Screeching Noise from Frankenstein 383

[Kola16]

I apologize for the long story, but I will try to keep it short yet detailed. Ask questions if I need to elaborate.

I assembled a custom 383 stroker engine to replace my 350 block. More details in my signature, but it has a Holley Sniper EFI and Pertronix electronic ignition set to 12* at idle. The drive is an old Mercruiser 228. I don't have the money to upgrade to a Bravo drive, but I do have a drive shower and a raw water pickup that keeps the engine running at 170*F. I drive it nicely, not like a wild child due to the drive.

I put the engine in originally with a used OEM Bravo coupler and got this same screeching noise. I put alignment lines with a sharpie on this used coupler and sure enough, the lines were off. The coupler was spinning. When I pulled the engine out, I decided to replace the transom and stringers since there were some bad spots and I figured that was the problem. I rebuilt the transom to 2-1/4" and measured all the parallelism, thickness, flatness, and so on. The stringers were rebuilt solid too. Both engine mount stringers and stringers to the transom. All fiberglassing was rebuilt much better than what was done at the factory. Picture just for your curiosity after fiberglassing and reinstalling transom plate.


So with the new transom and stringers I put everything back in which includes the newer power steering ram, new OEM front engine mounts, new OEM Bravo engine coupler this time, OEM Bravo flywheel housing assembly, and OEM Bravo inner transom plate. The U-joints and gimbal bearing are also new and move smoothly.

To get the alignment correct, it took the stainless steel washers, spring washers, and fiber washers under the rubber rear engine mount bushings to get the alignment bar to slide in and out and spin easily with two fingers. That doesn't seem normal does it? I thought you use either the spring washers, or the stainless washers, but not both? But for me, that was the only way to get it aligned correctly. Anyway, took the boat to the lake joyously thinking I was done, only to get this noise again with the video linked above. My heart sank. It makes the noise when accelerating, but the noise stops when I pull back on the throttle a little bit. I can't really get it to make the noise on the hose, or in neutral on the water even when throttling up. I know it is not a belt or pulley because I took the circulating engine coolant water pump belt that also goes to the alternator, and power steering pump belt off for a second and still got this noise. There is still the crank mounted raw water pump that I suppose could make this noise, but the noise sounds like it was coming from the back of the engine. I did have alignment marks on the new engine coupler and looked at them, but to my surprise, they appear to be on. No spun coupler? I guess it could have done full revolution(s) and landed right back on the mark, but that isn't super likely. See the green mark below. It is hard to get a picture of so I apologize for the quality. The grease seemed to wash off all the other marks except 1 maybe which appeared to be on too.



So I am at a loss and I would greatly appreciate some help. I have spent all spring and summer working on this boat, and I am at a loss. My plan is to take the outdrive off to see if the alignment is still on, but would like some insight before I put more work into this since I am pretty burnt out at this point. Is my rear mounting setup wrong? Did I just somehow get a bad new coupler and it is the inner part that is spinning (between splines and rubber? I was told by one mechanic that it could be timing related!? Your guys' knowledge would be greatly appreciated. Thank you for your time.

 

[badrano]

To me it kind of sounds like something is being squeezed through a small opening under high pressure.
The sounds makes me think of operating a hydraulic piston like on a backhoe...the high pressure hydraulic fluid flowing into the cylinder through the control lever can sometimes make a squealing/squeeking noise.
The only thing that's really hydraulic on a boat is the power steering....could something be going on with the steering mechanism/piston??
Not sure how/why the power steering system would make such a squeal only under acceleration though.
What ever it is, it's happening when the engine is under more load during acceleration and that can't really be replicated if you're out of the water running on muffs.
The only other thing I can think of is maybe vacuum related where there is a pin hole leak somewhere and all that air is getting sucked through a tiny hole making that squeal/squeaking noise.

This is my apprentice level thought

 

[Kola16]

Hey badrano, you may be onto something. Before you replied I may have found a lead similar to what you are saying, but am not sure. I hear what sounds like the same noise mine is making in this video at the 11:25 mark:

In this guy's situation, the noise came from the Holley Sniper TBI itself (air leak?), and he fixed it with a different gasket and a spacer between the TBI and air intake. Thoughts? I have the same gasket and a similar air intake manifold that he has so it makes sense that mine would make the same noise. I'm going to try it.

 

[Kola16]

This! This is the same noise mine is making. It was fixed with a 4 hole spacer and 4 hole gasket. I'm going to give it a shot for sure.

 

[badrano]

I think I would agree....very similar sounds in thise videos.

 

[kd4pbs]

If the coupler were spinning, engine speed would increase and boat speed would decrease until shortly later you would go nowhere and smell the burning rubber.
Sounds like you are on the right track.

 

[Kola16]

Put a 1" 4 hole aluminum spacer on it with a 4 hole gasket above and below the spacer. Put it in the water today and the screeching is gone! Thank you all for the help!

 

[Scott06]

Put a 1" 4 hole aluminum spacer on it with a 4 hole gasket above and below the spacer. Put it in the water today and the screeching is gone! Thank you all for the help!

was it leaking vacuum or just noise from the airflow through mismatched bore sizes

 

[Kola16]

was it leaking vacuum or just noise from the airflow through mismatched bore sizes

I am not really sure. I read that the square bore gasket acts like a blade of grass between your thumbs when you blow on the blade of grass. It is kind of what it sounded like, but not really sure. All I know is that I'm boating again!

 

[Scott06]

I am not really sure. I read that the square bore gasket acts like a blade of grass between your thumbs when you blow on the blade of grass. It is kind of what it sounded like, but not really sure. All I know is that I'm boating again!

yeah good for a relatively easy solution. will be interested to see how the sniper works for you

 

[kd4pbs]

Glad that sussed it out!
A word of interest; usually when converting from a carb to EFI, it's best to either go with a manifold which has no exhaust crossover port or effectively plug the one that is in the carbureted manifold. The heat is helpful with the carb's air-fuel charge, but a detriment to the EFI charge.

 

[Kola16]

yeah good for a relatively easy solution. will be interested to see how the sniper works for you

I have had the Sniper for about 4 years. I had it on the last engine in this boat. I like it much more than the carb, but I wouldn't go recommending it to anyone that wants to ditch their carb. ESPECIALLY in a boat since the biggest downside of it seems to be that the display unit it comes with is not waterproof.

 

[Kola16]

Glad that sussed it out!
A word of interest; usually when converting from a carb to EFI, it's best to either go with a manifold which has no exhaust crossover port or effectively plug the one that is in the carbureted manifold. The heat is helpful with the carb's air-fuel charge, but a detriment to the EFI charge.

The exhaust crossover ports are covered in mine. I have an AFR Eliminator Dual Plane 4150 intake on it which does not have crossover ports.

​

 

[Scott06]

I have had the Sniper for about 4 years. I had it on the last engine in this boat. I like it much more than the carb, but I wouldn't go recommending it to anyone that wants to ditch their carb. ESPECIALLY in a boat since the biggest downside of it seems to be that the display unit it comes with is not waterproof.

I'm the opposite I prefer the carb on my boat as it can be fixed with simple hand tools.

So in your experience it holds up ok? My other hobby is muscle cars and you seem to hear mixed reviews for folks, mostly that some of the systems are not OEM quality systems like on modern cars

 

[Kola16]

I'm the opposite I prefer the carb on my boat as it can be fixed with simple hand tools.

So in your experience it holds up ok? My other hobby is muscle cars and you seem to hear mixed reviews for folks, mostly that some of the systems are not OEM quality systems like on modern cars

Mine has held up okay, but it is far from perfect. Like I said, I would not recommend it to just anyone. If the carb is working for someone, I would say stick with their carb. The Sniper is Coast Guard rated, but with that said, they didn't take the necessary steps for making it boat ready. The fuel pump relay was not waterproof so after that corroded twice relatively quickly, I switched it out for a waterproof relay and holder and now that is doing well.
The little display unit cannot get wet, so if there is potential for it to get wet, I have to put the canvas on my boat up, or do without it. Putting the canvas up isn't a problem for me since I do that anyway if it will be wet, but for an open boat without canvas, that would take some special doing or care for where you mount it if you want to display it.
The throttle body itself needs to be drained of fuel for winterization even if using non-ethanol or else it will be gummed up the next season. The throttle body/multiport injector thingy seems to be made out of cheap aluminum to me, but can't say for sure. I would say it is definitely NOT OEM quality haha.

I went through 2 rebuilt carbs before I switched to the Sniper. The problems I was having with the carbs were:
They were hard to start before warmed up.
The steel linkages for the butterflys would corrode.
On take-off, if I had a lot of weight in the back of the boat, the bowls would spill fuel into the engine, flooding it.

There are solutions to fix those carb problems, but I was fed up. I am happier with my Sniper, but it isn't without its set backs too so that is why I wouldn't recommend it to everyone. There is a Sniper "2" now that supposedly fixes some problems the original Sniper has for the car guys, but mine is doing well for me.

 

[Scott06]

Mine has held up okay, but it is far from perfect. Like I said, I would not recommend it to just anyone. If the carb is working for someone, I would say stick with their carb. The Sniper is Coast Guard rated, but with that said, they didn't take the necessary steps for making it boat ready. The fuel pump relay was not waterproof so after that corroded twice relatively quickly, I switched it out for a waterproof relay and holder and now that is doing well.
The little display unit cannot get wet, so if there is potential for it to get wet, I have to put the canvas on my boat up, or do without it. Putting the canvas up isn't a problem for me since I do that anyway if it will be wet, but for an open boat without canvas, that would take some special doing or care for where you mount it if you want to display it.
The throttle body itself needs to be drained of fuel for winterization even if using non-ethanol or else it will be gummed up the next season. The throttle body/multiport injector thingy seems to be made out of cheap aluminum to me, but can't say for sure. I would say it is definitely NOT OEM quality haha.

I went through 2 rebuilt carbs before I switched to the Sniper. The problems I was having with the carbs were:
They were hard to start before warmed up.
The steel linkages for the butterflys would corrode.
On take-off, if I had a lot of weight in the back of the boat, the bowls would spill fuel into the engine, flooding it.

There are solutions to fix those carb problems, but I was fed up. I am happier with my Sniper, but it isn't without its set backs too so that is why I wouldn't recommend it to everyone. There is a Sniper "2" now that supposedly fixes some problems the original Sniper has for the car guys, but mine is doing well for me.

what you outline is the same as others post on the car sites. While this provides many benefits, the guys who think it will be plug and play vs a carb are disappointed.

I know running a carb I will have to rebuild it 1-2 times during the lifespan of owning the boat, but I also like I can do this with simple tools and keep a carb kit on hand.

What carb was over flowing the fuel bowls ? I run the edlebrock 1409 have never seen this, only some dribbling after shut off (flooded on hot restart sometimes), and fuel bowls drying out if not used for a week

 

[Kola16]

what you outline is the same as others post on the car sites. While this provides many benefits, the guys who think it will be plug and play vs a carb are disappointed.

I know running a carb I will have to rebuild it 1-2 times during the lifespan of owning the boat, but I also like I can do this with simple tools and keep a carb kit on hand.

What carb was over flowing the fuel bowls ? I run the edlebrock 1409 have never seen this, only some dribbling after shut off (flooded on hot restart sometimes), and fuel bowls drying out if not used for a week

It was an Edelbrock 1409. With multiple people in the back of the boat, the boat would sit too low in the stern when trying to get up on plane. A slant wedge spacer for the carb would have probably solved that or I heard you can put some sort of plates in the bowls to keep them from spilling over.

 

[nola mike]

what you outline is the same as others post on the car sites. While this provides many benefits, the guys who think it will be plug and play vs a carb are disappointed.

I know running a carb I will have to rebuild it 1-2 times during the lifespan of owning the boat, but I also like I can do this with simple tools and keep a carb kit on hand.

What carb was over flowing the fuel bowls ? I run the edlebrock 1409 have never seen this, only some dribbling after shut off (flooded on hot restart sometimes), and fuel bowls drying out if not used for a week

I need to put a momentary oil pressure bypass switch on mine to prime the carb. starts first crank when warm or if used within the last few days. takes an embarrassing amount of cranking if it sits for a while. always concerned I'm going to kill my battery

 

[Scott06]

I need to put a momentary oil pressure bypass switch on mine to prime the carb. starts first crank when warm or if used within the last few days. takes an embarrassing amount of cranking if it sits for a while. always concerned I'm going to kill my battery

It doesn’t bother me that much To wire up a bump switch