1989 20 HP Johnson power upgraded to 25 HP for zero dollars

[Johny25]

Get more weight up front if you can.......will help the porpoising

 

[Siguz]

Hi,
I'm new to this forum.
I came across it while looking for a a way to boost the power from my 1989 Evinrude 20hp.

I want to do this manifold modification but I am afraid that no one will work on my motor afterwards.
I'm just starting to learn about small engines but have been working with cars for over 10 years.

What has to be done after the intake bore?
-Does the timing have to be set differently or anything like that?

I don't want to end up in a spot where regular maintenance is not enough for the motor after it has been changed.

Any input is appreciated.

Thanks!

 

[Stefan]

Siguz » 19 minutes ago[/url]"]Hi,
I'm new to this forum.
I came across it while looking for a a way to boost the power from my 1989 Evinrude 20hp.

I want to do this manifold modification but I am afraid that no one will work on my motor afterwards.
I'm just starting to learn about small engines but have been working with cars for over 10 years.

What has to be done after the intake bore?
-Does the timing have to be set differently or anything like that?

I don't want to end up in a spot where regular maintenance is not enough for the motor after it has been changed.

Any input is appreciated.

Thanks!

Hey,

It depends on the model, year and size of the motor. In my case, the 20 hp was = to the 25, 30 and 35 hp of that vintage. the only difference was the intake manifold and carb for the 30 and 35hp, and for the 25 hp model the only difference was the intake manifold.

I didnt have to do any further modifications to the engine to get the increased power.

Again, do your homework on the specific motor you would be modding. Luckily for me , my engine shared a powerhead and gearing with many different motors.

 

[Siguz]

I used the Evinrude catalog to compare mine to it's big brother 25.......... All parts match.
I checked mine (E20ECEM) against yours..... we have essentially the same motor when i look at part numbers, except mine is electric start.

My wife won't let me do it unless I'm sure that i can get regular service from a marina when we need it.
There are some things that i can do myself but there are things that i just don't have time to do.

Do you do all your work yourself?

Siguz"><span>https</span><span>://</span><span>www</span><span>.</span><span>tinboats</span><span>.</span><span>net</span><span>/</span><span>forum</span><span>/</span><span>viewtopic</span><span>.</span><span>php</span><span>?</span><span>p</span><span>=</span><span>343374</span><span>#</span><span>p343374</span><span>]</span><span>Siguz</span></a> » 19 minutes ago[/url]"]Hi,
I'm new to this forum.
I came across it while looking for a a way to boost the power from my 1989 Evinrude 20hp.

I want to do this manifold modification but I am afraid that no one will work on my motor afterwards.
I'm just starting to learn about small engines but have been working with cars for over 10 years.

What has to be done after the intake bore?
-Does the timing have to be set differently or anything like that?

I don't want to end up in a spot where regular maintenance is not enough for the motor after it has been changed.

Any input is appreciated.

Thanks!

Hey,

It depends on the model, year and size of the motor. In my case, the 20 hp was = to the 25, 30 and 35 hp of that vintage. the only difference was the intake manifold and carb for the 30 and 35hp, and for the 25 hp model the only difference was the intake manifold.

I didnt have to do any further modifications to the engine to get the increased power.

Again, do your homework on the specific motor you would be modding. Luckily for me , my engine shared a powerhead and gearing with many different motors.

 

[Stefan]

HI Siguz,

I feel like a bit of an idiot because I didn't read your original post close enough when I replied. I guess I was in a rush... So now that I have time to sit down here is a proper reply.

You have the exact same motor as me other than the electric start! Amazing motors , they are over engineered and very tough.

In doing this modification you have absolutely nothing to worry about. All you're doing by boring out the intake manifold is delivering more air to the fuel mixture. I was blown away with the results. If you're hesitating to do the mod, start with taking off the carb and intake manifold. Is the intake manifold obstructed by a key hole shape, like in the pic I posted? If so, then simply bore this out to match the carb opening and your engine will deliver more power.

No marine mechanic would not work on your engine if needed because of this mod. It's not like it has a warranty and it is voided... I did a ton of research on this mod before I did it, on iboats and other boating forums, until I was comfortable. It was definately the right call and I have had no issues with my motor because of it. As a matter of fact, my motor seemed to like the increased air - it's almost like it was starved and underpowered before.

I live in Gananoque ON, not far from you so, you know where I live, so I have alot to lose suffering your wife's wrath if the mod didn't work... I am certain that it will... Feel free to ask away, I'd be glad to offer my help, and if you want to phone or email me just send a private msg...

 

[Stefan]

Also, have a look at johny25s post on this topic. His post is a lot more detailed than mine with regard to specs and pics and he has a wealth of knowledge on upgrading motors like ours...

here is the link https://www.tinboats.net/forum/viewtopic.php?f=4&t=23898

 

[Siguz]

I'm starting the mod tomorrow.
I'll try to get as many pictures as I can and also document the process.

Wish me luck and thank for the advice :mrgreen:

 

[Stefan]

Awesome, looking forwrd to hearing about how it goes and the results it achieves for you. just on time for the boating season..

 

[Siguz]

https://drive.google.com/folderview?id=0Bx_nvDyN8sqscXotWW5ETGdvX0k&usp=sharing

The link above is to the pictures of my 20->25 mod.
The pics are numbered in sequence.

You'll notice that I didn't smooth out the opening of the manifold. I didn't because the carb covers all of the rough edges therefore not creating any kind of further turbulence and I wanted to be sure that I had enough material get a proper gasket seal. Also, the marks on the front of the manifold are from my dremel slipping (oops); they are superficial and did not affect the integrity of the surface.

Big thanks to Stefan! Thanks for the idea and thanks for the guidance.

Note: Aluminum melts when a high speed too is used. The best way to do this mod is with a drill press at low speed. I cut is better than many

Can't wait to get it out on the water

 

[Stefan]

Thank you for contributing to the thread and expanding the knowledge base. You took some great photos that will help other people make this mod... Awesome.! I just know you will be thrilled with the improvement. Let us know how it goes when you get her in the water.

 

[Siguz]

Got my motor started.
Ran like Crap and wouldn't hold idle.
Then I discovered that the carb was set to extra lean.
Turned it up a bit and now we're good to go.
Into the water this weekend.
I'll post performance numbers on the weekend.

 

[Siguz]

What a difference!
gets up to plane with 3 grown men in it!

Top speed is now 38 km/h from 23 km/h with my wife and I in it.
I'd like to get 40 km/h out of it....Any suggestions?

 

[Stefan]

Awesome! I'm glad that it worked! I couldn't beleive it the first time either.

Try this to get over 40km/h:

1-clean and wax the bottom of the boat
2-make sure your prop is in great shape
3-a dolphin on the bottom of the motor might help

Was your wife happy??? THat's the most important thing

 

[Siguz]

I agree with the Prop..... it needs one for sure.
Unfortunately I used Rock Guard for the bottom because we beach the boat daily.
The Dol-Fin does help a lot. I installed that last year.

Right now I have a 10x3; 3 blade aluminum prop.
What do you think would be a good replacement? What are you running, Stefan?

(Ps Nice to hear from you)

 

[Stefan]

Good to hear from you too...

I'm using a 10.5 inch 3 blade, which needs to be replaced... I think that the motor can take an 11 inch prop but I have to do more research on that. I have a kicker motor , a 6 hp on my boat that I use for trolling and sometimes when I am going long distances i start them both.

THe throttle on the 6 hp is stiffened to stay at constant speeds. I open it right up in conjunction with the big motor and it gives it a serious boost, probably 7 km/h more.

Are you going to be fishing on the St Lawrence at all this summer?

 

[Stefan]

Good to hear from you too...

I'm using a 10.5 inch 3 blade, which needs to be replaced... I think that the motor can take an 11 inch prop but I have to do more research on that. I have a kicker motor , a 6 hp on my boat that I use for trolling and sometimes when I am going long distances i start them both.

THe throttle on the 6 hp is stiffened to stay at constant speeds. I open it right up in conjunction with the big motor and it gives it a serious boost, probably 7 km/h more.

Are you going to be fishing on the St Lawrence at all this summer?

 

[Siguz]

I spoke with some Evinrude dealers and they've advised me to try a 10 x 15, 3 blade.
They said that going to an 11 would slow the acceleration to a point that I would be unhappy with it.
Even going to 15 pitch will reduce the acceleration but they said it would still be okay.

Now..... to find a prop that doesn't cost sooooo much especially when all of this is a gamble.

Would anyone recommend a particular supplier or brand that won't break the bank?

 

[Johny25]

Ok hold up! I am sorry but I have to interject some knowledge here. First off the dolphin will not help top speed at all.....sorry. It helps keep boat on plane at lower speed and helps boat plane out, no top end increase. In fact it can do the opposite to top speed if not set up correctly.

Second if you want the correct prop to get top speed then post your current prop specs, RPM, GPS speed and make and model of motor. This will let me know your gear ratio and recommended RPM for the motor to give you a better idea of correct prop now that you did mods to engine.

DO NOT BUY A PROP BECAUSE SOMEONE TOLD YOU OVER THE PHONE IT WOULD BE OK! TRUST ME.....You have a high risk of wasting your money and messing up your motor. They are designed to run at a specific RPM range and just guessing without proper info can take away life of your motor or ruin it entirely

 

[Stefan]

Johny25 » Today, 19:20[/url]"]Ok hold up! I am sorry but I have to interject some knowledge here. First off the dolphin will not help top speed at all.....sorry. It helps keep boat on plane at lower speed and helps boat plane out, no top end increase. In fact it can do the opposite to top speed if not set up correctly.

Second if you want the correct prop to get top speed then post your current prop specs, RPM, GPS speed and make and model of motor. This will let me know your gear ratio and recommended RPM for the motor to give you a better idea of correct prop now that you did mods to engine.

DO NOT BUY A PROP BECAUSE SOMEONE TOLD YOU OVER THE PHONE IT WOULD BE OK! TRUST ME.....You have a high risk of wasting your money and messing up your motor. They are designed to run at a specific RPM range and just guessing without proper info can take away life of your motor or ruin it entirely

Johny25, thanks for imparting your knowledge. I've read numerous of your posts and I know your knowledge of these motors is extensive to say the least.

This is motivating me to replace the prop on my engine. You say that you need the RPM at top speed with current prop.. How do I go about measuring RPM? Is there an aftermarket Tacho tool you can buy and attach to the outboard to give a reading? I've seen them for motorcycles, but is there something similar for outboards? If so, where is the best place to buy these?

 

[Siguz]

Stefan » 28 May 2014, 21:47[/url]"]

Johny25 » Today, 19:20[/url]"]Ok hold up! I am sorry but I have to interject some knowledge here. First off the dolphin will not help top speed at all.....sorry. It helps keep boat on plane at lower speed and helps boat plane out, no top end increase. In fact it can do the opposite to top speed if not set up correctly.

Second if you want the correct prop to get top speed then post your current prop specs, RPM, GPS speed and make and model of motor. This will let me know your gear ratio and recommended RPM for the motor to give you a better idea of correct prop now that you did mods to engine.

DO NOT BUY A PROP BECAUSE SOMEONE TOLD YOU OVER THE PHONE IT WOULD BE OK! TRUST ME.....You have a high risk of wasting your money and messing up your motor. They are designed to run at a specific RPM range and just guessing without proper info can take away life of your motor or ruin it entirely

Johny25, thanks for imparting your knowledge. I've read numerous of your posts and I know your knowledge of these motors is extensive to say the least.

This is motivating me to replace the prop on my engine. You say that you need the RPM at top speed with current prop.. How do I go about measuring RPM? Is there an aftermarket Tacho tool you can buy and attach to the outboard to give a reading? I've seen them for motorcycles, but is there something similar for outboards? If so, where is the best place to buy these?

I've read many posts from both you guys and you are the ones that have inspired me to learn more about these motors.

Johny25:
I agree the Dol-fin does not help top speed in any way but it does help get up to plane much quicker.

As Stefan asked; how can we check our RPM without any gauges?
It surely doesn't sound like it's over/under reving.

The only mod that I've done is the intake manifold.
-Currently running a 10in 13p 3blade
I looked online at the evinrude parts catalog and it listed a 10*15 prop suitable for the motor.
-Model# CE20TECEM (E20ECEM)
-1989 eveinrude 20hp (thru-hub)
-GPS speed is 38km/h

Thank you for your input