Rpm Loss Help???

[Javelin 353]

I have a 1991 johnny 70 hp vro removed. Ran boat today first time in about 3 weeks, would only turn 5500 rpm (usually will turn 6000) Had an extra person today so I did not give it much thought. But while trying to out run a storm at the end of the day it dropped from 5500 to 4800 would not run over 4800 back to ramp. Any Ideas ??? as always thanks for the imput !!!!

 

[russeller]

Re: Rpm Loss Help???

when was the last time you did the carb ?

 

[Javelin 353]

Re: Rpm Loss Help???

They were professionally rebuilt in Februrary and I always run fuel stabelizer

 

[DJ]

Re: Rpm Loss Help???

Check compression on all three. <br /><br />Let us know.

 

[Javelin 353]

Re: Rpm Loss Help???

Do you think something major is wrong???

 

[rickdb1boat]

Re: Rpm Loss Help???

Won't know until you do the compression test. Could be you just dropped fire on one cylinder(Hopefully) or it could be worse. Let us know the results of the comp. test...<br /><br />BTW- I hate to hear these things, as I have the same year and HP motor as you...

 

[Javelin 353]

Re: Rpm Loss Help???

can anyone recommend a good compression tester, and is there a certain way to do it???

 

[Solittle]

Re: Rpm Loss Help???

Buy one that screws into the spark plug hole in the head rather than one with a rubber tip that you hold. They can be bought at any auto parts place or Sears, Etc. Directions come with it.

 

[Caddpro]

Re: Rpm Loss Help???

I am having about the same problem. I did a compression test with the following results top to bottom- 140-130-125. I hope you find the cause, if so please post back so I might be able to fix my problem. Good luck. I got my gauge from Sears for $25.

 

[Javelin 353]

Re: Rpm Loss Help???

took compression check was 120 on all 3 cylinders . Top plug was slightly dirtier than bottom 2 maybe time to de carb???? any other sugestions

 

[DHPMARINE]

Re: Rpm Loss Help???

Javelin and others.... This motor needs spark,7/16 inch with sparkplugs installed,compresion 100 psi and up,but no more than 15 psi difference.Fuel,clean and getting ino the carbs.Once you have this,we can further diagnose.<br />DHP

 

[Javelin 353]

Re: Rpm Loss Help???

How can I check the spark and do I need to do it on the muffs

 

[Javelin 353]

Re: Rpm Loss Help???

Bump

 

[stairliftoheaven]

Re: Rpm Loss Help???

yo dont need to start the engine to check the spark. remove all spark plugs and hold each lead in turn 7 1/6" from engine block to check spark while somebody else cranks the motor. some important health and safety matters to be taken into consideration tho: hold leads with well insulated pliers or grips, and test the spark well away from the spark plug hole as there will be inflammable gasses floating around the vicinity!

 

[Javelin 353]

Re: Rpm Loss Help???

thanks for the info

 

[Javelin 353]

Re: Rpm Loss Help???

very weak spark lower cylinder corrision on some of the leads off of coil and rectifier lots of spark now and battery charging better will run tommorrow to check for rpm loss