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

[Stefan]

longshot » 13 minutes ago[/url]"]

Stefan » 31 Aug 2013, 14:01[/url]"]

longshot » Today, 09:55[/url]"]I just did something very similar to this on my 2003 tohatsu. It needed the carb overhauled and I discovered the 9.9/15/18 were all the same except for the carbs. So I ordered a new 18 carb runs great in the tank I will be trying it out at the lake in the morning

How did it go? did you notice a big diference in speed and power??

I took it to the lake today and ran it hard. Burned up about 5 gallons of gas. We had a cooler two bags of gear tackle boxes live well full trolling motor and battery and full fuel tank. We were able to obtain 21 mph on the gps and it was very rough out. Before I changed carb and raised jack plate all I could get was 16 mph plus it started on the first pull every time. My boat is a G3 1544

That is pretty great improvement - 33% on speed! And probably a whole lot less frustration with the boat planing quicker I bet... Although the fuel consumption would be higher, who gives a damn when you're having that much fun! wooohoooo

 

[longshot]

We made a 45 min WOT run across the lake and then 45 min back and it was really rough. Probably could have gotten a little more speed if we were not jumping boat wakes and wind blown waves the whole way. My wife wants to kill me

 

[Stefan]

longshot » 11 minutes ago[/url]"]We made a 45 min WOT run across the lake and then 45 min back and it was really rough. Probably could have gotten a little more speed if we were not jumping boat wakes and wind blown waves the whole way. My wife wants to kill me

haha that's awesome! well one benefit with the extra speed is that you can get out of rough water situations faster, or conversely, enjoy them that much more!

 

[shawnfish]

Stefan » Today, 20:23[/url]"]

longshot » 11 minutes ago[/url]"]We made a 45 min WOT run across the lake and then 45 min back and it was really rough. Probably could have gotten a little more speed if we were not jumping boat wakes and wind blown waves the whole way. My wife wants to kill me

haha that's awesome! well one benefit with the extra speed is that you can get out of rough water situations faster, or conversely, enjoy them that much more!

and benefit 2 is maybe she wont wanna go as much and then you can concentrate on the fish without her yappin your ear off....at least mine does god bless her lol!

 

[shawnfish]

hey Stefan im gonna cross reference that stuff too, not because I think you need help I just like to do it and will in a sober manner this time lol! one plus is when your ready you can have what you find and what I find out and if we both have the same results it maybe give you some reassurance.......oh and did you get my email about the close ups on the tape?

 

[Plasticmotif]

newly listed:
https://www.ebay.com/itm/CARBURETOR-FOR-A-1997-EVINRUDE-30HP-OUTBOARD-MOTOR-P-N-0435376-/350868278612?pt=Boat_Parts_Accessories_Gear&hash=item51b1610d54&vxp=mtr

I don't think it'll work on my model motor though.

 

[Plasticmotif]

Man, I've been looking on Ebay for ages. I've also been looking on Craigslist and LSN here and can't find anyone to even trade with.

I guess 30/35 Tillers aren't common around me. Find the carb for my year motor isn't easy either.

Bah!

 

[shawnfish]

Plasticmotif » 09 Sep 2013, 21:34[/url]"]Man, I've been looking on Ebay for ages. I've also been looking on Craigslist and LSN here and can't find anyone to even trade with.

I guess 30/35 Tillers aren't common around me. Find the carb for my year motor isn't easy either.

Bah!

what carb are you looking for?

 

[longshot]

I got mine from boats.net

 

[T Man]

A 5hp gain almost doubled top end? This seem off to anyone else but me?

 

[Plasticmotif]

Ive got a 90 20 hp. I've bored it to the same as OP. I'd like more power. So, anything above 25 that'd work on my motor.

Also, T man of you're not able to plane the boat you'd notice a big difference.

 

[Plasticmotif]

My diligence paid off.

Just got this: https://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=111168222610

Asking if he's got a 30 HP intake to go with it.

 

[Plasticmotif]

I had a chance to take my boat out to a proper lake today. Previously, I was only able to do about 16-17 mph with myself and fishing gear. The boat wouldn't get on plane. It just pushed through the water. I did the carb boring to make my boat a 25. I took it out a few times with the wife and kid on a very small lake (90 acres) It was able to get out on plane but I wasn't able to really run her that well.

Today, I took her out. Motor seems to idle well. Seems to be breathing much better. Motor just flat out sounds better. I verified speed today with GPS again. I was able to get up to get on plane easily and maintain a speed of about 24-25mph. Wide open wasn't much difference. Backing off the throttle some I was able to do 22-24 MPH, wide open 25-26 mph.

That's a significant increase!

I've gotten a 30HP carb and 30 HP intake on the way as well. I'll install them. Hopefully, I'll be able to get about 30 MPH. That's pretty fast. My boat's handling felt great at 25 mph. Well see where the extra 5 horses takes us!

 

[Stefan]

Plasticmotif » 14 Sep 2013, 20:00[/url]"]I had a chance to take my boat out to a proper lake today. Previously, I was only able to do about 16-17 mph with myself and fishing gear. The boat wouldn't get on plane. It just pushed through the water. I did the carb boring to make my boat a 25. I took it out a few times with the wife and kid on a very small lake (90 acres) It was able to get out on plane but I wasn't able to really run her that well.

Today, I took her out. Motor seems to idle well. Seems to be breathing much better. Motor just flat out sounds better. I verified speed today with GPS again. I was able to get up to get on plane easily and maintain a speed of about 24-25mph. Wide open wasn't much difference. Backing off the throttle some I was able to do 22-24 MPH, wide open 25-26 mph.

That's a significant increase!

I've gotten a 30HP carb and 30 HP intake on the way as well. I'll install them. Hopefully, I'll be able to get about 30 MPH. That's pretty fast. My boat's handling felt great at 25 mph. Well see where the extra 5 horses takes us!

Thanks for the Update! I've been away for two weeks with no online accessm. I am very happy to read that you have had success with your upgrade and were able to locate a 30 HP carb. ... tHAT is some excellent engine improvement... With regard to your 30 HP carb, and there not being a slow idle screw on it.. I'm not sure how you'd go about adjusting the idle ... I'll see what I can dig up and post what I find.

 

[Stefan]

Plasticmotif » 14 Sep 2013, 20:00[/url]"]I had a chance to take my boat out to a proper lake today. Previously, I was only able to do about 16-17 mph with myself and fishing gear. The boat wouldn't get on plane. It just pushed through the water. I did the carb boring to make my boat a 25. I took it out a few times with the wife and kid on a very small lake (90 acres) It was able to get out on plane but I wasn't able to really run her that well.

Today, I took her out. Motor seems to idle well. Seems to be breathing much better. Motor just flat out sounds better. I verified speed today with GPS again. I was able to get up to get on plane easily and maintain a speed of about 24-25mph. Wide open wasn't much difference. Backing off the throttle some I was able to do 22-24 MPH, wide open 25-26 mph.

That's a significant increase!

I've gotten a 30HP carb and 30 HP intake on the way as well. I'll install them. Hopefully, I'll be able to get about 30 MPH. That's pretty fast. My boat's handling felt great at 25 mph. Well see where the extra 5 horses takes us!

Thanks for the Update! I've been away for two weeks with no online accessm. I am very happy to read that you have had success with your upgrade and were able to locate a 30 HP carb. ... tHAT is some excellent engine improvement... With regard to your 30 HP carb, and there not being a slow idle screw on it.. I'm not sure how you'd go about adjusting the idle ... I'll see what I can dig up and post what I find.

 

[Plasticmotif]

I figured it out. It's an 88, not a 91. The low speed idle is set on the top orifice plug location on other years!

 

[Plasticmotif]

So, I figured I'd post some pictures to help out others wanting to do this mod.

After having removed the 20 HP intake, it's clearly throated down. I had already started filing a bit to see how soft the metal was/is. It's soft.
https://img.photobucket.com/albums/v518/plasticmotif/photo_zpsdd0da165.jpg

Difference in carbs. 20HP on top 30 HP on bottom.
https://img.photobucket.com/albums/v518/plasticmotif/photo4_zpscf06ead6.jpg

New intake/Gasket 30HP, much larger:
https://img.photobucket.com/albums/v518/plasticmotif/photo3_zps16f302cf.jpg

Uh oh, some fuel line intake nipples are larger than others. I just forced the line on. Rubber stretches!
https://img.photobucket.com/albums/v518/plasticmotif/photo5_zps163e897b.jpg

 

[jasper60103]

Thanks for sharing. Please let us know how the water test goes.

 

[Stefan]

This is really good stuff. Thanks a lot guys, for posting all of this info for others to benefit... i hope everyone is happy like me with their faster boats that now go on plane!

 

[Plasticmotif]

Well, I hit 30 MPH with the 30!

I was porpoising by myself. I need to change the trim of my motor. Ran great. Going to pull the plugs and make sure it's not running too lean or too rich.

It used noticeably more gas!