Rattle at idle

[walleye seeker]

I have an alpha 1 gen 1 coupled to a 350mag mpi. At idle not in gear i get a little rattle noise from the rear of the engine near the coupler. Is this normal i see a grease fitting on the coupler not sure if i greased this on install last year. I beleive the coupler is original 1989 came off 4 cylinder bolted right on 350 mag. Also made noise with 4 cylinder in place so it is not the engine

 

[Aviator5]

Re: Rattle at idle

Exhaust shutters

 

[Don S]

Re: Rattle at idle

So you changed from a 4 cyl. to the V8 and it makes the same exact noise? If that is correct, I would look at the gimbal bearing and see if it turns nice and smooth?
When you put the Y pipe on, did it have exhaust shutters in it? Were they the new style?

 

[walleye seeker]

Re: Rattle at idle

So you changed from a 4 cyl. to the V8 and it makes the same exact noise? If that is correct, I would look at the gimbal bearing and see if it turns nice and smooth?
When you put the Y pipe on, did it have exhaust shutters in it? Were they the new style?

It had the oval shaped ones that are up high near the top of the y pipe. the rattle is down closer to the gimbal bearing more like a shaft flopping but no rithum to it as soon as you put it under load it goes away i just greased the coupler and it didnt seem to make a difference. Not really a rattle more like a clunk its heavier than what exhaust shutters would sound like and much lower. The gimble was just changed by a mercury mechanic probably 50 hrs on it

 

[Don S]

Re: Rattle at idle

Have you listened outside the boat? Maybe a ujoint or even a chip out of an upper gear could make noise you could hear inside and just the extra noise at higher loads would make it hard to hear. But still be there.

 

[walleye seeker]

Re: Rattle at idle

Have you listened outside the boat? Maybe a ujoint or even a chip out of an upper gear could make noise you could hear inside and just the extra noise at higher loads would make it hard to hear. But still be there.

Put a brand new out drive on it when i put the new motor in genuine mercruiser drive. Different gear ratio 4cylinder to 8 cylinder. Now that i think about . If i changed the motor and a new outdrive the only thing left is the engine coupler which i reused and the gimbal bearing only parts left and yes it made the same noise with the old motor. I have to pull the entire setup back out. I had a crack in the alluminum hull right below the outdrive welded
when i put the new motor in and it has cracked right next to the weld. So i have to do it all over again this time i think i am going to put a 3/16 alluminum plate about 24x24 over the back and recut the drive hole through it to take the stress of the thin aluminum hull. This is why im trying to address this noise while i have it apart.

 

[walleye seeker]

Re: Rattle at idle

Exhaust shutters

You were spot on ex shutters rattling

 

[Don S]

Re: Rattle at idle

That means you had old worn out dead shutters in your 4 cyl. exhaust pipe, and used old worn out dead shutters in your Y pipe when you installed it.

 

[walleye seeker]

Re: Rattle at idle

That means you had old worn out dead shutters in your 4 cyl. exhaust pipe, and used old worn out dead shutters in your Y pipe when you installed it.

You would be correct how important are these. I dont race around the lake and then slow to nothing. Its my understanding that is how water makes it way up there. Strictly fishing boat

 

[walleye seeker]

Re: Rattle at idle

Ok i am going to replace the shutters to get rid of the annoying rattle. What do i need my y pipe is a{ pre alpha I think} and my drive is alpha 1 gen 1. The y pipe has the 3 bolts on each side down by the y connection and is round not oval.The flappers are the ones with the pin running through it off centered. If they only make one like that then my decision should be easy. When i switched from the 4 cylinder to the v8 my buddy worked for a marina who had a whole pile of parts and his boss let us scrounge through for my necessary ex parts. I dont think the regular alpha y pipe would work with my risers to short.

I think my combination is pre alpha gimble WHICH EXPLAINS WHY I HAD TO USE THE OLD STYLE PRE ALPHA Y PIPE , ALPHA 1 GEN 1 DRIVE, 2003 350 MAG MPI ENGINE BRAVO WHAT A CONGLOMERATION BUT RUNS LIKE A TOP