91 johnson 225 vro running issues

[mickab]

i have a johnson 225 vro 91 model and i have a few issues, first at an idle i have a dead miss in the motor and it sometimes kills the engine. the second is when first started and taking off it runs just fine but around 4000rpms it starts to surge like it running out of fuel. but it will run good under 4000rpms about 45 mph. when i stop and fish awhile and go to take off again the motor starts just fine(with the miss still) but i can dig into the throttle cuse it seems to be starving for fuel but if i run it just above idle for 5 min or so it will finally take off and run great up to 4000rpms. so i figure it a fuel problem but not sure of what else it could be. the only thing i have done so far is replace the fuel line from the tank to the fuel pump. with no change. ive drained and cleaned the fuel tank and filled with fresh fuel. so now back to the drawing board. any help with this would be very welcomed.

 

[j_k_bisson]

Re: 91 johnson 225 vro running issues

Well this sound like a very common issue here on Iboats.

Unfortunately you are going to have to go thru all the test proceedures to figure out what is wrong with it.

They are;
Compression Test of each cylinder
Spark Gap test of each cylinder (7/16" gap)
Fuel flow/fuel air leak test.

The compression test is looking for the highest to lowest deviation number. No more than 10%
Spark gap check the strength of the ingnition system
Fuel is fuel, I would check and see if you can get the primer bulb tight. Then review the compression numbers to see what cylinder you need to look at for the fuel side.

Old school fuel spark, compression....

Post your results and let us know.....

 

[mickab]

Re: 91 johnson 225 vro running issues

ok will do, but i forgot to mention that when i first bought the boat two months ago i ran it and it performed flawlessly and ive fished it probably 20 times. just this past weekend is when the problem started. but will do all the checks and let you know.

 

[mickab]

Re: 91 johnson 225 vro running issues

ok went home last night and did the compression test on the engine. all cylinders were really close to each other but only about 80 psi. not sure if thats ok or if my gauge is off. but thats what i got. primed the ball and fired the engine up and man it hits on the first crank so pretty but still got the miss. i havent done a fuel pressure test due to the fact i dont have a gauge for that but im going to take it to the shop today to let them do the rest of the checks. but alittle more history about the boat. when i brought it home i cleaned it up and checked almost everything, i seen that the 37 gal tank had about 5 gals of water in the bottom so i drained and wiped out the tank so i know the engine is getting good clean fuel. it didnt have a fuel water separator so i added one but had to take it off beacuse it seemed to cause a fuel restriction when i installed it, would really like to put it back on cuse i know what could happen. i have two other boats but they have mercs on the back of them and are maintained very well and would like to get this one up to par. so hopefully ill get some good news in the next few days. ive heard everything from fuel problems to electrical. so if anybody that has ever had the same issue id like to know their fix. i trust the mechanic im taking it to he has done work on all my boats for years and never done me wrong but with anything several heads are better than one. thank you all for any and all advice.

 

[j_k_bisson]

Re: 91 johnson 225 vro running issues

80 is normal. Mine is around that number, actually 85 psi. Not to worry. That is your major issues you could of had. All others are minor in a sense. Untill the other checks are done it is very hard to tell what is wrong with it. Sorry. Let us know what your mechanic finds along with the reading form the fuel pressure check and the spark gap check. It will tell alot.

As to the water separator, it should have not effected anything. Was the filter used? They'll gum up if left to dry out with fuel in them. Also it could be an indication that your fuel pump is weak or your primer bulb is going. Might want to check both those out. Fuel pump can be rebuilt, but will need to be pre mix oil only afterwards. Might not me a bad idea seeing the age of the motor.

Just some thouhts. Hope it helps....

 

[mickab]

Re: 91 johnson 225 vro running issues

well it was a brand new fuel water separator, housing and all so thats what led me to think it is a fuel issue but it could be a number of things like you said. On another subject when the boat was running fine in the beginning i did notice that the rpms never really went above 5100 rpms at wot, about 56mph. im assuming that it should be turning every bit of 5500 or more right. ive read other post about this and heard that the lower unit could be to far in the water. not sure though. it is on a jack plate and it has an after market prop, dont know the size off the top of my head, so what do y'all think?

 

[j_k_bisson]

Re: 91 johnson 225 vro running issues

Motor height and prop selection is a funny thing. It is all dependent on a number of things. The main one is the boat.

Without getting into all the little details to give you a complete answer, it sounds right. You pitch your prop so that it does not exceed the max WOT RPM. Basically bog it so it will not turn faster than the WOT.

The height is set to where the bottom cavitation plat on the out drive/lower unti should be even with the water height at WOT speed. If it is below the water level then it is too low and causing undue drag.