messed-up midrange

[fishinlooney]

I'm stumped! I have a 1987 50hp Evinrude with a less than 1 year old vro pump. It idles great and runs good up to planing speed (about 12 mph) and runs at 3/4 to full throttle really well also (tops out about 26mph on my 16 ft Mirrocraft.) My problem appears when I'm pulling my 8 year old daughter on a kneeboard and trying to maintain about 13-18 mph. It surges and slows down and I can't hold a steady speed. I fish most of the time so the motor performs BEAUTIFULLY for me 95%of the time, but on those hot summer afternoons I want to give my young fishing partner a little fun. I've taken off the backfire arrestor to access the carbs while running but can't see anything obviously wrong (fuel leaks, shorting out, etc.) If it were an air leak would it show up only in the midrange? Sorry for the long post. Jeff

 

[Dhadley]

Re: messed-up midrange

Well, thats always been a problem with carbs that have only a low and hi speed jet. Youre right in that transition range. There are a couple of things you can do to help. <br /><br />First make sure the set up is correct overall. The rpms should be at 5800 with a normal load, you should have Champion plugs, fresh 87 octane and good TCWIII oil.<br /><br />Lots of folks will use their spare prop for skiing/tubing thats a couple of inches less in pitch. <br /><br />Now, if your overall set up isnt maxed out it will help to do so. Tell us more about your set up and where you boat. At altitude it may be benificial to do some jetting.

 

[fishinlooney]

Re: messed-up midrange

Dhadley,<br /> Sorry I forgot to mention that last summer I was able to tow with no problem. This is a new situation that has only shown itself in the last couple of weeks since the weather finally got nice. The boat has spent it's entire time up here at altitude so I'm pretty sure the set-up is O.K. I run fresh gas often because I boat on a small lake and only carry a 3 gallon tank which usually lasts all day, usually 91 octane. Is 87 better for this motor? A friend mentioned that he thought it may be a messed up float in one of the carbs. Possible? Thanks for the quick reply.

 

[Dhadley]

Re: messed-up midrange

Ah! If it was OK last year, went into hibernation and now its not -- that is indeed most likely a carb issue. We call it "Spring fever" and is usually some gummed up passages. I'd just clean both carbs and put in new kits. Very simple. Not a big deal at all. <br /><br />Yes, 87 is all thats required.

 

[fishinlooney]

Re: messed-up midrange

I'll give it a shot and let you know how things turn out. Thanks so much for your help. Jeff.