Evinrude 88hp Carb upgrade?

[Starr MUrray]

I have a 1991 Evinrude 88hp. If I change the carbs to a set of 115hp carbs will it bump up the hp? Will it mess anything up on the engine? Thanks.

 

[Dhadley]

Re: Evinrude 88hp Carb upgrade?

Welcome!<br /><br />You can use the carbs, the 115 flatback crossflow and the 88 were real close to, if not exactly, the same porting. I doubt you'll see much difference. <br /><br />Youll probably gain more by maxing out your set up now. Tell us more about what you have and how it runs.<br /><br />Top rpm, top speed, what prop, jackplate or not, have you tried raising the motor, what boat ....things like that. And what youre looking for specifically.

 

[Starr MUrray]

Re: Evinrude 88hp Carb upgrade?

I have A Glastron 1971 GT-160. It's turning 5200rpms at a speed around 47mph right now with a worn out old 19 pitch prop. No jack plate. It runs good but I really want to get 55mph out of her. What can I do to the motor to get her to that speed? The cavitation plate is about an inch and a half above the bottom of the hull.

 

[LubeDude]

Re: Evinrude 88hp Carb upgrade?

For what its worth, Ill chime in. <br /><br />Let be get this straight, you want "8" more MPH.<br /><br />Let me be blunt, (Im good at that), IT ANINT GONNA HAPPEN! <br /><br />I would be surprised if you went out and bought a new 115 you would get "8" more MPH. Speed is difficult to get on the water.<br /><br />You are over propped right now, Id drop to a 17, three blade stainless. <br /> Welcome to I boats, we will do what we can to get you there.

 

[phatmanmike]

Re: Evinrude 88hp Carb upgrade?

ajackplate, trim tabs and a clean hull bottom will get you more speed, easier, and cheaper, than if you raised your HP

 

[Dhadley]

Re: Evinrude 88hp Carb upgrade?

Great boat! It has a bit more hook than the GT 150 but still a cool boat. Youre in the right ballpark with a 19. Whats missing is the jackplate. We might have to do some tweaking on the hull right at the back but I wouldnt rule out 55 just yet.<br /><br />Youll get more rpms with height. I take it that the motor is mounted all the way down now?

 

[walleyehed]

Re: Evinrude 88hp Carb upgrade?

LD, just for the sake of the poster here....with the help of Dhadley, I gained not only 8, but 11 with the same engine. The GT series Glastrons are runnin' mothers.....we sold a bunch back when....very popular, and I don't doubt he'll find 8...this boat responds quite well to changes in set-ups.<br />DH is the boss on this one, but one thing I did that is very simple and allowed more heigth, is tapping the top 2 water pick-up holes and plugging, then drill out the bottom weep hole (using it as a pilot hole) and fairing in the hole just like the ones above...allows almost 1-1/2" higher mounting (Of course this is Doctor Hadley's trick-not mine) and allowed the use of higher pitch with much more aggresive cup, creating a LARGE speed gain but still keeping the high RPM.<br />The man is a Legend, he just doesn't know it yet....

 

[Dhadley]

Re: Evinrude 88hp Carb upgrade?

I dont know about that -- its just that I've fell out of....er...I mean rigged a few Glastron GT's back in the day. I had a GT 150 once. Got it to just about 65. With a 1972 125. What a club for a gearcase! And the prop selection -- man if we just would have had todays choices...

 

[LubeDude]

Re: Evinrude 88hp Carb upgrade?

Well, Ive had egg on my face before, Its not going to easy though, but just maybe it can be done, Dhadley and walleyehed are the ones to walk you through it, if it can be. But with an 88, we will see.

 

[walleyehed]

Re: Evinrude 88hp Carb upgrade?

DH, I detect a challenge here....Hummmm... <br />I'm playin' with ya, LD, but the gain of 11 is true....it all depends on how good the set-up is to begin with..

 

[Dhadley]

Re: Evinrude 88hp Carb upgrade?

LD, I figure his 88 has to have more spunk than that ol 125 I had. Just the gearcase shape alone should count for something -- actually a lot!<br /><br />You ought to have seen the contraption we had for a jackplate. Remember on those motors you bolted two pieces to the tramsom and then slid the motor in them? Well this 2-piece plate thing bolted to the transom, then those 2 pieces bolted to it and ....never mind. Its too scary to think about now. And there was no such thing as a low water pick up.

 

[LubeDude]

Re: Evinrude 88hp Carb upgrade?

I certanly dont have the experience as you two do, so I have be sucking on the hind T** here as to if it can be done ot not. If you guys say it can be, then I have to agree.<br /><br /> Thats a neet trick with the water pick up. Can you do anything like that with a merc, or do you have you go with the low water pick-ups Ive seen which seems like a lot of trouble.

 

[Dhadley]

Re: Evinrude 88hp Carb upgrade?

Dont know about the Merc. Next time you have the lower unit off, or if you have one off already, look below the water pump where the water comes in. If the holes go all the way to the floor of that cavity, then no. If they dont, then yes you can extend the holes to the bottom. I have a feeling the Merc pick up holes go all the way to the floor. <br /><br />For some reason on the OMC's the bottom inlet hole isnt on the floor. Theres room for another one on each side. So, like Kenny said we add one to the bottom and close off the top 2 on each side. That allows the motor to be raised more and the inlet holes "stay" down.

 

[Starr MUrray]

Re: Evinrude 88hp Carb upgrade?

OK guys, First of all thanks for the info. What size jack plate should I go with? I can get my hands on a Panther Jackplate with a 10inch set back for fairly cheap. Is that set back too much? Some say 6inches is perfect for my set up. If I go with a jackplate could someone email me a diagram of how to modify the lower unit water pickup to raise it up higher. Thanks. 72sail

 

[Dhadley]

Re: Evinrude 88hp Carb upgrade?

10" on a GT 160....Thats a lot. Well, heres the deal. If it is too much, you can always sell it. As a matter of fact I may be interested. <br /><br />As long as you have enough steering cable (or hose) length, and its cheap -- lets try it. Thats really going to change the CG or balance point so be careful and go slow.<br /><br />My first thought is that it will create a lot of bow rise on holeshot. There are cures for that but dont be suprised.

 

[Starr MUrray]

Re: Evinrude 88hp Carb upgrade?

DH, If I can get my hands on it and if you have what you know would work for my application do you want to make a deal? I was kind of thinking that 10inches would be alittle over the top. I don't think I'll go with the 10incher but I will try to get my hands on it. If for no other reason than to Ebay it to pay for what I really need.

 

[Dhadley]

Re: Evinrude 88hp Carb upgrade?

I dont have a jackplate other than the hydraulic one on the Dusky. If I had a 6" manual I'd be glad to trade. There are many folks looking though for plates. It shouldnt be to hard to move.

 

[Starr MUrray]

Re: Evinrude 88hp Carb upgrade?

How hard is it to modify the lower unit for a jackplate set up? Thanks.

 

[Dhadley]

Re: Evinrude 88hp Carb upgrade?

I wouldnt modify it right now. i'd put the plate on and run the motor as is to establish a baseline.<br /><br />Can you raise the motor any now (without the jackplate)?