Need more HP 90/115/140

[StratosRob]

Can anyone tell the the diffrence between 90/115/140 I was told it was only the carbs. I need a little more giddy up with out having to buy a new motor or rig. Right now I have a 1989 90 V4 VRO. Could I take this motor and turn it into a 115 or maybe even a 140 . Thanks

 

[kenmyfam]

Re: Need more HP 90/115/140

I can not answer your question but my thoughts are that making a 90hp into a 140hp by just changing the carbs and pouring more fuel into it is not feasable.
The experts on this will be along I am sure and tell you the true reality. I will be watching this with interest so I can learn about this also. My 140hp is a 1.8 litre if that is any help.

 

[throwback2332]

Re: Need more HP 90/115/140

Heads i belive

 

[WillyBWright]

Re: Need more HP 90/115/140

With a little work (far more than just carbs) you can turn a 90 into a 115 or a 120 into a 140. But you can't turn a 90 into a 140. The internal configurations are completely different. Different pistons, different cylinder porting, different heads, more.

 

[tashasdaddy]

Re: Need more HP 90/115/140

go here and compare parts. http://www.evinrude.com/en-US/Accessories/Literature/

 

[StratosRob]

Re: Need more HP 90/115/140

Ok here is a start lets say I want to go from a 90 to a 115. Bigger carbs for sure,(115) what else is involved.140 would be nice but didnt think so.
Thanks for the replys everyone

 

[gotboostedvr6]

Re: Need more HP 90/115/140

all V-4 motors of the same year have the same crank rods and pistons

What they dont share are heads, carbs, reeds, exhaust tuners and plates, flat back or bubble exhaust, and port timing/ port size.

you can make a 85 hp a 140 with a die grinder and some new parts

 

[WillyBWright]

Re: Need more HP 90/115/140

Same cranks and rods, yes. Same pistons, no. 85s to 115s are crossflows and 120s to 140s are loopers.

 

[emdsapmgr]

Re: Need more HP 90/115/140

The 140 block has high ports, your 90 has low ports. This you can't change. Also, the 140 (and later 115's) have the bubble back performance exhaust. While you can add this to yours with some machining, it is not worth it for a 90. You have low compression heads now. What you can do to improve: 1. add a set of 81 or earlier 135/140 heads. This will boost your compression. 2. add the larger 1 5/16" throat carbs. This will flow more fuel and air= more horsepower. You will need watch the choke setups on new carbs. 3. You can add the 4 intake filler blocks (NLA-but you can find them around.) They will add a few hp. Part # 322684. When you have the intake off, consider composite reeds-they help at idle and throttle response. All of these parts bolt on. You will notice a significant difference. Your engine has the single power pack, with a built in rev limiter, perhaps at 5850. The older engines revved higher, with double unlimited packs.

 

[jimmbo]

Re: Need more HP 90/115/140

Same cranks and rods, yes. Same pistons, no. 85s to 115s are crossflows and 120s to 140s are loopers.

wrong

1977 thru 1984 99.6 cu.in. crossflow 140hp



A 90 can be changed in to a 140. Block has to be ported to match the porting on the 115/140 block. Pistons are the same. The heads are different. The bubbleback and exhaust stuffers will need to be added and this will require some machining of the block to do so. Also required will be the exhaust tuner(megaphone) 1977 version is the best. The carbs will have to be changed( 78 and 79 140s had the largest cars 1 3/8 inch). Optional are the rubber intake stuffers neear the reed valves( some 140s had them other didn't ).

 

[StratosRob]

Re: Need more HP 90/115/140

I knew you guys would'nt let me down. Ok so let me get this right put 81 or earlier 135/140 heads.= raised compression. Install 1 5/16" carbs = more air and more fuel.= more HP. Do I have to change the power pack or can I keep mine? I dont want to over rev. the engine. Do I keep the same intake and reeds for the bigger carbs or do I need 135/140 intake and reeds? I'm not interested in making any modifacations to the block. To everyone thanks for any input.

 

[Silvertip]

Re: Need more HP 90/115/140

This question gets asked time and time again and the answer is always the same. If you need 140 HP, buy 140 HP. Every manufacturer makes two, three, and sometimes four engines with the same displacement. Unless you have access to a salvage yard or a junk engine with the parts you need, these conversions with few exceptions, are rarely worth the effort from a cost standpoint. You may even run into lower unit gear ratio issues even if you do find the necessary parts. That could negate the advantage of increased horsepower.

 

[Dhadley]

Re: Need more HP 90/115/140

You need to start with the basics. Tell us where you are now with the 90. If you haven't maxed out the set up now, you may actually lose by installing larger carbs. If you're at 6000 or more now larger carbs may help. Larger carbs will, generally speaking, have less acceleration but more top end. Smaller carbs will have more acceleration and a little less top end.

If you're at 5500 now, larger carbs will hurt performance.

Regardless of what you do you'll still have the same bore, stroke, ignition, intake, tuner and gear ratio. You can make your 90 create a little more torque but not much. You can turn it into a 1989 115 (crossflow and same as a 1984 140) but not a 1989 140 (looper).

Your boat will have to be very sensative to small increases in torque. Let's find out where you are now before you spend a lot of money.

Increasing performance is like taking a trip. You have to know where you're at now and where you want to be so you can chose the best route to take.

 

[StratosRob]

Re: Need more HP 90/115/140

Well this is more like a project. Just to acumilate the parts I may need. To do the upgrade. If I need a 140 then buy a 140 well its just not that easy. Maybe for you but not for me.I have to buy a little here and a little there. I'll have to remember that. I must buy what I need not make it. Thanks for the TIP !

 

[emdsapmgr]

Re: Need more HP 90/115/140

Use your same intake and reeds. Ditto for the ignition system.

 

[gotboostedvr6]

Re: Need more HP 90/115/140

Here are some of the things you need to mod on a crossflow thats less then 140 to increase HP:
You need the tuned exhaust housing and 140 carbs [carb are 1 3/8 vs 1 1/8-+]. the hard part is finding what is called the filler blocks. They are wedged shaped blocks that made a flat surface for the tuned exhaust to mount to. The 135 and 140hp motas all had the blocks. OMC would never sell them as a part. The difference between the 135 and 140 is a 1" gap in the center web under the tuned exhaust. Only the 78-79 140's had the 1-3/8 carbs all others had 1-5/16. The 85, 90, and 100 hp V-4's had even smaller carbs

A little cross flow V4 history:

Starting with the 1973 135hp V4, basically the first motor to offer performance using things learned from the racing programs KC and KR engines.
The 73 135 is a unique year using different internal engine parts than the later motors but stock performance is about the same as the other years. Hottest head on a production V4
The 1974-76 135hp changed the internal engine parts to be very similar to the later model engines. Slightly Looser heads than the 73.
1977 was the first year of the 140. Better gear case design all though still hydro mechanical shifting. Internal rams on the Trim and tilt, Different exhaust tuning. Slightly looser heads again, some had coil mounts but the ones I have seen were not tapped.
1978-79 140s are thought to be the strongest of the 140 in stock form because they had 1 3/8 carbs stock. The exhaust system changed again to what was used for the rest of the V4 Xflows built. Heads are the same as the 77 140 with coil mounts.
1980-84 140s were back to the 1 5/16 carbs, some had intake stuffers, some didn’t. Heads were slightly looser again from the 78-79 heads but great for pump fuel and easy to find.
In 1985 all OMC Engines were changed to the prop shaft rating. The 140s became 110hp. Along with power head to prop shaft ratings the heads went very soft. Known as the Bathtub heads.
I believe in 1990 the 110 became a 115 along with the SLP models being a 112. Built until at least 1998.
Basically the same as the 1980-84 140s with soft heads and no intake stuffers.

 

[gotboostedvr6]

Re: Need more HP 90/115/140

Adding finger ports to a cross flow help it breath, keep it cool and helps overall combustion.
Here is a properly placed finger port:

Finger ports on a OMC Looper help scavenging through the bottom and mid range of the power band and are essential to making good power on these motors.
On a Cross-flow OMC they are more for reliability. The design of a Cross flow piston holds allot of heat in the dome especially when held at WOT For longer periods of time in proper tune. The finger ports in a Cross-flow help to move a cool intake charge under the piston and wrist pin bearing area. An area where not allot of flow takes place at high RPM’s. While they help a small bit with power if done right they are essential in an Xflow for reliability such as ModVP or endurance racing.

Finger ports pull the charge out from underneath the piston crown, thus keeping the dome cooler. Also, cleaning out the charge in the case, which helps the engine pull more volume. They should be higher than the transfer ports, but not higher than the boost port. A little lower than the boost port actually. And as far as not putting them to close to the ring gap, well its not like you will put them between the transfer and the exhaust. They should be right on the ring gap.

 

[gotboostedvr6]

Re: Need more HP 90/115/140

Keep in mind this info is for crossflows only

one more thing the port timing is way different from a 90 to a 140 a dremel and a good bit can make quick work of the differences.....

V-6 pistons and rods of the same bore and stroke are lighter and stronger then there v4 counterparts they can hold 10% or so more rpm

 

[Dhadley]

Re: Need more HP 90/115/140

"the hard part is finding what is called the filler blocks. They are wedged shaped blocks that made a flat surface for the tuned exhaust to mount to. The 135 and 140hp motas all had the blocks. OMC would never sell them as a part."

FYI -- The exhaust filler block kit is part number 392000 although you don't need them to install the bubble back exhaust manifold and water jacket.

 

[Rudy Brown]

Re: Need more HP 90/115/140

Man, this is some great info posted here. But I still think I'm gonna just go with a looper 150 v6 on my boat when I upgrade.