Out board will not get over 2500 rpms

[84skeeter]

Hello, I have a 1988 Johnson 150 GT. I have had this problem since I bought the boat ( 84 Skeeter Starfire 150).<br /> I can get up to 2500 rpms an that is it will not climb any higher. I put it in the shop,an had it checked out ,The compression was at 110 on all cylinder or within 2%. ignition checked out ok, they rebuilt the carbs, an set timing, and installed new plugs. It ran good for a couple of trips out( 2 tanks of gas), but then the problem reapeared. I have already paid over $600.00 dollars to fix the problem , just looking for a few ideas,before this problem takes me to the cleaners.<br /> Thanks for any help you can give.

 

[ob]

Re: Out board will not get over 2500 rpms

When this problem re-arose ,did you push in intermittedly on the key primer to see if engine would pick up?This could have helped narrow down a possible restriction in one or more of the carburetors.<br />Also,did you try pumping the fuel primer bulb and see if the engine would pick up?This could have helped narrow down a fuel delivery issue(ie failing fuel pump etc.<br /><br />Seems the major item you listed that was done at the shop was the carburetor rebuilds.Did they verify whether you're fuel tank was contaminated or not?<br /><br />The next item in line would be an intermittent ignition issue.Will all plug leads jump a 7/16" gap to ground with a crisp blue snap at cranking speed with the engine cold? How about when the engine and ignition components are warm?<br /><br />Also need to eliminate any possibilty of air or fuel leaks on fuel hoses from tank to carburetors,to include the fuel primer solenoid valve.

 

[84skeeter]

Re: Out board will not get over 2500 rpms

Hello,<br /> I did try the key primer,It drop from 2500 rpms to 2200rpms.<br /> Tried the primer bulb no help.When the shop rebuilt the carbs ,He said he didn't see anything in the carbs or bowls.He ran the motor on the gas that was in the tank when he hooked it back up to the dyno.He said he checked an was getting the right amount of fire, I will get a spark tester tomorrow an check it myself.<br /> I did start to drain the tank where I can clean it.I saw some redish blochs in the bottom of the jar. I am going to take the tank out an clean it and replace the fuel lines an bulb.<br /> I will let you how it does,<br /> Thank you for your help.

 

[ob]

Re: Out board will not get over 2500 rpms

Sounds like a good plan 84 skeeter.Is that a metal tank by any chance? If so,once they get any water intrusion and begin internal corrosion,its a good idea to consider replacing with new or even going to plastic or fiberglass.be sure and post back on your results and myself or someone else can stick with you until you get this thing ironed out.Good luck.

 

[84skeeter]

Re: Out board will not get over 2500 rpms

Thank you ob for the help, I have cleaned the tank and replaced fuel lines and bulb. The boat will now get up over 2500 rpms now, but i still notice it is sluggish on the climb from 2500 to 3000. I have changed from a 4 blade 23 pitch prop to a 24 3 blade prop it planes a little faster but still not like it should.<br /> The fuel pump was at a little over specs for min. pressure would that cause the problem? I am going to take it out again in the morning to see how it does.<br /> Thanks again for your time an info.

 

[emdsapmgr]

Re: Out board will not get over 2500 rpms

Any chance that you are overpropped? a 24 is a pretty tall prop for a 150.

 

[seahorse5]

Re: Out board will not get over 2500 rpms

Give us the complete model number on the motor.<br /><br />It may be equipped with the SLOW system that keeps the rpm about 2500 if the temp switches sense an overheat, or have a short to ground somewhere. A knowledgeable mech can check that out very quickly.