1990 evinrude 120 4600rpm WOT enough?

[archcycle]

Re: 1990 evinrude 120 4600rpm WOT enough?

I would definitely like some help getting this all identified. I didn't get to do anything last night other than put the prop on though, wound up going to look at houses and then the Ravens game came on.. As said I know it's not the prop I was looking for, but they gave me one that's nearly perfect for my poor shape one for a $0 trade so I figured what the heck.

As soon as I have a chance that 2 or 3 screw check is on the immediate agenda.

As for the identification of the lower, is that just going to require verifying what the gear ratio is? At risk of sidetracking the conversation, I'm hesitant to remove the lower after doing it a lot of times resolving a cooling issue and shifting issue (first rebuilt lower searching for why I had no reverse then resolved with the shift shaft adjustment) which would be fine were it not for lots of trouble with the water tube that had been mistreated by a previous owner but is sealed and good right now.

 

[nymack66]

Re: 1990 evinrude 120 4600rpm WOT enough?

No need to remove the LU here are the instructions again..
Take the cowling of the engine off and remove the spark splugs from the engine. Rotate the flywheel by hand until the #1 top dead center mark is lined up with the timing marker on the front of the engine and mark the 2 points. Now put the engine in forward and mark where the propeller is at. Now rotate the flywheel by hand counting the revolutions of the flywheel and propshaft until the prop makes 1 full revolution. If you rotate the flywheel just shy of 2 full turns to one rotation of the prop you have a V6 lower unit. If you get 2 and 1/4 turns of the flywheel to one revolution of the prop, you have the V4 lower.

 

[nymack66]

Re: 1990 evinrude 120 4600rpm WOT enough?

Here you go you can follow this one also, lets see the replies will be interesting..
http://www.screamandfly.com/showthr....prop-diameter-...gear-ratio...top-speed.-huh

 

[archcycle]

Re: 1990 evinrude 120 4600rpm WOT enough?

I ordered carb rebuild kits on Friday and decided to knock all of this out at once and they came in this morning. So I didn't take anything apart yet but I did go out on Sunday with the 15x17. Topped out at 37mph with a normal load and great water conditions and under those circumstances it would have been at least 40 with the 14.75x19. RPMs no meaningful change. Does this seem odd to you?

 

[wilde1j]

Re: 1990 evinrude 120 4600rpm WOT enough?

Forget about speed for now, it's RPM that's important. 2" less pitch should have yielded ~ 300 more RPM or ~ 4700. You need to be more precise with the RPM (i.e. somewhere around is not too good ... ain't that hard to nail). Engine life is substantially reduced by too low WOT RPM and you need to get 5800, not 5500.

 

[archcycle]

Re: 1990 evinrude 120 4600rpm WOT enough?

Forget about speed for now, it's RPM that's important. 2" less pitch should have yielded ~ 300 more RPM or ~ 4700. You need to be more precise with the RPM (i.e. somewhere around is not too good ... ain't that hard to nail). Engine life is substantially reduced by too low WOT RPM and you need to get 5800, not 5500.

More specifically prevailing conditions had it maxing out between 4400-4600 on the old prop depending on if the seas would let me get into the trim, and this one it went 4500 with seas that let me just get into the trim.

edit:it's worth mentioning I bought this tach new in October

 

[wilde1j]

Re: 1990 evinrude 120 4600rpm WOT enough?

Something's not right here, but you clearly need way lower pitch (i. e. 13"). Your WOT needs to come up ~ 1200 RPM.

 

[ezeke]

Re: 1990 evinrude 120 4600rpm WOT enough?

I ordered carb rebuild kits on Friday and decided to knock all of this out at once and they came in this morning. So I didn't take anything apart yet but I did go out on Sunday with the 15x17. Topped out at 37mph with a normal load and great water conditions and under those circumstances it would have been at least 40 with the 14.75x19. RPMs no meaningful change. Does this seem odd to you?

If you had a 15 spline gearcase that was shipped with a 1990 140 or 120 it would have a gear ratio of 2.25. At that ratio, 37 MPH is the maximum theoretical (possible) speed with a 19 pitch propeller at 4600 RPM.

On the other hand, if you had a true V6 gearcase it would have a ratio of 1.86 and the theoretical maximum speed at 4600 RPM would be 44 MPH with a 19 pitch prop.

Since with the 2.25, 40 MPH is impossible, let's assume that your tachometer is correct and that you have a true V6 15 spline gearcase.

In that case you will need a 15 pitch propeller to reach the same speed (40) at 5800 RPM assuming the same 9% slip indicated.

 

[archcycle]

Re: 1990 evinrude 120 4600rpm WOT enough?

On the other hand, if you had a true V6 gearcase it would have a ratio of 1.86 and the theoretical maximum speed at 4600 RPM would be 44 MPH with a 19 pitch prop.

This is eerily accurate.

 

[archcycle]

Re: 1990 evinrude 120 4600rpm WOT enough?

The verdict is in. V6 gearcase. Too bad it didn't come with this prop on it or I could have saved some trouble

http://cid-257fa7bb15f4822f.office.live.com/self.aspx/.Public/Gearcase.wmv

It's one full turn, one full turn, one quarter turn. So. What now?

Edit: I didn't have it in N then put it #1 TDC, I had it in F and set it to #1 TDC, but this seems pretty conclusive going well past one full rotation on two turns.

 

[daselbee]

Re: 1990 evinrude 120 4600rpm WOT enough?

The verdict is in. V6 gearcase. Too bad it didn't come with this prop on it or I could have saved some trouble

http://cid-257fa7bb15f4822f.office.live.com/self.aspx/.Public/Gearcase.wmv

It's one full turn, one full turn, one quarter turn. So. What now?

Edit: I didn't have it in N then put it #1 TDC, I had it in F and set it to #1 TDC, but this seems pretty conclusive going well past one full rotation on two turns.

I THINK what was posted by Andrew is the V6 gearcase has a 1.86 to 1 ratio.
You might want to go back and re-read.
Looks to me like you have the 2.25 V4 gearcase.

 

[archcycle]

Re: 1990 evinrude 120 4600rpm WOT enough?

I THINK what was posted by Andrew is the V6 gearcase has a 1.86 to 1 ratio.
You might want to go back and re-read.
Looks to me like you have the 2.25 V4 gearcase.

At 2 turns it was already a little bit past one full revolution, and at 2.25 turns it was about one and a half revolutions. 1.xx turns of the flywheel rotated the prop one full revolution, so it's definitely not 2.25 to 1 if I understood him correctly.

 

[archcycle]

Re: 1990 evinrude 120 4600rpm WOT enough?

As for if its a 120 vrs a 140 remove the air cover and look at the butterflies if 2 screws 120, 3 screws 140 !

So here that is. Anyone else count 3?

 

[boobie]

Re: 1990 evinrude 120 4600rpm WOT enough?

This may help you. Get a big caliper and measure the g/c out side diameter in front of where the prop goes. V-4 is 4 1/8 " . V-6 is 4 5/8 ". Don't forget one thing, Back in '85 the V-4 loopers used a V-6 size g/c but had different gear ratios than V-6. I have a different way to check gear ratios on the mtr but it gets rather lenghtly.

 

[nymack66]

Re: 1990 evinrude 120 4600rpm WOT enough?

This is what was quoted to me in 2008, I used it to correct the EXACT same issue you are experiencing may God bless Ferm and Lord Skool for this information.
Here it is unedited ...
Your pictures and your model number comes out to a 20" shaft, and your certain you have a 15 spline shaft. So this means like LORD SKOOLS said, you got the wrong lower most likely. The 15 spline 20" leg lower is one RARE bird to find, so somebody probably swapped in a V6 leg. Problem being that the V4 don't have the power to spin a 1.86:1 ratio and make any power. Sounds like your gonna need another lower unit. The first thing I would do at this point is get a rough idea of your gear ratio. Take the cowling of the engine off and remove the spark splugs from the engine. Rotate the flywheel by hand until the #1 top dead center mark is lined up with the timing marker on the front of the engine and mark the 2 points. Now put the engine in forward and mark where the propeller is at. Now rotate the flywheel by hand counting the revolutions of the flywheel and propshaft until the prop makes 1 full revolution. If you rotate the flywheel just shy of 2 full turns to one rotation of the prop you have a V6 lower unit. If you get 2 and 1/4 turns of the flywheel to one revolution of the prop, you have the V4 lower.

 

[archcycle]

Re: 1990 evinrude 120 4600rpm WOT enough?

This is what was quoted to me in 2008, I used it to correct the EXACT same issue you are experiencing may God bless Ferm and Lord Skool for this information.
Here it is unedited ...

So that's what I did and it is 1.86 to 1.

Opinions on my butterfly screws? I guess I have most bizarre case scenario here. Maybe I will just start taking pictures of part numbers and photocopying parts diagrams and bring every receipt I've incurred since January back to the shop along with my receipt for a 1993 90hp and demand every penny returned to me along with the market value of the 1980 90hp I traded them.

Seems like I have a pretty solid case in small claims court if I choose not to put another hour or dollar into this. Got a receipt for a 1993 90hp. Got a motor with 120/140 cylinder heads and 120/140 carbs. Got a boat that says coast guard rated max hp 90. Got lots of receipts I wouldn't have incurred had they not sold me this motor. Got details of the motor I traded them to knock off the install and shop fees for swapping this motor in. Who knows maybe with all this in front of him he will have to just yank the thing off and give me cash and avoid the trouble?

Otherwise what can I do with this thing now other than put a preposterously low pitch prop on it and go slow?

 

[nymack66]

Re: 1990 evinrude 120 4600rpm WOT enough?

I personally lobby for photos a million times over. Very few will post...They are priceless..
Your gear case is V6 and needs to be swapped out.
Your carbs clearly shows 140 hp not 120 if it was a 120hp you will not even see close to 4k rpm !
Post the numbers on the jets exactly how they are installed currently, I wanted to make sure you are jetted correctly.

 

[proaudioguy]

Re: 1990 evinrude 120 4600rpm WOT enough?

I would love to know where to get those decals or similar. My V4 had the plastic plates and they are so brittle one of them came off in my hand the other day. The 10 yo just looked at it and it broke. I also have spots where you can see the fiberglass. Do I need to have a professional refinish this thing, or can I sand it smooth and paint it white myself and expect pretty good results? Also what does "LOOPER" mean? I can't find it anywhere.

 

[archcycle]

Re: 1990 evinrude 120 4600rpm WOT enough?

I personally lobby for photos a million times over. Very few will post...They are priceless..
Your gear case is V6 and needs to be swapped out.
Your carbs clearly shows 140 hp not 120 if it was a 120hp you will not even see close to 4k rpm !
Post the numbers on the jets exactly how they are installed currently, I wanted to make sure you are jetted correctly.

Is there any reason I would have to find a 15 spline V4 lower? I would like to assume the drive shaft is the same and I could go get any 13 spline V4 lower?

 

[nymack66]

Re: 1990 evinrude 120 4600rpm WOT enough?

"Is there any reason I would have to find a 15 spline V4 lower? I would like to assume the drive shaft is the same and I could go get any 13 spline V4 lower? "
Yes I will recommend you get a V4 13 spline LU. The most important thing here is to know if you have 25" leg or 20". Post pictures of the LU anyone can tell in a jiffy.
I am more than happy to send you a 13 spline 13 x17 prop for your new LU u pay shipping or pick up.

..
As for the Decals go to ebay.com search on Evinrude Decals plenty of options.
Just sand and patch any holes, use high build epoxy primer, sand, shoot with a 2 part Epoxy polyurethane with a high UV resistant and wax, its what you are looking at.
Not to side track here ..PM me if you like .