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Discussion Starter #1
ok so i just bought a 1981 miller and the boat is beautiful, i took it out for the first time this weekend, it has a 512 bbf in it, i had to adjust the idle and the water intake and thats about it, except one thing when i come into the 5mph zone and start to idle there is a skreaching sound coming from the motor, i cant put my finger on it so lets hear some ideas, only at idle there is a skreaching noise.......
 

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If you are 100% sure it is coming from the motor, the last time I heard that, it was a spun main. I have soun rod bearings and didn't know it till it was torn down. But a main will tell you like right now.

Hate to say this, but there really isn't much in a motor that skreeches.
Maybe something in the flex plate. Starter that didn't disengage can make a pretty ugly sound. Does it restart OK.
A spun main is a bitch to crank over. Does it start right back up?



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I had a carb base gasket make a terrible whistle once when it was leaking (only at Idle) , ..... E:)hand
 

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Discussion Starter #5
starts up with no problem, were would I check the pump because when I put into reverse it will stop screaching its almost like when I put a load on it it stops, and yes I have only run it in the water, and it only happenes when im coming in if I put the boat in the water and idle out its ok but when I come back in it starts skreaching on and off. Hmmmmmm 714 781 9389
 

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Alternater belt loose?
 

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The OD of your impeller may be brushing against the ID of you bowl. Pull the bowl and look for signs of wear on the inside "shoulder" ( I don't know what else to call it ) of the bowl. If you have an aluminum impeller you may see signs of wear on the outside shoulder of the impeller.
I had a similar noise I swore was coming from the engine. It turned out to be what I described above. I ground a little off the ID of the bowl and the scraping noise went away.
 

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I took the.belt off and noise is still there
Disconnect the driveshaft, restart engine. Does it still screech? How is the oil pressure? Any main bearing bad enough to hear any sort of noise will lose oil pressure. IMO I think it is in the pump, a shaft bearing or as posed above the impeller rubbing the housing....but wtf do I know, I'm a prop guy.
 

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It said it in my first post, wats the give away, and motors are motors.
Just re-read, no mention of a jet. No matter.
you can pretty much assume its a jet due to the Ford because I can count all the Ford v-drives I have seen(that were build in the past 30 years) on one hand, and they all belong to 058:D
In the 60s, Ford v drives were all you saw:)devil

Disconnect the driveshaft, restart engine. Does it still screech? How is the oil pressure? Any main bearing bad enough to hear any sort of noise will lose oil pressure. IMO I think it is in the pump, a shaft bearing or as posed above the impeller rubbing the housing....but wtf do I know, I'm a prop guy.
Had a 352 crank in a 428 block the rotated at about 8500. Never lost oil pressure. Probaly due to the fact it simply shut the oil off to that main and two rods. Damn thing could have wakened the dead though. Thought it was a fan belt till I let off and the engine locked.

I agree. Remove the drive shaft and run it. Chances are its the pump. But then, I don't crap about jets. Never owned one, never even riden in one.:D



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I would also look into the carb, scoop, arrestors.... reason i say that is because if there is a minor air leak around one of those items the air being pulled in could be causing the sound you are hearing.

I know when i'm idling in my boat the air being pulled in thru my spark arrestor whistles a bit, when it first happend i had no clue what it was...

Just an idea.


OH yeah and weren't you the guy that posted up looking for "an 80 MPH jet boat"? What did you end up getting? Tell us more.
 

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Discussion Starter #15
I would also look into the carb, scoop, arrestors.... reason i say that is because if there is a minor air leak around one of those items the air being pulled in could be causing the sound you are hearing.

I know when i'm idling in my boat the air being pulled in thru my spark arrestor whistles a bit, when it first happend i had no clue what it was...

Just an idea.


OH yeah and weren't you the guy that posted up looking for "an 80 MPH jet boat"? What did you end up getting? Tell us more.
ya i am that guy i bought a 81 miller with a 512 bbf and dominator pump, the guy is in folsom ca i drove 900 miles total to get the boat, here are some pics
 

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Discussion Starter #17
The boat runs great I havent put it to the test yet cause im still learnimg how to drive, this is my first fast boat so I want to do it right.
And yes I cant wait to get her up on keel in the mid 80s, I was told I have a sickness its called good lookin fast boats
 

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90% chance it's the pump. When they come to an idle they lose bowl pressure and the impeller has no load against it. I hear it all the time when firing jets on the trailer. Usually more prevalent with a SS or mag bronze impeller, but have heard it with both. To be honest, I really don't know the exact mechanical reason some do and some don't. I believe it is harmonics and has to do with many things. Impeller balance, tail shaft to bowl bearing clearance, play in the splines, etc. If the noise goes away as soon as you raise the rpm's even a little (bowl pressure, impeller load) you are probably fine.

Disclaimer: assuming nothing is failing of course. :D

Edit: My second boat when I was young was a Miller Jet. Set it up as we would have a race boat. Turbo BBC. That boat hauled ass.
 

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i don't fire on the trailer. but at idle with an ss impeller, it's not uncommon to get a loud "rattle".
but i've never heard a loud screeching at idle. if i did, it would be shut off and disected until the problem was identified. there's a thrust bearing in there that is pressed on the shaft. part of it's function is to prevent the shaft from moving forward or backward. if it's starting to fail, bad stuff can happen as it will only get worse and take more parts with it.
 
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