Hi Mike, the deck / speakers & amp were new last year. So I don't think it's that. At least I hope not $$$. Replacing the plug wires is a good idea. Anything else to consider replacing in the spring tune-up?

No family in Brantford, a cuz-in-law in Cambridge, but most are up on the Bruce Pennisula. Dad grew up south of Lions Head (Hope Ness - Greigs Caves & area) and myself in Wiarton. Nice area.

Hey Vern... now that I see you're using a separate amp (not the in-dash amp), I can almost assure you it's a grounding issue with the amp itself. Where do you have it grounded? If it's to the engine block, you could have a grounding loop as discussed earlier. Try using the negative terminal of the battery. Don't use a composite metal or alloy to ground - make sure it's highly conductive. I've also heard of using *SHIELDED* RCA cables to fix it. There's a chance it could still be the head unit ground, so check all of those connections as well. A marine environment is torture on low/standard grade wires, terminals, splices, etc.

Personally, I wouldn't mess with plugs or plug wires since they won't "fix" a bad ground. And a bad ground is probably the culprit. Good luck with it.

I second the grounding to the battery terminal. It really is starting to sound more like a grounding problem than anything else, but your amp could be an issue too. Is there adequate ventilation around the amp to reduce the chance of overheating? Amps usually have a thermal protection circuit, maybe it's kicking on prematurely?

One of our resident stereo people is Doug (moondance100), he's got probably the most impressive setup on here, if I remember correctly, it's somewhere between 2000 and 4000 watts. I'll bet you he could help you figure out the problem. Drop him a Private Message and see!

The only reason i suggested the plugs/wires is because Vern indicated the motor was due for a tune-up anyway. Check with the marine mechanic but i think the 8mm silicone resistor wires are marine approved as are the Champion resistor plugs. I've used them on a 115hp Evinrude outboard in the past & got good performance.

I agree with the rest of you though...it does sound very much like a grounding issue with the radio and / or antenna and getting a proper ground in a boat can take a little extra work. I would still check the power source connections also to ensure they are clean and once sure of that you could use a little of that liquid electrical connection protector to seal out any moisture.

Mike, Chris, Ryan ... thanks for all the input on how to fix the stereo.

The Jensen is driven by a 100 watt amp that is located on the outside of the protected walls beside the engine and is ground to the battery as suggested. FYI - I had a audio shop guy install all at their shop (unfortunate trailer mishap while I was there - clipped a car bumper - rookie mistake). Stereo sounded great, but not when I returned to the water and the engine was running. I will contact mondance 100 as suggested. Thanks.

We've had place in Lions Head for over 30 years. I know a bunch of the local folks, probably several that know your dad. The family cottage is at 26 William, just down from the Hospital. I've got a slip at the marina.