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ns70a2 no get up n go?

C

cjinkser

New member
Well I have the boat for quite some time now. And it just do sent get up and go anymore.
I have done the obvious to me and changed the plugs and cleaned and re tuned the carbs. But it just dosent have the out of the hole power anymore. If i have my self and girlfrend with gear the boat strugles to plane out. When it does i only get about 18mph out of it. When i bought the boat 15 years ago it would do 30+ mph. I just dont get it.
Is my motor shot??

Any help would be great
Thanks
Cj
 
[QUOIE=pI anv;480904]What is your compression? Have you checked for a spun prop hub? What is your WOT RPM?[/QUOTE]
Haven't done a compression check yet. I will do one this weekend and get back with that. What should my compression be with what kind of max variance between the 2 cylinders?
How can i tell if the bearing is bad?
And i have no tach on the boat. But when it won't get up n go it is laboring trying to get rpm but don't gain hardly any. When it is just me in the boat she gains rpm and goes pretty good.
 
No more than 10% variation between cylinders; better yet is under 5%. The precise compression number isn't critical, since gauges vary so widely.
If you make a pencil or marker, or scribe line across the hub and nut/washer, then go for a WOT run, the line should still be aligned after the run. If not, the rubber hub is slipping.
Get a shop tach on the motor to check WOT RPM.
What method did you use to clean and "tune" the carbs?
Are the carbs in sync with the ignition? Has the motor been de-carboned lately?
What fuel are you using, and how old is it?
Is there any visible damage to the prop, such as a bent or chipped blade?
What do the gas and oil filters look like? Any blockage or leaks?
Do you always run the carbs dry at the end of the day?
 
pvaI5newlase than 10% variation betI don't run the careen cylinders; better yet is under 5%. The precise compression number isn't critical said:
I pulled the carbs apart and used a cleaner solution bath and small burst of compressed air to clean them.
The carbs are balanced with each other. I used my balance gauge that I use on my motorcycle. It uses vacuum.
How would i sync them to the ignition?
How do you decarbon the engine? I am using 97octane mixed 50:1 with marine stabill in it.

The prop is new last year. And the pitch was the same as the one that came off.
The gas filter is good and no leaks. No i don't run the carbs dry. I use the boat every few days. It sits at the dock and we run it almost everyday to go fishing or a short cruise.
Click to expand...
 
Sounds like you got the carbs cleaned and balanced nicely.

The link-and-sync procedure (in the Factory service manual) basically allows you to get the timing advance correct both at idle and WOT, mechanically. If none of the stops or rod lengths were changed, you are likely OK, but it never hurts to chack, Also verify that the choke isn't sticking shut (but you would probably notice that due to smoking, etc).

Decarboning is done by running a special detergent through each carb throat while at high idle; then letting the motor sit for an hour (or overnight), and then running the loosened stuff out for at least 15 minutes. It blasts the carbon from the combustion chambers. Smokes like crazy!

As long as the carbs don't sit with fuel in them for over a week, you should be OK.

Are the oil recirculation tubes on (and the check valves in them)?

What do the plugs look like now?
 
Is that detergent like seafoam?
Also i cant findt a service manual. All i have is the parts book.
The plugs look great. Dark brown. And a little oily.
This is why i dont get why this engine isnt running like it should!
Everything is like it was when I bought the boat.
 
The best product currently available is OMC (Evinrude) Engine Tuner. Seafoam is pretty much just mineral spirits.
The motor is quite obsolete, and the original manuals were discontinued years ago. I do have a reprint available for $25 at the office.
 
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