Help,1988 GT 150 running bad.

[mrtool2u]

My buddy has a 1988 GT 150 on a 17or 18 foot Glastron boat. This is really weird. The boat will not run good until the motor warms up,then you run it for 10 or 15 seconds and it falls on its face. We are pulling the carbs Saturday. The compression is 90 to 100 in each cyl,,we will be doing a decarb this weekend also. He has never run above 4900 rpms for about 10 years and approx 20 hrs per year. There is something hooked into the fuel line past the fuel filter,,just a small line,like a 1/8 line going to what looks to be a small pressure switch with a few wires hooked to it,,,what is this. Some one told him thatthis motor had something that limited the rpms until the motor was warmed up,,,I have never heard of this,,can someone shed some light on this. Also,sorry for all the questions,,,could the exhaust be plugged,,and if so,how can we tell,and how do we correct it. Thanks in advance.

 

[tashasdaddy]

Re: Help,1988 GT 150 running bad.

have you checked the spark when it falls on it's face. sounds like a coil or the powerpack is getting warm and failing.

 

[emdsapmgr]

Re: Help,1988 GT 150 running bad.

Possible that you are running out of fuel. Will run fine, til the bowls are sucked dry. Check your fuel pump and supply line, anti-siphon valve. The electric pressure device is likely the cold start fuel primer system. Injects fuel direct into the carbs when you push the key in. The motor should have a cold-start power pack. Will advance the idle ignition timing slightly till the pack senses the engine is up to normal operating temp, then return the advance to normal. You engine should have a 5800 rev limiter. You really need to prop the engine to run at least 5500 rpm. At 4900 it is lugging.

 

[mrtool2u]

Re: Help,1988 GT 150 running bad.

The device that I am referring to has only a line to it,,no other line to the carbs.Also,,where is the anti siphon valve,and what exactly does it do. It is really not acting like spark or a powerpak. We will also be checking the fuel pump,,what should we be looking for.