115 to 140

[fishlips]

I was just in the Keys with my 1998 EV 115 SPL OB motor and had a great time down there.

This motor is wonderful, reliable and strong. I bought the boat, motor and trailer last fall used off a private roadside seller. The owner loved to fish and had a heart attack, fell off the boat and his son in Iraq sold the boat through a friend who knew nothing about the boat & set up. But when you get 4 people in the boat it is slow. I scuba dive too so weight effects the performance at this displacement and horsepower just a bit too much. I could use the extra 30 HP

Anyway, while down there for a week vacation, I met a mechanic in the Keys that has been doing engine failure analysis and repairs down there for 30 years. He worked on my boat. I had broke a shifter cable so we replaced them. He was a great guy and unfortunately I don't live down there to do this work with him. He is available by phone but I need to find the carbs first and then I can do the mechanical provided the right carbs are obtained ...but:

Here is what he said: " if you get a set of 140 carbs for your 115 engine they will bolt right on, linkages and all but you must get either 1982-84 140HP crossflow carbs. Since you currently have a 1998 bubble back 115HP, they will bolt right on with no other modifications. I've done this conversion several times and know others who have successfully done this as well."

The issue is that I went to buy the brand new carbs for those years, they are available but the factory tech backed away due to gov regs and wouldn't/couldn't help me. He did not deny that it could be done but directed me here to this particular forum to get some help. Also, he may not have been aware of the unique years and fitting/matching carbs that can work in my situation.

Sure I would love an ETec 175 (the max HP the boat will handle), maybe one day I will get one, but I cannot afford that for a few years.

I would really like to engage a technical conversation of the feasability, a second educated opinion about this conversion, hopefully avoiding all the philosophers, to learn what carbs to buy or if anyone has a legitimate second opinion having tried and failed or succeeded in doing this conversion.

[EMDSAPMGR]

The 1998 115 crossflow is actually the propshaft rated version of the old 140 which was crank rated. You won't see much difference between the performance of the two. Your 115 should already has the larger 1 5/16" carbs and the bubble back exhaust. If you wanted some small gains, I'd add the rubber intake filler blocks from the old 140 and a set of 1979 140 crossflow heads. Adding composite reeds when you have the intake off will be another plus. If you add the tighter heads, I'd be concerned about running lean-you may need to increase the high speed jet sizes slightly. You won't see a 30 hp gain, but you should see a slight perf. gain.

[delawarerick]

For what you doing and the weight you are hauling I would leave it alone. You are not gonna gain enough for it to be worth messing with. Save your money and get a larger engine. As long as you dont lug the engine and keep good fuel and oil it should hold up and look for a v-6. .02 Rick

[fishlips]

The 1998 115 crossflow is actually the propshaft rated version of the old 140 which was crank rated. You won't see much difference between the performance of the two. Your 115 should already has the larger 1 5/16" carbs and the bubble back exhaust. If you wanted some small gains, I'd add the rubber intake filler blocks from the old 140 and a set of 1979 140 crossflow heads. Adding composite reeds when you have the intake off will be another plus. If you add the tighter heads, I'd be concerned about running lean-you may need to increase the high speed jet sizes slightly. You won't see a 30 hp gain, but you should see a slight perf. gain.

Thanx for the replys. Might I ask some questions to help me understand a little better?

1) "Crank rated" means the HP rating of the old 140 was liberal (like rating an auto engine at the crank shaft rather than at the tire/road?) and now the newer (mine) 115's are prop/shaft rated...keeping them more in reality with what hits the water? So if you crank rated my 115 it might be a 130 or something by that means of establishing HP?

2) So my carbs are the same bore as the intakes they are bolted too? This was what was explained to me, perhaps in error...that my current 115 carbs are smaller in diameter than the openings on the intakes they bolt too, which were made to accept larger 140 carbs. This is either true or not I guess. So 1982-84 140hp carbs are 1 5/16"s? Interesting.

3) "Rubber intake filler blocks". Is it their composition (rubber) or the design of them? What do they do or contribute for the HP?

4) What is the specific difference in the heads between a 1979 crossflow 140 and my 98 115? "Tighter" means shaved to get more compression or something? Would milling my heads do the same thing or are there other design things that only the 78's can provide?

5) Composite reeds. If you wouldn't mind explaining these to me. Seems like valves that are made with another material than steel?

Now I owned an auto shop for 10 years back during the 80's. I appreciate the reality dose from your posts and would really rather get something like an Etec 175 for my boat perhaps. I think I will do that someday unless... But even then, you know how it is, whatever you get you want to hop it up.

I have seen used/older 175's for sale and now wonder which to get? I'm certain there are better years/brands than others to look for but I have no idea what to look for. So I joined this forum. If as you guys say, my 115 has peaked at birth, then I do need to get a V-6...but which? My only hope for the immediate future is a used one. That is a bit scary to me. I need to learn before I shop and buy at this point.

To me joining this forum is learning, thanx for the help and time to answer these questions. I'm not sure where else to go to start learning.

I would really like to have answers to the questions above anyway.

[j_martin]

I think you would spend less money and get much more gain by selling what you have, and looking for a good used v6 175 hp. A sleeper that might be pretty snappy in your setup would be an XR4 or XR6 mercury.

hope it helps
John

[fishlips]

I think you would spend less money and get much more gain by selling what you have, and looking for a good used v6 175 hp. A sleeper that might be pretty snappy in your setup would be an XR4 or XR6 mercury.

hope it helps
John


What year(s) would I look for this motor? Now, if 175 hp is the same with all motors are we then talking only weight differences...or durability too?