Upgrade 1988 115 to 140

[TOOSTROKIN]

I have been told that the 1988 1.6 liter 115 hp omc is the same motor as the 140. Is this true? They both have the same specs as far as bore and stroke. They both have the bubble back exhaust. Other than the carbs what is the difference and would it be worth it to upgrade my 115 to a 140?

 

[WillyBWright]

Re: Upgrade 1988 115 to 140

What is the maximum horsepower rating on your boat? This question is most frequently posed by people that want to overpower their boats and not get caught. I strongly advise against cheating due to endless legal, ethical, and practical considerations.

 

[TOOSTROKIN]

Re: Upgrade 1988 115 to 140

The hp rating is 175hp 6 persons. Its a 1988 18 ft center console deep v. Its a sea drive.

 

[WillyBWright]

Re: Upgrade 1988 115 to 140

Yeah, I can see why you'd want more horsepower. I really doubt you'd get much better performance without upgrading to a V-6. At best you might get 3mph, but I'm thinking more like 1 or 2. Holeshot probably wouldn't improve much at all.<br /><br />To answer your question, there are quite a few managable differences. But I believe the deal killer is porting of the block.

 

[TOOSTROKIN]

Re: Upgrade 1988 115 to 140

Thats what i was thinking also. I may just have to live with this for now. Boat does fine with 1-3 people but when im loaded with 4 or more and alot of gear its a dog on trying to plane especially on a rough day.

 

[WillyBWright]

Re: Upgrade 1988 115 to 140

What do you have for props? You might want to consider a lower pitch for heavier loads. Mercury High-Five props do rather well on underpowered boats and you can get a hub to make it fit your motor.

 

[TOOSTROKIN]

Re: Upgrade 1988 115 to 140

I use a 13-7/8 - 17 pitch for lighter running. works great. 43 mph at 5500 rpm. Good hole shot. I use a 15 pitch when im heavy but have to watch my throttle. will go up to over 6000 on the tach real quick. I have not tried a 4 blade yet.

 

[WillyBWright]

Re: Upgrade 1988 115 to 140

Four blades might be too much. Performance might decline. You're adding blade area and that's harder work for the motor. High Fives have little blades that allow them to pick-up RPMs quicker with a smaller diameter than the 4s or 3s. It has vents that you can customize for holeshot. Top-end performance is quite good. You get the best of both worlds. And you can run the motor high on the transom and not lose bite. They do rather well as surface piercing props for speed, but in rough seas they also do well firmly planted in the water. They're quite expensive and I think they're only made of the large diameter gearcases.

 

[TOOSTROKIN]

Re: Upgrade 1988 115 to 140

I have heard they are quite expensive. One more thing. I have noticed some oily residue around the stator plate on top of the motor. I believe the top seal is leaking. Is is necessary to split the block to replace this seal or just remove the top plate and replace the o rings and crank seal.

 

[WillyBWright]

Re: Upgrade 1988 115 to 140

There's a seal puller that is hollow to fit over the crankshaft and screw into the rubber of the seal. A puller screw presses against the crankshaft and yanks the seal straight out. Many older Johnnyrude dealers have them. Otherwise I've had luck putting 2 tiny screws into the metal shell of the seal 180 degrees apart and prying up both at the same time with wire cutters.

 

[TOOSTROKIN]

Re: Upgrade 1988 115 to 140

Thanks for the tip. I will try that when i replace the seal.

 

[DHPMARINE]

Re: Upgrade 1988 115 to 140

When you replace that seal,more fuel will reach the upper cylinders,and you should see a bit more power.Best bet before trying to increase power,get what you have in top shape.<br /><br />DHP

 

[jimmbo]

Re: Upgrade 1988 115 to 140

There is no difference between your 115 and the 99.6 cuin 140hp. the crossflow 140 was always crankshaft rated. After 1984 OMC rated their engine at the propshaft. What had been the 140 was now rated at 110hp or 115hp depending on the year.<br /><br />Now the 1988 140 is a totally different engine, loop-charged, more displacement, and different midsection. No interchangability of parts here.