Squealing noise - 502 mag
 

Hi all. I recently bought a 93 baja 32 magnum with twin carb 502. It is a single owner and had been stored for several years in dry dock. After much work it is back running again. One issue I am struggling with now is a sequel/screech noise from the port motor when quick revved in nuetral in the water. It is fine if you accelerate normally and at steady rpm. I have had the engines to 5k and no off noises. With the hatch up it sounds like the noise comes from the rear of the port engine. Is it possible the coupler is slipping on a quick rev? The boat performs flawless with normal speeds and plenty of power. Any ideas? I had the drives serviced, gimbals replaced and alignment checked before launching last month. Thanks in advance

Sounds like maybe a loose sea pump or power steering belt.

I agree to what TXHawk said. Or maybe the belts need replacing?

Thanks guys. I also replaced the fuel pumps before launch since they were shot and changed the oil in the water/fuel pump combo unit. I verified belt tension is good. I think my next steps will be to try removing the water pump belt and then the alternator belt for a brief start (few seconds) to see if the noise goes away under quick throttle blip. I sure sounded like it was coming from the rear, but if the coupler was slipping it would certainly not run well on plane, right? There is zero noise when underway and boat pulls perfect right up to WOT. Strange that it only squeals in neutral on quick rev.

slipping coupler will not drive the boat well and will put rubber dust all over the transom. Use a mirror to verify that all cables and lines are clear of the drive shaft area. were the couplers removed during service? using the wrong size washer on the flywheel coupler bolts will cause the bolts to rub the inside of the housing. Otherwise it is likely at the front of the motor.

Check belt tensioner bearing or maybe old belts that are now squealing with more tension, that need replaced. Match them up at any good auto part store.

My carbed 454 MAG would squeal when revving when I swapped out the alternator. Once I checked the tension and got the belt tight enough, no more slipping/squealing.

Just my 0.02

Thanks everyone for the info, sounds like I need to re-focus on the front of the engine. That is good, much better than a possible failing coupler.

The couplers were not removed during service. The shop replaced the gimbal bearings and serviced the out-drives. They also checked alignment. It sounds like I need to look closer at the front of the engine

take your belts off - check all rotation of all pulleys - focus on the water circ pump and that rotation they bind over time for a jist of it. Also belt tension and belt(s) condition along with checking for spot on alignment is very important. Check all of that out 100 %. Check the impeller area and plus for any loose brackets that holds these system down tight. Make sure you have noting loose that the belt circulates around.

Also power steering pump as well and that rotation. Make sure your pwr sterring res is full and clean -- with no rust in it.

The easiest way to find these sort of [problems - when engine is running use a high quality doc stethoscope to pin point your noise area. Been doing that for over 20 years for pin pointing. By fair a great problem solver fast and easy. I would change the water circ pump if applicable especially if it is over 10 years old. Let me know I have them made here in the USA for all marine apps per spec and ratings.