Cannabalizm.. what to do

[sparkroost]

Now that I have your complete attention.. <br /><br />As some of you might know from my posts I am building a 1973 115hp evinrude wich I have added bubble exhaust and the raised 140 intake manifold. something I overlooked was the added space in the front. My air box cover will not fit. It's .820 too long and comes into place where the cowl locks down. I would have to cut the airbox and make a retro-fit or.....?????<br /><br />do they make a air filter system for this engine? Is there something I can adapt to it? I don't like the idea of no filter anyway.. so...this is my chance... If I can't do something that will look right I will change back to the shorter exhaust.

 

[OMC-ALLtheWAY]

Re: Cannabalizm.. what to do

I dont have an answer, but you might be able to help me I am building a 100V4 and This is what I have done so far Ported Reed induction m, ported Intake manifold, polished and access material smoothed out Carbs. 3/4" Carb risers will be installed next after completion, with all the porting and polishing i did I think I have raised the CFM enough to go with bigger jets it has 50s im putting in 52s, Question will the bubble exhaust manifold fit my 1980V4 100hp (as in bolt pattern), Also im going to shave the heads to raise compression ratio instead of buying older heads, Any thoughts would be greatly apreaciated<br />Thanks

 

[sparkroost]

Re: Cannabalizm.. what to do

I have no idea what engine you are running. Looper or crossflow?<br /><br />Porting the intake will not do alot. I would not advise polishing smooth as a babys butt either. The 3/4 riser you talk about will only be seen in the upper RPM range. <br />Your gain will be in a tuned exhaust and enlarged ports and or raising them. The key to a good 2 stroke is in the exhaust. The pulses need to be timed so that they coinside with the intake charge. The intake charge comes in as the exhaust is blowing out. As the exhaust exits the engine it bounces back through the exhaust and back to the ports( this is a 6th grade explanation). It can help, hinder performance, or only give you a small peek RPM range. If you had open exhaust it would actually kill low end power and you would waste fuel in the process. The frequency of the exhaust flow is where it's all at up to a certian point. You can try and pour as much fuel in as you like... but if you can't get it into the cylinder in a timed manner... you won't gain HP.<br /><br />Back to another question you had. If you have a crossflow, yes it will fit. I used a 80 something bubble exhaust on mine. I also cut the block for the exhaust as well.<br /><br />As for the heads... I am still learning on that one. I have high compression, relieved due to the fact I had the block decked. I am taking precautions so that the piston does not hit and to reduce the compression a bit. I am concerned a little, but will monitor.

 

[Hooty]

Re: Cannabalizm.. what to do

It's your deal, Sparkroost, but you don' really need a air filter on an o/b boat engine 'cause it ain't real dusty out there on the water. I've ran o/b engines w/o air filters almost for ever and no adverse effect. I don't even run a air silencer on my V6. <br /><br />c/6<br /><br />Hooty

 

[sparkroost]

Re: Cannabalizm.. what to do

Ok Hooty! Have any idea how far to go up in fuel jetting to compensate for the silencer?

 

[Dhadley]

Re: Cannabalizm.. what to do

The jetting is related to the porting and higher compression due to the block being cut, not so much the silencer cover being there or not. Remember this is a crossflow not a looper. <br /><br />OMCATW - the spacer will hurt at all rpm ranges.<br /><br />Good luck!

 

[sparkroost]

Re: Cannabalizm.. what to do

I am confused now. Adding a riser to the carbs will hinder performance at all rpm ranges? It won't help the intake charge gain velocity at higher RPM? Or is it the fact that the exhaust is not tuned for it? <br /><br />Hooty, I just looked at a link you posted with an animation of a 2 stroke looper. Very nice! I have a few articles here on tuned pipes, convergent, divergent angles. In the RC world, changing a pipe was as easy as turning a few screws and adding something that was already "proven". What makes these outboards harder is the availability of performance parts and information from the pros who have "trial and error" many blocks. It didn't take long to figure out that anyone could potentially destroy there motor with the philosophy of "bigger is better".<br /><br />In making decisions about what to do to this motor for performance, I feel a little hindered. I just don't have all the information that has been proven, or the parts. Although I want a motor that will go faster, just because, I am limited. Any of the port work I did was limited due to the fact that I didn't want to screw it up. I did make some comparisons to some other 140hp engines. Surprisingly, the port height was the same for 140 and 115 in the blocks that I found. The diameter was different, but the 140's had 6 transfer ports pr. clyinder instead of 8 in mine. I did not actually calculate the volume of the 6 ports vs. the 8, but I bet they are close in overall area. This is another reason I didn't go nutz on the porting(actually I was afraid I would screw it up to the point I couldn't fix it, or the exhaust would not be tuned for the rpm range that I wanted to use)<br /><br />After seeing what is involved in making a go faster OB motor I tend to agree with most of you veterans.... buy a bigger motor... They have done all the R&D for us. Alot of work has been done on my motor.. the last thing I want to happen is to have a poor HP producing motor, or a motor that will only perform efficiently at only a small range of RPM. Unless you want to tear it apart and have the means to measure the actual power curve each time you make a change, stick to stock, or close to it!

 

[Dhadley]

Re: Cannabalizm.. what to do

The spacers will hurt performance but velocity stacks look cool!

 

[sparkroost]

Re: Cannabalizm.. what to do

plz explain Dhadley

 

[Dhadley]

Re: Cannabalizm.. what to do

On a two stroke outboard card' motor the closer the carbs are to the reeds - the stronger the signal (base compression) will be. The stronger the signal equals more incoming fuel charge.

 

[SCO]

Re: Cannabalizm.. what to do

Sounds like the velocity stacks hinder the actual volume of air aspirated by the engine. Is that correct? Sorry to butt in, but want to stay with the discussion. Are you supposed to scoop air into these things at speed?

 

[OMC-ALLtheWAY]

Re: Cannabalizm.. what to do

Ahh, scratch the spacers. Thats ok cause now I dont have to finish making them, Ditto on the polished aluminum looking cool though. I did not polish any thing but the carb venturies to try to get enough flow to go to bigger jets, I thought the roughness of the intakes helped atomize the fuel. All I did was remove Casting inperfections. I have someone comeing over tonight with old heads to see if they fit if not its to the Mill and Fly cutter. Next week im ordering boysen reeds. , Now can I just polish the exhaust to gain flow without hurting the expansion chamber type affect?????. One more thing My freind has a 98cc 2 stroke putting out 14hp he claimes due to the awsome, huge and cool xpansion cahamber, he talks about the supercharging affect, anyway this makes me think, are our outboards even using this philosiphy, I mean a 2cy 300cc makes only around what 8hp. Any thoughts? and also I hear you about the bigger motor thing but im haveing soooo much fun building this sucker.

 

[OMC-ALLtheWAY]

Re: Cannabalizm.. what to do

Ahh, scratch the spacers. Thats ok cause now I dont have to finish making them, Ditto on the polished aluminum looking cool though. I did not polish any thing but the carb venturies to try to get enough flow to go to bigger jets, I thought the roughness of the intakes helped atomize the fuel. All I did was remove Casting inperfections. I have someone comeing over tonight with old heads to see if they fit if not its to the Mill and Fly cutter. Next week im ordering boysen reeds. , Now can I just polish the exhaust to gain flow without hurting the expansion chamber type affect?????. One more thing My freind has a 98cc 2 stroke putting out 14hp he claimes due to the awsome, huge and cool xpansion cahamber, he talks about the supercharging affect, anyway this makes me think, are our outboards even using this philosiphy, I mean a 2cy 300cc makes only around what 8hp. Any thoughts? and also I hear you about the bigger motor thing but im haveing soooo much fun building this sucker.

 

[jim dozier]

Re: Cannabalizm.. what to do

No doubt that awesome 14 hp comes on like a hammer in a powerband peak of about 10 rpm at 10,000 rpm. At 1,500 rpm he's got nothin.

 

[OMC-ALLtheWAY]

Re: Cannabalizm.. what to do

I also have no idea what it is Lopper-Crossflow how can you tell.,Can you please tell me. The back of motor between the heads is flat if that means anything. And also what years did they have the fancy exhaust and what hp where they on. The kids 98cc W.O.T is 14,000rpm and yes it has a tight powerband with top end gearing you have to push the gocart or it will stall but once its rolling zoom 60mph, scary I wont even ride th SOB with acceleration gears and fancy clutch its outa the whole like a drag car (spinning wheels and all) and 40mph in seconds, This is kinda irrelivant but its cool to talk about.

 

[sparkroost]

Re: Cannabalizm.. what to do

Welp... it's getting closer to the bottom line! I am pulling the old motor this morning and installing the old one(he he). I still have alot to do.<br /><br />OMC, as for polishing the exhaust....I don't think it's worth it, the effort anyway. Lots of carbon buildup. In no time it will become nasty. I just did like you.. removed the high casting marks, made a little room for exhaust to flow and that's it. I am trying to keep the integrity of the engine so that if I decide to sell her she will not be butchered up. All the changes I have done are as close to stock 135 as I can get without making too many permanent alterations. If I get 125-130hp I will be happy!<br /><br />Ditto on the enjoyment of this process. It has been very time consuming though and I am ready to see the results. If Betsy doesn't perform to expectations I may remove her and make a few changes. So far things are looking well.<br /><br />I am having some trouble with the throttle shafts. Is it possible to buy bushings for the shaft or will I have to make them myself? OMC sure made that shaft long where the throttle cam is. Puts alot of stress on that outter bushing and is prone to wear.<br /><br />OMC, I should have this girl in the water Sunday and broke in by next weekend. I will let you know what I did and how the results were.<br /><br />I can't emphasize how thankfull I am for all the information I have gotten here. Thank you all.

 

[Dhadley]

Re: Cannabalizm.. what to do

What kind of rpm are you guys looking for?

 

[sparkroost]

Re: Cannabalizm.. what to do

7000

 

[Dhadley]

Re: Cannabalizm.. what to do

Not a problem. We did that in classes that all you could do was bore the block to +.030. No porting, no grinding, no removing metal from the block, crank, pistons or rods. We used stock uncut heads too.

 

[sparkroost]

Re: Cannabalizm.. what to do

ok, I want more, he he<br /><br />How much can I get with slight mods like the ones I have done... Safely... cratering is not on my list for this engine.<br /><br />Intake stuffers with 140 intake(.820 longer)<br />.020 over forged weisco<br />high comp. heads, slightly relieved, surfaced<br />block decked .005<br />bubble exhaust, cut block, no tuner manifold inside(kinda wish I woulda done that but was stated I didn't need it... we shall see!)<br />1 3/8" carbs<br />boysen reeds( have not bought yet, waiting on setting up engine before purchase and install)