Johnson/Evinrude : ) Questions for DHadley

[Bob_VT]

I consider you the johnnyrude guru here. So I had read in an older post you mentioned loopers vs cross flow. You stated that a cross flow 140 was 115 at the prop and loopers had more potential. Well I have a 79 85 v-4 looper and I know it was rated at the crank so what would the true rating be at the prop? Is there a rule of thumb formula? I realize that mine is the 90 cubic inch and the next step is 99 cu in...did the 9 cubic inches make that much differance?<br /><br />Bottom line I have a set of 115 carbs, manifolds and reeds that I intend to install. Since I lack the Cubic Inches I know that I will not be gatting 115 at the crank however I realize that some gain should be noticed. Comments? Will it be in theory 100 hp (splitting the differance). Should I be hunting down a bubble back exhaust plate next?<br /><br />Thanks,<br />Bob

 

[jwhite]

Re: Johnson/Evinrude : ) Questions for DHadley

You should be hunting for a bigger motor. It would cost more to get more horsepower out of it then it is worth. Just putting 115 carbs/reeds will not give a noticible difference, just burn more gas. Best thing to do is sell it and buy a bigger motor or be happy with what you have.

 

[Bob_VT]

Re: Johnson/Evinrude : ) Questions for DHadley

Yes, the bigger motor is directly related to my slowly metabolizing infection of two foot fever, just ask my Doctor ! I have the parts on hand for what I want to do now, I was curious on the end result of treatment. My Banker (not even related to my HMO) has also assured me that my current bank account will keep the two foot fever in remissision.<br /><br />If the parts were not on hand, I would not consider the attempt. <br /><br />Bob

 

[Franki]

Re: Johnson/Evinrude : ) Questions for DHadley

Maybe you should try to change the exhaust over too, makes a big difference on a two stroke...<br /><br />There is no way anyone could tell you what the result would be unless they had tried those exact changes themselves, you might even end up losing power.. only way is to make the changes and test it. (Incidently, I am personally of the opinion that lower units do not take off 10-15% of power in an outboard.. my cordless drill(12v) had no trouble spinning my lower unit at all, full speed.. lower units are not like a car drivetrain, and the losses are much less noticable on an outboard. for starters, there is no stepdown gearbox as such, and no diff.. just a couple of selectable gears for forward and reverse.. Its something to think about anyway.<br /><br />but if you get the exhaust intake and ingnition the same as the bigger motor.. and 9ci becomes the only difference between the two, then you will probably see the power you are talking about. 9ci isn't really that much..<br /><br />While you have the motor apart, you could also do the standard port matching, and maybe get your block ported and perhaps some head work done.. I have seen that result in significate HP improvments on other non outboard 2 strokes, and think it quiet possible that the same improvements would apply to outboards. There are quiet a few machine shows with people experianced in this sort of work in my area,, you could end up with more HP then the 9ci would have given you.<br /><br />just some thoughts.. but I mostly agree with the others, normally it costs more to "hot up" an outboard then it does to get a bigger one to start with..<br /><br />rgds<br /><br />Frank

 

[almost retired again]

Re: Johnson/Evinrude : ) Questions for DHadley

If there is no step down,why is the pinion gear smaller than the driven gears?<br />Just wondering

 

[Bob_VT]

Re: Johnson/Evinrude : ) Questions for DHadley

Okay I put the carb/manifold transplant on hold. I did all my other maintenance (new h2o pump, plugs, lower unit oil...)but there are still future plans for playing with this motor. I am still curious about the horsepower ratings. I wish I had a dyno....just can't justify the expense!<br /><br />Bob

 

[petryshyn]

Re: Johnson/Evinrude : ) Questions for DHadley

I'd wait for Dhadley......it might be as easy as machining the intake to a common bore, boring the cylinder ports and replacing the exhaust plate along with the carbs.......he'll know

 

[Dhadley]

Re: Johnson/Evinrude : ) Questions for DHadley

Sorry about the delay. I had to go to the Keys for a couple of days. Tough job. Anyway lets start with your model number. A '79 should be the 3.5" (vs 3 3/8") bore crossflow. But no matter. Tell us about your boat. What are you looking for? What performance do you have now? Compression? Carbs clean? What fuel, plugs, top RPM (with average load), oil and prop. What X dimension (antiventalation plate in relation to bottom of boat)?<br /><br />The guys are right. Simply bolting on bigger carbs will just most likely burn more fuel. And kill the acceleration. The goal will be to make your motor as effecient as possible. Yes there are things to do but lets establish a base line first.<br /><br />Sorry for all the questions but it's where we have to start.<br /><br />Good luck!

 

[Bob_VT]

Re: Johnson/Evinrude : ) Questions for DHadley

Thanks for the reply (wish I had that tough job ) Like I stated I put it on hold (actually due to parts) The carbs I have need to have a primer set up installed .. they are later model than my engine. I am in the process of hunting one down. I can't see installing the carbs w/o a cold start-up circuit since the larger ones do not have choke flaps.<br /><br />The boat is an older heavy (1000 lb dry unrigged)tri-hull. I guess I was looking for the proverbial "more power". I top out at 41 mph right now. The engine is the older '79 with the smaller bore at 90 ci. Like I stated earlier I do have the 115 carbs/manifold and reeds. No the hunt for the priming circuit. Seriously I might leave well enough alone and just sell the parts I have. I am still curious about the power rating at the prop? <br /><br />Thank you again,<br />Bob<br /><br />OH Yeah...by the way Almost retired again (I am once ) just to confuse matters some of the race boats step up the prop speed. This all depends on the power but 1.87:1 2.0:1 are "common" outboard ratios ...which equates to a slower prop speed than RPM's.

 

[Franki]

Re: Johnson/Evinrude : ) Questions for DHadley

Almost retired again..<br /><br />Sorry, I was incorrectly oversimplifying..<br /><br />I guess I meant to say there is no variable stepdown mechanism.. (ie different selectable gears)<br />There is nothing with the complexity of a auto type gearbox and nowhere near as many moving parts. <br />But the point I was making is still true, alot of people seem to think that an outboards gearcase will cause roughly the same HP losses as an auto drivetrain and that just isn't the case.<br /><br />rgds<br /><br />Frank

 

[Bob_VT]

Re: Johnson/Evinrude : ) Questions for DHadley

^

 

[Dhadley]

Re: Johnson/Evinrude : ) Questions for DHadley

Bob, lets start with the model number. The primer solenoid is very easy to get and all you need then are some hoses. But lets see what you have first. The 79 model 85 was the larger bore. The small bore 85 was up to 1978.<br /><br />Let us know!

 

[Bob_VT]

Re: Johnson/Evinrude : ) Questions for DHadley

DHadley Thanks again, drop me a line so we can swap e-mails and not tie up the board.<br /><br />Bob<br /><br />rpf924@hotmail.com