1974 115hp help

[joeyd50]

Need some help guys, just put a 1974 115HP Evenrude on my sons 1994 Nitro Bass Boat, its only a temporary motor till he gets his 150 rebuilt. The guy he got the motor from said he was just out on the river with it a month ago. The motor will rave up fine on muffs but in the water it just boggs down and won't go over 7mph, starts right up and sounds great on the muffs, where should I look first.
Thanks
Joe

 

[bktheking]

Re: 1974 115hp help

Check the standard stuff, start with spark on all 4. If spark check's out, start with re and re and cleaning of the carbs.

 

[Joe Reeves]

Re: 1974 115hp help

Check compression on all cyls. What are the readings?

With plugs out, spark should jump a 7/16" gap with a strong blue lightning like flame.... a real SNAP! Does it?

If the above are as they should be, remove, clean, rebuild the carburetors.

 

[bktheking]

Re: 1974 115hp help

Joe, just a question. I just got a comp guage 4 months ago cause I started to work on small engines, if an engine wouldn't run first I check spark then fuel issues and then compression. We all know that 2 stroke engines use fuel as oil as their only source of lubricant. Why do all the troubleshooting experts such as you and the other guys that have been on here forever suggest compression as a first step. No gas/oil and no lube mean you could do alot of damage cranking an engine over at speed to read 2 3 or 4 cylinders say 10 times. Doesn't that cause more harm than good?

Once against , just curious as I'm new to 2 stroke tech.
I guess fuel would be a starting point before spark in that case.

 

[Joe Reeves]

Re: 1974 115hp help

Your line of thought is understandable, however, a 2 stroke outboard engine could be sitting in a shed for 20 years, then put on a workbench and be torn down completely. What would be found is that the entire inner crankcase is coated with oil, bearings, cylinder walls, crankshaft, etc. It just stays lubricated.

Compression is always a first. If there's a compression problem, there's no need to waste your time or the customers money going further. The next step would be to remove the cylinder heads for a internal inspection of the pistons, cylinder walls, etc if the owner so desires.

Think about it..... if say a two cycle four cylinder engine has compression readings of 120, 120, 120, 80, there is no way that the fuel system could be trouble shot, adjusted, whatever. And checking the spark would require just as many cranking revolutions as a compression check. As the ole Carney Guy says..... "Trust Me" (grin), do the compression check first.

 

[joeyd50]

Re: 1974 115hp help

Thanks guys, I had almost the same thing happen to my motor, I rebuilt the carbs and it was fine after that, but it don't hurt to ask. This is the best boating site on the net.
Thanks Again
Joe

 

[bktheking]

Re: 1974 115hp help

Your line of thought is understandable, however, a 2 stroke outboard engine could be sitting in a shed for 20 years, then put on a workbench and be torn down completely. What would be found is that the entire inner crankcase is coated with oil, bearings, cylinder walls, crankshaft, etc. It just stays lubricated.

Compression is always a first. If there's a compression problem, there's no need to waste your time or the customers money going further. The next step would be to remove the cylinder heads for a internal inspection of the pistons, cylinder walls, etc if the owner so desires.

Think about it..... if say a two cycle four cylinder engine has compression readings of 120, 120, 120, 80, there is no way that the fuel system could be trouble shot, adjusted, whatever. And checking the spark would require just as many cranking revolutions as a compression check. As the ole Carney Guy says..... "Trust Me" (grin), do the compression check first.

Got it, thanks for taking the time to reply.

 

[joeyd50]

Re: 1974 115hp help

Pulled the carbs apart today, top carbs needle and seat dried up stuck, waiting for kits and we can get this thing back in the water.
Joe

 

[Joe Reeves]

Re: 1974 115hp help

Be sure to manually clean those four high speed jets that are in the bottom center of the float chambers.

 

[joeyd50]

Re: 1974 115hp help

Thanks guys for you help, the motor runs good except, maybe some can help me here http://forums.iboats.com/showthread.php?t=350523
Thanks Again
Joe