1988 Starcraft Islander 5.0 driveability problems

My engine is a 5.0 mercrusier I/B, starts hard and is very sluggish. I have replaced cap,rotor, plugs, wires, fuel pump and filters, rebuilt carburator, and ignition coil. Ran 100 gallon fuel tank empty and refueled with fresh gasoline. Don't know much about the ignition amplifier, could this be my problem? I use this boat strickly for fishing, trolling speeds of 2-3 MPH, top cruising speed used to be around 33-35 MPH, now will only reach 15 - 17 MPH. I need this boat to perform better to get back out of the lake at a resonable hour! Looking for suggestions

Re: 1988 Starcraft Islander 5.0 driveability problems

I would start with a compression test. Here is how to do it so it means something.<br /><br /> http://www.boatfix.com/merc/Bullet/97/97_25.pdf <br /><br />Since it seems sluggish (I assume it means it turns over slowly) also get the batteries load tested, check the cables (positive and negative) to be sure they are not corroded away. Be sure they are tight, wingnuts are not a good thing. Use a regular nut and a wrench and tighten them down after cleaning. You could also have a sarter problem, may want to have it tested. Bad bushings will make them slow turning.<br />When you changed the plugs, did you see any rust or indication of water on the old plugs? Any of them look clean as new?<br />How old are the exhaust manifolds and risers?

Re: 1988 Starcraft Islander 5.0 driveability problems

Driveability problems, not having starting problems associated with cranking the engine, that is fine. A compression test is my next option, this will tell me a lot about the condition of my engine, I will be doing that soon as time permits, and as the weather warms a little bit in good ol' New York! I am in the process of getting a manual so i can get some wiring diagrams and test the "Ignition amplifier". Sometimes plugs are sooty and sometimes plugs are clean? This is why I am leaning towards the electrical system for proper spark for each cylinder because of that. I have not located any vacuum leaks and timing chain appears to be fairly tight, don't know if the characteristic of the cam wearing out would apply to the mercruiser as it did with 1980's small block Chevy car engines, maybe. I am frustrated because this is cutting into my fishing time!

Re: 1988 Starcraft Islander 5.0 driveability problems

My engine is a 5.0 mercrusier I/B, starts hard and is very sluggish.

Click to expand...

Not sure how I came up with the hard starting problem. did I misread what you said in your first sentence? <br /><br />Look at the connections to the Ign. Amp. many times I have found them corroded and the pins breaking off. If they are corroded, replace the amp and the small harness that attaches to it.