vibration issue

[99seapro]

I have a 2000 Johnson Ocean Pro 175 and last season developed a BAD vibration at slow speeds such as going through no wake zone. Idles well with an occasional sneeze while cold, but smooths out when warm. It runs perfectly when on plane. Any ideas as to the problem? Where should I start? I have run it probably 25 hours since it started and it persists. Could I be damaging further by running?

 

[Black as]

Re: vibration issue

I have a 2000 Johnson Ocean Pro 175 and last season developed a BAD vibration at slow speeds such as going through no wake zone. Idles well with an occasional sneeze while cold, but smooths out when warm. It runs perfectly when on plane. Any ideas as to the problem? Where should I start? I have run it probably 25 hours since it started and it persists. Could I be damaging further by running?

Spin the prop by hand and see if your drive shaft is bent also check the prop for any damge

 

[CharlieB]

Re: vibration issue

How long since the carbs were cleaned?

Dirty idle jet or idle AIR jet can cause an occasional lean cough/misfire yet run perfectly fine at all speeds above an idle.

 

[kenmyfam]

Re: vibration issue

Is the prop in good shape and the shaft running true ???

 

[99seapro]

Re: vibration issue

I have only had this boat and motor for a year and have no clue when the carbs were cleaned last. The prop has a few minor dings in it but they were there before this vibration started. I know I didn't hit anything. I remember the day it started I put in some gas made a 15 mile run on plane and when I got to a no wake zone it started and hasn't gone away since then at low speeds such as 5-10 mph.

 

[tashasdaddy]

Re: vibration issue

i would start with spark and compression check, then prop shaft.

 

[99seapro]

Re: vibration issue

i would start with spark and compression check, then prop shaft.

I will start there. whats the best way to check spark and intensity of spark?

 

[tashasdaddy]

Re: vibration issue

with a $12 adjustable spark tester. i remove all my plugs, secure wires so the do not ground to block, and do my compression and spark test at the same time. open tester to 1/2 inch,

http://forums.iboats.com/showthread.php?t=313963&highlight=compression

 

[izoomie]

Re: vibration issue

This may be a dumb question but have you run all the gas out that you bought when the problem started. I'm thinking bad gas.

 

[robert graham]

Re: vibration issue

The first thing to do is remove and inspect all spark plugs for an indication of problems, like carbon fouling, water leakage into cylinders, rich mixture, etc.
Good Luck!

 

[tashasdaddy]

Re: vibration issue

would you not do that, doing a compression and spark test????

 

[robert graham]

Re: vibration issue

Hopefully!

 

[99seapro]

Re: vibration issue

tested the spark today and set the tester to the 20 mark which looked to be at least 1/2" and the spark jumped the gap consistantly on all wires. Didn't do compression check due to no gauge yet. All the plugs have a thin coating of dark brown residue that easily wipes away. Right now they're also very wet due to fogging oil. Also I looked in the plug holes and the top of the pistons are black should I decarb too.