable issue. They are VERY solid. Run good gas, run gas out when done, flush em out, and don't overfill the oil, and they will run a long time.
If I were buying a 250hp 4-stroke it would be a WAY different story on the factory warranty, beleive me.
Jim
 

sschefer

Rear Admiral
Joined
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Messages
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Re: The new 4-stroke 15 and 20...

Tohatsu Guru please chime in if I'm wrong... Last I heard was that the small motors for all major manufacturers we're comming out of Tohatsu in one form or another. There probably are seven differences, things like tillers, covers, bells and whistles might be unique but once you pop the hood it's all pretty much the same.

What you might find is that Manufacturers don't want you to know that they're all the same so sometimes they'll round down numbers when others are rounding up to make them seem different or maybe they will spec a small production run difference like a different L/U gear ratio to make them seem different.

Not sure if a Merc Dealer could get Warranty re-imbursment from Tohatsu but they'd likely have most of the parts on the shelf.
 

boater1234

Master Chief Petty Officer
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Jan 6, 2010
Messages
869
Re: The new 4-stroke 15 and 20...

jIMXEOD i was going to buy from onlineoutboards .com but i talked to a guy and he wasn't the nicest fellow also he could have been having a bad day,but i called internetoutboards.com and talked to a fellow and a way different attitude there.They answered all my questions,i think they sell suzuki to don't they?I think the two places are part of one another but i could be wrong.

I swear the guy said that the 2 were part of a whole big distributing company but correct me if i'm wrong.My biggest thing is i am stuck on 4 different motors the tohatsu,merc,or yamaha 20hp 4stroke or the suzuki 15hp which i'm growing more fonder of everyday,it seems to be a well built engine and the lightest at 97lbs.Will 17lbs be that big of a difference and also the displacement is smaller at 302 instead of 351 and 362 so what engine would give me the best performance for a 1436ft lowe at 180lbs the boat and me at 260lbs and my bro at 250lbs and maybe 250lbs or more likely less just a round about number.

I'm looking at the yamaha and suzuki gear ratio at 2:08 and the tohatsu/merc at 2:15 which should generate more torque or am i wrong,i need help on that.I want to purchase soon and want to get the best info i can before i buy.p.s about the warranty/The reason i like the long warranty is down the road i want a bigger boat and that will help with resale big time trust me on that.The merc has 5yrs the tohatsu has 3,suzuki3,and the yamaha5 and can option for a extra yr for $30 more dollars and have six yrs that is outstanding and i can use it for 3 or 4 yrs and still have 2 to 3yrs left on the warranty for great resale.I want to know what is the best power fit for my boat and thanks for any help.

I'm nervous to get the yamaha because i hear from people that it has no get up and go is this a fact or nonsense?That is the closest dealer to me and they can give me a whale of a deal on a new 20hp yamaha i just need to be sure they have good power that is it.
 

JimXeod

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Messages
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Re: The new 4-stroke 15 and 20...

I think the biggest issue here is you might be overthinking this one a little tto much. I have no experience with Suzuki at all. As for the others you mentioned, Yamaha, Mercury, Tohatsu, I think you will be happy with any of them. Based on you load requirements I think you should just get a 20, rather than wanting a little more oomph later.

If you get a 15, I would get the largest displacement. Changing prop pitch will help you tune it better.

Don't worry about a mile or two per hour on top speed, you may not even notice. Again, a change in prop pitch can net some good results.

Don't overthink it my freind, buy your motor and go have some fun with it!!
 

boater1234

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Re: The new 4-stroke 15 and 20...

U are probally right i just don't want to make a mistake with the 15 instead of the 20 but on the other hand what a price differece for 5hp.I can get a new merc or suzuki for $2050 and the 20 starts at $2550 what a difference.I can live with a few mph difference for overall speed it is just that i need the max torque out of the hole that is all.

I had a question on the suzuki about 6mths ago on the suzuki 15hp and i got a post today and the guy said on a 1442 jon boat which is bigger then mine 1436 he gets 24.5mph with him in it and him,wife,and kid 21mph not to bad for a 15 if u ask me.That is also a 302 displacement as the merc is 351 or yamaha is 362 even better. so i would guess the merc would have more power am i right?
 

JimXeod

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Re: The new 4-stroke 15 and 20...

I would think so, plenty of torque on my 15. Plus, on an inflatable there is more drag. With a 10 pitch prop I run 27.2 with me, the wife, dog, and gear.
Don't think I would notice an extra 1 or 2 mph.
 

boater1234

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Jan 6, 2010
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869
Re: The new 4-stroke 15 and 20...

What motor did u say u had?That is a amazing top speed for a 15hp motor,is that gps or just a round about guess.No problem getting on plane at all shoots right out of the hole huh.
 

TOHATSU GURU

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Jul 22, 2004
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6,164
Re: The new 4-stroke 15 and 20...

In no particular order:

The only difference between the 15 C and 20 C is the carb. I have never examined a 15 C carb and compared it to a 20 C carb to see if the body is different, but I would be careful about just changing the jets. If there is a body difference you may find yourself with too much fuel and too little air going through the carb. Next time I have an opportunity I'll measure them out.

I don't think any point in Florida is more than 35 miles from a dealer.

Theoretical crank shaft engine torque is not relevant as you have fixed gearing.

The 20 Mercury/Tohatsu/Nissan outperforms the Yamaha and Honda in hole shot and WOT...Have not tested one against the Suzuki yet.

Displacement is no longer relevant as more is done with tuning. IE Raw cubes in comparison from one OB to another will not tell you the truth.

The Mercury comes with a five year warranty only if the particular dealer you buy it from pays for it out of their own pocket. It's an additional expense for the dealer and a lot of them aren't providing it. If you get a Mercury make sure they put it on your sales receipt, wait two weeks and then call Mercury to see if you really have it.

The part differences were due to model year rather than brand...However, the shift is different, the manual tilt system is different and the cowling is different. I prefer the Tohatsu shift system as it is more durable, but the Mercury system is more convenient.

In the U.S. Tohatsu/Mercury/Nissan from 30 down are Tohatsu products. Suzuki is Suzuki. Honda is Honda. Yamaha is supposed to be Yamaha, but I think they are doing some production with Selva in Europe. If they are it's not a bad thing though.
 

boater1234

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Jan 6, 2010
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Re: The new 4-stroke 15 and 20...

Thanks for the chime in guru,i tried to send u a pm but i guess u don't except them thats cool.I heard u work at internetoutboards,i was going to go down there to get a tohatsu if i buy one which is still up in the air.So do u think for the small boat i have the 15hp would do great because i'm on a limited buget and the difference in price is different at your price the 15 is $2200 and the 20 is $2480 $260 difference not as bad as merc that is for sure as a 15 merc i found for $2050 not to bad but then u go to a 20 wow it jumps to $2700 or more that is nuts.The suzuki is not bad at $2050 and i hear great things about it all over and dealers who sell it say customers love them.

Boat and motor super stores which i'm sure u know who they are sell yamaha,merc,honda and suzuki and they perfer the suzuki 15hp over all there other 15's it is the lighest at 97lbs but this is a tough one for me.I should not let the warranty get in the way as these are all good motors and the chances of something happening is slim if u take care of it.


I have had 2 tohatsu's and loved them both but were 2strokes and this will be my first 4stroke i have ever used on my boat.Like u were saying the way it is geared the tohatsu 15 is geared at 2:15 and the suzuki is at 2:08 so the torque edge should be tohatsu right,but the suzuki is 17lbs lighter so i do not know if that would come into play,anyway thanks for the advice and hope to hear anthing u might add to this.
 

TOHATSU GURU

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6,164
Re: The new 4-stroke 15 and 20...

I'm a big believer in getting an engine with the most hp within the frame size. So, the 20 in the Mercury/Tohatsu would be the one I would want. You should get about 3 mph more at WOT with the 20 than the 15. I'm thinking that a 20 would do around 28 or 29 WOT on your boat, but it might be a little slower or faster depending on load. If you want a 2010 Mercury we have those for $2625.00 with the 5 year warranty, but we would have to order it in and that would take 4 business days. I haven't run the 15 Suzuki yet so I can't give you a valid comparison. Here's the thing. It doesn't really matter what brand of outboard you buy. Yamaha, Suzuki, Honda, M/T/N, all are good and you should be pleased with any of them. Like Jimexod said, you might(I would say are) be over thinking this. I would say just pick a brand and go boating.
 
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