What could this be?

[wnaplay]

I am leaning towards a tune-up or possibly a fuel issue, maybe water seperator needs changed.

Boat is an 89 maxum with the v-8 5.0lx with thunderbolt IV ignition system. I believe its a 305.

Go out today and the boat starts and revs fine in neutral. Put it in gear and it wont plane. I leave it in gear and after 5mins it finally builds up enough speed to go about 30mph however it doesnt sound right. This process repeats itself everytime I try to move. After around 5mins of plugging along it finally opens up a bit and builds up some speed. If something was bad due to needing a tune-up wouldnt the problem stay consistant and the boat never open up? I have good fuel in it and I know its probably long due for a tune up. I just cleaned the little inline fuel filter and it was dirty. Any suggestions are greatly appreciated.

 

[zbnutcase]

Re: What could this be?

Maybe a dead cylinder or 2? Time for compression and leakdown tests!

 

[EddiePetty]

Re: What could this be?

..... I know its probably long due for a tune up. I just cleaned the little inline fuel filter and it was dirty. Any suggestions are greatly appreciated.

Kinda answered your own question there wnaplay!!!!

Start with a complete tune-up and we'll help with any remaining problems.

 

[wnaplay]

Re: What could this be?

I will work on a tune-up this week. Since the problem happens in gear and at throttle, can I safely diagnose the issue at home with the earmuffs? I hate running 30mins to the lake everytime I try something and want to see if the problem is solved. I would need to run WOT with only the muffs to keep it cool. What exactly is included with a full tune-up? I heard I can get by without necessarily changing the wires?

 

[wire2]

Re: What could this be?

Muffs only is a no-load test. It will still rev to redline even if 4 sparkplugs are removed.
Have a look at all 8 plugs. You may see 1 or 2 cylinders not right. Or, as mentioned, a compression test will tell the tale.
If the plugs are all a clean, tan color, and compression is ok, then your distributer may be retarded, points burned, bad condenser, bad hi voltage wires crack in coil tower or dist cap ...
You can sometimes spot a hi voltage problem by running the motor at night, (no lights on) and look for arcing or a corona discharge.

 

[EddiePetty]

Re: What could this be?

........I am leaning towards a tune-up .......and I know its probably long due for a tune up. ...... Any suggestions are greatly appreciated.

With a big Thank You to Don S., I would suggest you start here.....

http://forums.iboats.com/showthread.php?t=192804