Upping output on '82 'Rude 90

[interalian]

Got a bead on a blown E115TLCNB (seized piston) for cheap. TNT is good, so a spare for that if nothing else would be good. Since I'm probably going to tear the 90 down in the fall, what parts would transfer that would make the extra power? Or should I try to find a 140?

 

[Chinewalker]

Best bet with what you have would be to rebuild the 115 powerhead and bolt it on the best of your lower unit stuff. A 140 would give you the exhaust tuner. The 115 has the same porting as the 140, minus the tuner.

 

[emdsapmgr]

I'd take the larger 115 carbs. Probably 1 5/16" throats. Should add quite a punch to the 90. Heads are the same as the 115. I'd pull the rubber intake filler blocks out of the 115 and transfer them to the 90. Worth 3-5 hp. The original 90/115 power packs were unlimited rpm packs. All later packs are rev limited at 5800. If the 115 has any original packs left, transfer/lkeep them for the 90. If you tear the 90 down and port it, you should wind up with a 1982 115 block. Putting these goodies on it will get you 115 crank hp. While you are installing the rubber intake filler blocks, consider adding a set of composite reeds. Even idling, good mid-range punch. Might even pick up a hundred rpm on top.

 

[interalian]

All good advice. Donor engine may have too much wrong with the powerhead to use as a rebuild candidate though, especially if the sleeve is shot. Will have to see once I can tear it apart, assuming I do get it. The parts explosion on shop2.evinrude shows the 115 had the bubble butt exhaust plate like the 140. Oh, and my 90hp has original power packs - not sure about the ones on the 115.

 

[emdsapmgr]

The 115 model plate indicates it's a 1982 also. If that's true, that engine is a flatback just like your 82 90 hp. The 115's did not get the bubble back exhaust till the 1985 model year.

 

[interalian]

True. I was looking at the picture on shop2.evinrude and it showed the bubble butt exhaust. Looking at the list showed it was for the 140 only. Either way, I think it would be fun to perk up the HP on the old girl. The tin sport boat I have used to run 44mph on a 17" screw when it was new, and I bet with another 20 or so HP it would crack 50 with a 19 or 21" screw.

Oh, and a few years back I put some transom wedge shims on the motor as it never worked properly into the low trim range. That made a huge difference in rougher water, being able to get the bow planted.

 

[emdsapmgr]

With another 20-25 hp, you will need to go up to the next size prop-for sure (19). The 140's used to come with the 21-back when OMC shipped props with the engines.

 

[interalian]

The 115 fell through - guy wasn't willing to part at my price. Got a '79 140 in sight with low compression and no spark on 3. Not sure I'd really want that much power on the 16' boat, but hmmm.

 

[1983 ercoa 21']

Back before the internet days when all this information was easily available and I didn't know very much about outboards.
I had a 80 100 rude that I put the bubble back and 115 carbs on . It really woke that motor up it would push my heavy fish and ski shaped more like a bass boat in the mid 40s .

 

[interalian]

From what I've read, the exhaust tuner gives high end at the expense of some bottom-end torque. Since this hull is only rated to 105, maybe I'd just do carbs and intake plugs? Or maybe the 140 is a better candidate for rebuild than the old 90 (which also has not the best compression), then run the 140 with a throttle limiter to keep it off full chat.

Whatever I do, I'll probably leave it with the 90 lid... :laugh:

 

[1983 ercoa 21']

Just because you have the power don't mean you have to use it! Lol
but it's there if you want it.

 

[racerone]

I have taken many of these motors apart.------The 90 hp block has smaller intake ports than the 115 / 140 hp versions.

 

[interalian]

Just because you have the power don't mean you have to use it! Lol
but it's there if you want it.

Lol. That's what I tell the wife about the turbo boost pack I run on my BMW 535xi - gives an extra 80hp and 120lb-ft at full gong (300/300 on the factory TT). Lots of fun to have a stealth machine that slips all 4 wheels on the 1-2 shift and needs the traction control OFF for launches on dry pavement - otherwise it pulls the plug on the fun.

 

[interalian]

Got the 140. And like a dog chasing a car...

This was an inland motor from Saskatchewan, so no corrosion anywhere I can see. Wiring has been hacked over time but that doesn't matter as I can use all the wiring and stuff from my '82. I have a fun winter project ahead. Anybody want to come help?

Modeling a new hat - that's still the 90 underneath.



140's cap is just nasty, but my plan has always been to use the cap off the 90.



Yup, it's a '79.

 

[1983 ercoa 21']

Looks like alot of fun. Enjoy

 

[AEROCOOK]

Cool project, I hope you can keep us updated. I'm especially interested since I also have a 16' Springbok. Mine has a 1988 110 bubble back which I understand is essentially the same as an early 80s 140, the 140 being powerhead rated and the newer 110 being prop rated. Anyhow, I plan on tearing mine down this winter to put in new rings since one hole is at 104 psi and the other 3 are at 117. I just tore apart a 1990 88 Special so I've familiarized myself with the inner workings which should help. I also have the factory manual which is essential. Keep us posted fellow "Springboker".

 

[emdsapmgr]

What makes the 140 unique is the porting, the bubble back exhaust, the exhaust rib cutout in the exhaust chest, the rubber intake stuffers, the large throat carbs and the high compression heads. I'd be looking for compression over 130 on each cylinder after overhaul. The 79 carbs have choke butterflys, so you'll have to use the 79 choke solenoid and airbox assy. Should be a great runner when you're done!

 

[Faztbullet]

As posted the 140hp is rerated to a 115hp so your only gaining about 30hp not 50hp but it will still be a good upgrade

 

[interalian]

As posted the 140hp is rerated to a 115hp so your only gaining about 30hp not 50hp but it will still be a good upgrade

True, but doesn't the '82 90hp have the same 'shaft' HP vs 'prop' HP offset? If so, we're talking apples to apples for the sake of arguement.

 

[interalian]

What makes the 140 unique is the porting, the bubble back exhaust, the exhaust rib cutout in the exhaust chest, the rubber intake stuffers, the large throat carbs and the high compression heads. I'd be looking for compression over 130 on each cylinder after overhaul. The 79 carbs have choke butterflys, so you'll have to use the 79 choke solenoid and airbox assy. Should be a great runner when you're done!

Noted. As this 140 is a freshwater motor, it'll be the preferred rebuild candidate regardless. I'm OK using a choke vs primer too, less plumbing and same electrical needs - give the choke solenoid 12V, same as primer solenoid.