1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

[CaneCutter79]

From what I can tell, these two outboards use the same powerhead. What's the main difference between these two motors? How does one get more hp than the other motor? Can any of you more experienced folks help?

 

[CaneCutter79]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

I checked the part numbers just now for carb assembly and powerhead. Both the 85hp and 115hp motor are the same.

So where is the HP difference? How can one motor have that much more power rating than the other motor? Gearing? Is it easy to convert one to the other? Or not worth the trouble?

 

[durban]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

i dont know what they did in the factory , but every thing is the same even the piston , cranksharft , block, carbs , gearbox & gears , pump , electrical & so the list goes on & on

the only differance in the 2 is the price on the block & intake manifold the 85hp sells for over 3, 000 dlrs & the 115hp 2,000 & something so this what it is , maybe they used some special way of casting in the 2 , & have to make money some how . cheers

 

[durban]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

I checked the part numbers just now for carb assembly and powerhead. Both the 85hp and 115hp motor are the same.

So where is the HP difference? How can one motor have that much more power rating than the other motor? Gearing? Is it easy to convert one to the other? Or not worth the trouble?

the easiest & fastest way to do a conversion on these 2 motors 1979 in the R SERIES Is just change the top cowling covers over then you have one day a 85hp & the next day a 115hp

 

[Faztbullet]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

The 85 hp block has smaller exhaust ports, say the size of your pinky and the 115hp has exhaust ports the size of your thumb. The carbs are different as the 85hp usually uses a 1-1/16 bore and the 115hp a 1-3/16 bore.

 

[durban]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

funny enough the carb complete on both motors , part no the same , so your gess is as good as mine

 

[emdsapmgr]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

Fastbullet has the correct info. The 85 hp crankcase is not the same part number as the 100/115 or the 140 block. The carbs can't be the same part number as the throats on the 115 carb are much larger than the 85. They all use different jets. The 115 and 140 both use the rubber intake filler blocks (322684) which is good for 3-5 hp. If you want some simple improvements, locate a set of 1 5/16" throated carbs from an older 135. They'll bolt right on. Add those intake filler blocks. If you want to pull the powerhead down, you can square off the intake and exhaust ports for better breathing. I've done these mods to my 79 85 hp engine and it really improved the performance. The heads that are stock on an 85/100/115 will put out 125 lbs compression-decent. You could change them out for a set of 140 heads from that year for another 10 lbs or so. A set of composite reeds makes for nice idling and improved midrange. You may even pickup a couple hundred rpm's on top end. You can compare the parts differences on the Bombardier website: epc.brp.com

 

[CaneCutter79]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

I found the difference!!!!!!!!!

After looking at the part numbers side-by-side, I finally found the differences. I knew it had to be either by gearing, intake, exhaust, block, or carb assembly. It's the carb assemblies! The 85, 100, 115, and 140 are the EXACT same motors except for the carb assemblies. The individual parts for the carbs are how they adjust horsepower rating. Add a larger carb and you get more horsepower.

AFter reading some of the info above, you say the exhaust ports are larger and the blocks are different? That's not what Evinrude's parts website shows. They give the same part numbers. Can you expand a little?

I'm looking for easy bolt on power if that's even possible. If it's not, it's not worth it. I'd just assume keep the motor as is and not risk messing up something.

 

[CaneCutter79]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

If you want to pull the powerhead down, you can square off the intake and exhaust ports for better breathing. I've done these mods to my 79 85 hp engine and it really improved the performance. The heads that are stock on an 85/100/115 will put out 125 lbs compression-decent. You could change them out for a set of 140 heads from that year for another 10 lbs or so. A set of composite reeds makes for nice idling and improved midrange. You may even pickup a couple hundred rpm's on top end. You can compare the parts differences on the Bombardier website: epc.brp.com

I'm about to do a full rebuild/teardown anyway so if I can throw in some extra parts and have the machine shop rebuild the powerhead to fit a 140 or a 115, that would be great.

You say you have done this with you motor? You only increased a few hundred RPM on the top end? How is the performance better? The hp difference alone should make me have to change props I would think. I run a 17-pitch Turbo prop (3-blade) currently at 5,000rpm at 38mph GPS. If I went to a 140hp outboard, it should run significantly stronger and faster right? Thus needing a new prop with higher pitch right?

 

[emdsapmgr]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

I never baselined the original 85. Had a bad hole when I bought it. Went right to .030 overbore and did the port squaring off at that time. I've done the 135 carbs and the intake stuffers. Original heads still. The engine is pretty docile till you crack the throttle-then it hauls right from a dead stop. I have a set of 140 heads, but it runs so well, I have not installed them. It's on my daughter's boat so it does not see much high rpm, so don't have any composite reeds in it, but they are worth the $-esp if you plan on having the engine down for overhaul. Here is a pic of the porting.

 

[CaneCutter79]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

So the heads are different then? Evinrudes parts numbers for the exhaust and powerhead assemblies and parts that I saw are ident
Thank you for your information and assistance! I love my little motor and I'm willing to spend the cash to get her up and running

 

[CaneCutter79]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

Can you offer any insight to the performance of your current setup? Prop size, etc? I am curious. I run a little 15ft heavy fiberglass trihull fish/ski boat. Original motor and in terrific condition. Mine runs about 38mph now. I'd love to squeeze a few more hundred rpm out of it. It runs 5,000 rpm now and I'd like to get it up to 5,300-5,500 Max. Just a little more to keep the motor clean from carbon and to Max the performance a little more.

Its a great little motor! Hole shot is about 3.5-4 seconds currently which is incredible. I can haul full load or no load and it will run same speed.

 

[Faztbullet]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

hat's not what Evinrude's parts website shows. They give the same part numbers. Can you expand a little?

Dont know what site your looking at but the 85hpo block is part#0389912 and the 115 is part #0389606
http://shop2.evinrude.com/Index.aspx?s1=6gs8kimuba5ign1k892lfmujg3&catalog_id=0&siteid=1

 

[durban]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

you are right faztbullet , from what i can see is that the only differance in these motors iam refering to the R series is the block , as they are different part no,s proboably due to the ports , the carbs are listed the same the intake manifold the same , the reed valves 100 hp s series 115hp r series 140hp r series & 85hp , even the prices are the same that they sell for , now i dont know if your agent has got them listed at different part no , , because thats one way of makeing money selling a 85hp carb @ x amount , then the same carb because its a 140hp selling for more , due to the fact just because its 140hp , jet they are the same carbs , now tom **** & harry can get caught out like this , its called marketing biusness .

 

[CaneCutter79]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

Dont know what site your looking at but the 85hpo block is part#0389912 and the 115 is part #0389606
http://shop2.evinrude.com/Index.aspx?s1=6gs8kimuba5ign1k892lfmujg3&catalog_id=0&siteid=1

Its not the website, it's my eyes. I'm blind. The part numbers for the 115 and 140 were directly below the 85. I just didn't see them.

So you used a 135hp carb assembly on your 85? Why not a 115 carb assembly? Also, does the machine shop have to modify the block to adapt the 115 carb assembly? Or do I need to find a 135hp carb assembly as you did and use the intake filler block as you did? Which is easier and cheaper? Also, what year model 135hp?

 

[CaneCutter79]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?


So what does the filler block do and how would adding it add a few extra horses? Can you explain? This is really interestings.

SO it appears I would need to change out the powerhead and lots of other things. I'm going to try the larger carb and filler block and enlarge the exhaust ports a bit at the most. Again, thank you very much for your help!

 

[durban]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

i would just make the ports to 140 hp , put 1976 135 hp carbs on & leave the intake manifold it will bolt striaght on , & your away

 

[emdsapmgr]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

The rubber intake filler blocks take up crankcase space. They nest behind the reed boxes. The less space you have in the intake side of the block, the more velocity you get on the air/fuel coming from through the reeds. That equals more hp. All the early hi perf 140 crossflows and some 115's had those filler blocks. The V6 engines had similar ones on the hi perf 200 and 235's. Any 135 carbs will work, as long as they are from the same year. Mine were 1974's. The difference in the carbs is not so much how they look (all look the same.) The difference is in the throat size. OMC cast the identifying throat size on the face flange of each carb. Look for 1, 1 3/16, 1 5/16, 1 3/8. That's inches of throat size. The larger the size, the more fuel/air they will flow.

 

[CaneCutter79]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

So how do the composite reeds help over the standard reeds?

Also, the 115 carbs are not able to bolt on like the 135?
And since the new Carb will flow more fuel, it will burn more fuel on top end right?

And last question, how do you get more exhaust flow? Change the exhaust ports or what?


You're getting me excited and I can't wait to get the motor back! I bet it runs better than ever.

 

[bishopcherrycoke]

Re: 1979 Evinrude - Main difference between 85hp and 115hp crossflow engines?

I'd like to chime in here if this thread isn't already dead! I am in the same boat here ( I'm funny) I have a 1979 85hp cross flow I'm planning on modding once I finish the floor and transom of the boat. One difference I've found that I didn't see on this thread is the bigger cross flows had different exhaust manifolds. The bubble back cover. I'm assuming it allows better flow.

Is it wise to open up the intake ports or just the exhaust ports?