20hp 4stroke comparisons

Hello to all.I have been going back and forth on these 20hp 4stroke motors and now in 2 weeks i'm going to purchase one.I have a question.

Is it true with 4strokes that the more displacement in a motor the more top end or more torque there is?Like as in the yamaha 20hp has the highest displacement at 362 cc's compared to like the suzuki or even the merc/tohatsu,what will be the main difference in these motors if any besides the features?

Will the tohatsu/merc be a better over all performer then all of them because of it's 2.15 gear ratio?I have a yamaha dealer right down the street and they offered me a brand new 20hp 4stroke yamaha for $2580,sounds like a deal plus i get a 5yr warranty now,so that makes it even sweeter to get.

I guess my biggest question is will the efi of the suzuki out perform the carbed motors in anyway at all?
I can only imagine that the yamaha would make my boat fly(14ft lowe rated for a 20hp,boat is 185lbs,flat bottom).

I have heard from many people that the 15/20hp yamaha is a dog that is what has steered me away.I have seen it in action on you tube and it seems to have good power.

Man why does there have to be so many motors to choose from,this is a hard choice to pick from.

Re: 20hp 4stroke comparisons

On new engines HP is measured at the prop, so having lees or more CC and gear ratio should not be an issue. At wot 20 HP Yam is same as a 20 HP Tohatsu. Same HP 2 strokes engines accelerates faster than 4 strokes and being lighter is a +. There's a huge difference between 15 and 20HP. If your boat is rated for a 20, then get a 20, boat-engine combo will perform much better than with a 15.

Happy Boating

Re: 20hp 4stroke comparisons

Ok that def helps me.The thing is i always hear everywere is more displacement =more power and top end.Or you hear there is no replacement for displacement.Just asking now,if a yamaha has 362cc's and the suzuki has 323cc's what does that mean as far as the difference between the 2 besides the features of course?

Re: 20hp 4stroke comparisons

Both delivers 20 HP at prop, other than that assume the Yam having more CC will consume more fuel at wot to achieve 20 HP and probably weights tad more than the Suzy. Try to get factory fuel consumption parameters at wot for both and check who drinks more fuel and which is heavier. Could go fot the less guzzler and lighter engine if both characteristics happens to match any of them...

Happy Boating

Re: 20hp 4stroke comparisons

Well in that case the suzuki wins hands down.

Re: 20hp 4stroke comparisons

Why would you modernize "half way" (4-stroke carbed) vs 4-stroke EFI? I cannot imagine anyone wanting to deal with a carburetor, especially on a small engine since they are very prone to issues due to the very small passages. Displacement of an engine alone has little or no meaning. A large displacement engine if everything else is equal (gear ratio and prop) should provide more push. Not I did not say more speed. I mean the boat can be loaded heavier and the engine can still tolerate the load whereas a smaller displacement may not. This also assumes the boat is the same in all instances. However, I would never, in this day and age select an engine with a carburetor if an equivalent is available with EFI.

Re: 20hp 4stroke comparisons

Thats why i'm going with the suzuki,it's efi and very lite at 97lbs.

Re: 20hp 4stroke comparisons

boater1234 said:

Thats why i'm going with the suzuki,it's efi and very lite at 97lbs.

Click to expand...

let us know how you like the suzuki. I just got a 20hp yamaha and it runs great just working on a planing issue likely unrelated to the motor. it seems to vibrate a bit more than I'd like just needs an adjustment. wish it had dual start instead of just electric though.

I was going to go suzuki but the deal on the yammy I couldn't pass up. so far great on gas. fairly big displacement difference hope the efi makes up for it

Re: 20hp 4stroke comparisons

If engine turns freely without a load while rotating tiller, adjust swivel bracket load bolt CC untill you have increased the resisstance enough, this will lessen excessive engine vibration.

Happy Boating

Re: 20hp 4stroke comparisons

I don't claim to have a lot of expertise, but in general you need two things to get horsepower: torque and RPMs. More displacement tends to give you more torque - which means the motor should have more lugging power at lower RPM. A smaller motor needs to spin faster to get the same horsepower. Check the RPM at rated horsepower and you'll probably see a difference; but with a light boat either motor will get you up on plane.

Re: 20hp 4stroke comparisons

If running any engine at minimum wot rpm parameters with any given load, you will be lugging the engine, no good, too much stress on pistons and cralkshaft wich could damage the entire block. Middle to near max wot rpm would be the way to go when at wot.

Happy Boating

Re: 20hp 4stroke comparisons

I always run my outboards near wot if not at wot unless i'm in a channel.I will be getting the suzuki in a few weeks so i will give an update asap.According to a few people i have talked to on another forum the break in peroid for the suzuki is 20hrs which i think is crazy and way to long.I have broken in all my motors the same(5 or them)i do a 10 to 15 min warm up out of the box and then drive it like i stole it and i have never had one issue with any of my outboards.I know a friend who has my 9.9hp 2stroke tohatsu from 2001 and i did the breakin i just talked about and he said it still runs like a champ today,as good as it did right out of the box.

IMO i think the manuals need to be updated.They have been the same for who knows how long and the technology has changed so much from when these manuals were printed up.All i believe u need to do with todays outboards is just vary the rpms and thats all that needs to be done,once again IMO.The old saying if it aint broke then don't fix it.It has worked for me on every motor and that is what i will continue to do.Like i said before i have owned over 15 brand new cars and have never broke in a 4stroke efi car or have been told to do so at any dealership.There is nothing wrong with following the manual,i just believe it's way outdated IMO.