Top Feed Carbs

[rangoon]

Hey guys, something I'd like to run by you.Well, when I was taking an interested party for a ride in my boat(for sale)the motor burned up. It ate #2&#4 piston,#4 being the worst.It's a 1996 johnson 115 90 deg cross flow. Anyway, the guy that did my machine work and sold me the needed parts told me to re-jet or drill the jets,the high speed orfices. The one on the left side.004 & on the right side .002.This guys been in business forever. He said its the new gasoline that makes it run to lean. Does this sound correct? It has the top feed carbs. Thanks for your help.

 

[Benny1963]

Re: Top Feed Carbs

go to the evinrude parts site and look up the carbs for your motor and year and see what it started out with
yes fuel restriction can cause failure .

 

[tashasdaddy]

Re: Top Feed Carbs

i haven't heard this,but it just makes a bigger hole to clog. which is probably what cause your motor to burn up. clogged carb jets.

 

[Faztbullet]

Re: Top Feed Carbs

After reading your post twice you stated" the one on the left side.004 & on the right side .002". 2 & 4 would have been on same side not left an right side. Exactly which cylinders are damaged?

 

[Reggie08]

Re: Top Feed Carbs

I was told something similar but it was more related to the slow speed/idle than anything. A local mechanic told me I would probably need to re-jet or drill out my current jets or as he put it, it was gonna idle "like a 3-legged dog". He said high rpms probably wouldn't make much difference but it would help with lubicration.

 

[rangoon]

Re: Top Feed Carbs

When I brought my block in for boring he said it is todays gas that is the problem. He said my carbs probally had two screws, one on each side and told me to rejet or drill out, left side.004 & the right .002. After looking at my manual, it doesn't make sense to do each side differently, they are both high speed jets.(two barrel carbs). The motor is 12 years old but only had about 100 hrs.use. The boat sat for a long time. Also carbs appeared to be very clean. I'll shoot some carb cleaner through them and use them as is. I've had the boat for 3 years and sorry to say Katrina put a damper on water sports so the boat was used very little.

 

[Dhadley]

Re: Top Feed Carbs

Something to keep in mind - he's talking side to side, even though the carbs feed across, because one side (bank) usually runs hotter. However, the starboard side is the hotter of the two banks so unless he's talking about left & right as you face the carbs - it's backwards.

And, drilling jets will change the in & exit ramp angles and mess up the rifeling. It's possible to drill a bigger hole and make the motor run leaner. You'd be better off to make sure the motor is capable of 5800, run fresh 87 octane and maybe run a slightly cooler plug like the (Q)L77JC4s.