best combo???

[overkill131313]

I blew up my 1983 Evinrude 140 (crossflow).....
I just bought a 1980 Evinrude 115 (crossflow).....

my question is (and no guessing) who has made one engine of these 2? should I change heads, carbs, exhaust? anything else? Im just putting the 115 powerhead on the 140 leg....but I want to get as much as I can with the combination....I know the ports are slightly lower in the 140 but what will give me the most HP and any little secretes to get more power out of these engines with out killing it?

[EMDSAPMGR]

Swap the 140 heads onto the 115. Along with the 4 rubber intake crankcase stuffers. p/n 322684. Good for 3-5 hp. Also, swap the carbs-likely they are larger. You may need to rejet the mains slightly if the carbs overfuel the 115. Should be a good runner. I'd double check the power packs. Around the 81-83 timeframe, OMC discontinued their V4 unlimited packs. Al newer ones are limited to 5800 rpm's as indicated on the 5800 stamped on the side of the pack.

[overkill131313]

Swap the 140 heads onto the 115. Along with the 4 rubber intake crankcase stuffers. p/n 322684. Good for 3-5 hp. Also, swap the carbs-likely they are larger. You may need to rejet the mains slightly if the carbs overfuel the 115. Should be a good runner. I'd double check the power packs. Around the 81-83 timeframe, OMC discontinued their V4 unlimited packs. Al newer ones are limited to 5800 rpm's as indicated on the 5800 stamped on the side of the pack.

What do I do with the exhaust? I ask cause some guys say machining is needed on some exhaust deflectors in the "bubble" back exhaust. As for the power pac, the 1980 should not have a 5800 rev limiter but the 83 should. What one is better? Do they have a different "tune" or the same? I really don't want to spend money on this engine cause I really want to hang a 225 on the back of my CVX-16 when I redo the transom and add the braces! Just looking for the best "bang for the buck" to get me by! Lol.

[EMDSAPMGR]

When the factory installed the bubble back exhaust, they added the exhaust filler blocks. Must be some reason why they opted for all the extra machining to include the deflectors and to mill the block face flat. That might include the removal of the cooling rib at to bottom of the block, too: Found on the 140 blocks. You'll find extra performance-just using those bolt-on parts. If you want to do machining-to do the exhaust, plan on tearing the block all the way down. When/if you do take the block down, might as well port the intake and exhaust ports, too. Not sure just how much effort you want to put into this upgrade.

[overkill131313]

bummer night.....I got the 115 running and warm and did a compression test.....all good except for the top right cylinder 125, 125....90,120.....WTF this is now the 4th engine I have seen with that cylinder low......85, 2-115 and my 140.....this thing runs so smooth I thought it was great till I did the test.....I think im going to run it this way till I rebuild my 140 and look for a 225....lol Im going to put some oil in the cylinder to confirm if its rings.....It just might be a head gasket.....lol I have a bore scope but cant see much! lol any thoughts?

[EMDSAPMGR]

At this point, you'd be lucky if it was just a bad head gasket. Easy to replace and relatively inexpensive. Pull the head and check the upper seal ring on it. At that point you will get a a good visual on the top cylinder and piston. Esp, move the piston slightly in the cylinder and try to determine if the top ring is still in one pc. A flashlight may be helpful here. These engines have a history of going through the top ring on pistons, once the engine gets old and it starts to accumulate carbon around the ringsets on the pistons.

[perfmarine1]

Just rebuild and mod the 140 and be done with it. By the time you start switching parts around you could have redone the 140.

[Fuzzbutt]

The 140 I just rebuilt had good compression on all but one cylinder too but upon removal of the pistons all but 1 piston had broken rings. The low cylinder shredded one but still made 90 with the bottom ring only.

I too have it on a CVX16 and the power level is awesome. Why a 225? That's a lot of extra weight. I'd rebuild the 140. Set it on a jack plate and get enough prop for it. I'm spinning my 13.75x23 SRX to almost 6000 RPM after the break in. My motor is running wesico's 3.560 pistons and the CCMS sport reeds and I jetted the mains up to 68C's. A good friend is running a 150 eTec on his and sees mid 60's with ease. That's pretty darn fast.

[overkill131313]

ya I guess I wanted to go big or go home.....if people say it cant be done....I do it! lol long story short I love my speed! I just did 152mph in a 35 foot and got the bug! next week Im going in a 31 that does 182 so I figure 80 would be so cool to hit in the CVX-16 lol this winter I have to cut the boat in half and do the transom so I figure I will add the braces and go big power. maybe I will try modding the 140 and go with a jack plate and a big prop and see what kind of numbers I can hit.....what is the biggest hp a V-4 can get....but not go crazy and have to run race fuel? I have had turbos on sled and my cars (Grand Nationals) but has anyone played with turbos on an outboard??? water in the exhaust kinda makes it tuff but is there a way around this or a small super charger? ya kinda off topic now! lol if I could hit 60 with a slightly modded V-4, jack plate and a 23" prop I would be happy but an honest 60.....not 60.1 with just me and 5 gallons of fuel! lol

[overkill131313]

well I went out with the 115 on sat and found my speed base line.....42.2 with full tank (18g front) and full spare 5 gallon in the back...2 people in the boat, engine sitting lowest on the transom with a 19p SS prop....and 5300 RPM. Then I went home and put the 140 exhaust on.....it was bugging me to see what the difference would be..... this was not a bolt on....lol I had to tap all the holes for the alum filler pieces and check the measurement to make sure they were low enough to work properly...so the exhaust is all 140 but there is no milling of the cooling rib to split the exhaust at the bottom of the block..........so just exhaust change speed to 44.7 mph, and raised the RPM to 5450...Im going to now lift the engine up on the transom and see what the difference is.....then carbs but the 115 has 1 3/8" carbs and for some reason I think the 140 is the same but cant remember...what are the rubber crank stuffers? is this a 140 thing that is not on the 115?.....then I will change the heads.....but I want to do every single mod separate and make a note of exact change in speed and RPM.....I should really lighten up the front tank and only use the rear but I want to know true speed when I put the boat in the lake ready to ride for the day! lol all speeds and RPM are done with a Rino GPS and a digital RPM gauge.....I want to have no issues with exact numbers.....lol I would love to try a 21 or 22 Raker prop but I will wait to buy one after I rebuild the 140 totally this winter.....Im just trying to see what the most this 1980 115 can do with one cylinder low (brokin top ring and compression at 95) I should also check the timing.....seems to caugh on a idle a slight bight just off idle.....might be getting to much timing right at the start because I know carbs are clean since I just went through them......I put a new progressive 15p stilleto SS prop on to see what the speed did....being a progressive prop at 15 means its a 13 to start and ends up at a 17 in the top end.....so before the exhaust was done when I was running 42.2 mph at 5300 rpm with the 19p SS the speed changed to 39.9 mph and RPM went up to 5550.....but the boat jumped out of the water like it got another 100 HP lol But all testing is done with the 19SS with the 42.2 baseline. I will be writing down all changes to speed and RPM as I do any mod!

[EMDSAPMGR]

Both your 115 and 140 should have the rubber intake filler blocks, based on the factory parts diagrams.

[olboatman]

Scribed. Gary

[overkill131313]

Both your 115 and 140 should have the rubber intake filler blocks, based on the factory parts diagrams.

Anyway of telling what diameter the 140 carbs are? They have a different part number but that could be cause of different jets. My 115 has 1 3/8" bore.

[evilrude 1]

1 3/8 are the largest made for any crossflow and should be stamped on the face of the carb. I would think 1 5/16 for the 140 depending.

[EMDSAPMGR]

Some of the early 140's used 1 3/8" carbs. You will have to check the face casting flange on the carbs to see what size the throats are.

[overkill131313]

so I ran the 115 on the lake and it ran ok for a low cylinder.....I cam home and put on the 140 bubble exhaust (not a bolt on...lol..I had to drill and tap the holes that hold the filler blocks....) so the exact combo I got 2.4-2.5 MPH (on GPS)more and 200 RPM more....but long story short the back of my boat now needs a new transom.....I think I have a winter project...lol but yes the exhaust helped....but I hope I can rebuild the 140 this winter and since I also have a 115 and a friends 115 all sitting on the bench now.....looks like I get to do all 3 now....wonder if I can get a discount rate at the machine shop for boring since set up is the same for all 3 blocks...lol

[olboatman]

so I ran the 115 on the lake and it ran ok for a low cylinder.....I cam home and put on the 140 bubble exhaust (not a bolt on...lol..I had to drill and tap the holes that hold the filler blocks....) so the exact combo I got 2.4-2.5 MPH (on GPS)more and 200 RPM more....but long story short the back of my boat now needs a new transom.....I think I have a winter project...lol but yes the exhaust helped....but I hope I can rebuild the 140 this winter and since I also have a 115 and a friends 115 all sitting on the bench now.....looks like I get to do all 3 now....wonder if I can get a discount rate at the machine shop for boring since set up is the same for all 3 blocks...lol

Great post! :thumbsup:Shows how important exhaust flow is in an outboard (any combustion engine for that matter) and OMC saw a weak point and dealt with it. JMO:) Gary

[omcforever]

Yep,,the bubble back is good. My 1994 115 with re-jetted 1 5/16 carbs with early 80's 140 heads runs great. Just gotta watch the timing and octane...LOL . Good luck on the transom.