Noise coming from front of engine

[Tman1971]

I’ve got a 1974 searay SRV 190. It has the 4 cylinder mercruiser 160hp. It runs great and idles really good. No problems running but at idle everything sounds good and there is no noise but when I give it just a little bit of gas I start hearing a sort of scraping like noise coming from the front of the engine. It sounds almost like a pulley rubbing but none seem to be rubbing. I wouldn’t really call it a pinging noise but some might. But it’s definitely coming from the from of the engine. I’ve heard an alternator bearing go out on a car before but this is a higher pitched sound that really sounds like scraping. Is there something on the front or inside the front of a boat motor like this one that any of you guys know would cause a scraping type noise? When I idle it up the noise just maintains and doesn’t get louder. It’s not absolutely constant either. I can hear quick short random breaks where to noise quickly comes and goes. Could be described as a rattling grinding sound I’d say. If you’ve ever heard a loose muffler shield under your car grinding or rattling from the vibrations of the motor, that’s what it sounds like to me coming from the front of the motor. Any ideas on what this could be? Thanks

 

[wellcraft-classic210]

Hard to say -- But hare a re a few guess's

The main water pump on the engine can do that -- usually if that's the case you can move the pulley up and down a little by hand as the baring will be worn significantly.

Loose bolts on pulleys is another possibility.

 

[Bt Doctur]

you have what is called the 470 motor, has no belts except a power steering belt.(maybe) No alt, it uses a stator charging system. magnets and coil . loose/damaged magnets will cause a racket .

 

[kenny nunez]

The noise could also be caused by a worm timing chain tensioner shoe letting the chain contact bare metal.

 

[nola mike]

you have what is called the 470 motor, .

1974?

 

[Bt Doctur]

It has the 4 cylinder mercruiser 160hp,
maybe somebody replaced the motor or its a in line 6 and he miscounted the cylinders
can only go by what the poster posts.inline 4`s are 140 max

 

[nola mike]

That would literally be the first conversion TO a 470 :-D

 

[Bt Doctur]

Well they are the only inline 4`s rated to 160-170 Hp. unless it had the inline 6 and they replaced it with the same HP inline 4 ?

WE NEED PICTURES

 

[Bt Doctur]

 

[Bt Doctur]

or this

 

[Maclin]

Tman1971 Is this the boat you just bought? If so, you had it described as 1974 Sea Ray SRV190 Stern Drive with the 6 cyl 160hp engine.

 

[Tman1971]

My bad guys, it is a 6cyl. All the comments give me some good ideas of things to check. Somebody did add an alternator at some point. Maybe they left something inside that’s come loose. But I’m definitely gonna check that water pump pulley and the timing chain too. Might be worth just going ahead and replacing all that to be safe if it doesn’t look to have been replaced in the last several years. I know almost everything else on the motor and outdrive has been replaced so hopefully the timing chain and water pump has too. I’ll let y’all know what I find. Thanks for the help. Wish you all could hear the noise somehow...

 

[Tman1971]

I’ll make a recording late tonight after work and post it on YouTube then I’ll share the link on here.

 

[kenny nunez]

Since there is no timing chain on your engine try removing the belt and start it for a few minutes. Your engine should have a fiber cam gear which is quiet. If the noise is the water pump be sure that the replacement has a cast iron, plastic or stainless impeller. Stamped plain steel will not last and will cause overheating.

 

[Tman1971]

Thank you Nunez. I didn’t know it doesn’t have a chain. And didn’t know that about the water pump impeller. I’ll be sure to get one that isn’t plain steel if I have to change it. But first I’ll try it without the belt if nothing else seems obvious like the water pump pulley moving or loose bolts or something. With the motor running so good I wouldn’t think this noise would be anything major but I know it can be a sign of something major about to happen. I really hope it’s what the other gentleman said about the magnets or something to do with the stator. Maybe when they put the alternator on it they left all that stuff in there and is just loose and making a racket and I can just go in and take it all out once I figure out where all that stuff is.

 

[Bt Doctur]

If you have the GM inline 6 cylinder ,you have a alt system, not a stator system

 

[achris]

Your cam gear is aluminium, not fiber. The original Chevy 6s had fiber to reduce noise, but it would rip teeth at about 80,000 miles, so Merc specced the gear to be aluminium for their application. . Your engine circ pump impeller should be cast brass, nothing else, no plastic or cast iron :facepalm:.. And the pump backing plate needs to be stainless steel.

Chris.........

 

[kenny nunez]

The GM inline engines only came with cast iron water pump impellers from the factory and none of them had a backing plate.
A brass impeller would have been excellent however.

 

[Tman1971]

Ok, Great. Thank you guys. I’m finally off for the weekend and plan to dig into it and see if I can figure out the noise.
By the way, can any of you tell me what weight gear lube I should use in the foot and how much it takes? I assume the engine oil and the gear lube in the foot is the only oil and lube that there is correct?

 

[achris]

The only oil to use in the drive is 'Quicksilver High Performance Gear Lube'. Available form any Mercury dealer and I believe a few hardware chains carry it (I'm not local , so I don't know your supply chain structures)...

It will take just under 1 litre.

Engine oil should be either straight weight 30, or 25W40 if that's not available. Those engines take about 4.7 litres (with a filter change).

Chris.......