New Motor Vibration issues at low RPMs

[texans543]

Hey group, I put in a new to me motor in a 2000 Crownline 180. I put in a 5.7 GM 638 block, I completely rebuilt the block with all new rings, bearing, and so on. The old Camshaft was use since it was the marine one. It has a crappy thunderbolt V, that I am waiting on replacement parts so I can chuck that damn thing into the lake.

My question, we took it on a water test and there is a strong vibration in the boat when in gear, The only thing I did to the outdrive was replace the water impeller, The old owner put a 26P prop on it which I think is to much pitch, would this cause the vibration? I used the over prices alignment tool to put the motor in, put in a new gimble bearing, and loaded it with grease.

Thoughts?

 

[tank1949]

Hey group, I put in a new to me motor in a 2000 Crownline 180. I put in a 5.7 GM 638 block, I completely rebuilt the block with all new rings, bearing, and so on. The old Camshaft was use since it was the marine one. It has a crappy thunderbolt V, that I am waiting on replacement parts so I can chuck that damn thing into the lake.

My question, we took it on a water test and there is a strong vibration in the boat when in gear, The only thing I did to the outdrive was replace the water impeller, The old owner put a 26P prop on it which I think is to much pitch, would this cause the vibration? I used the over prices alignment tool to put the motor in, put in a new gimble bearing, and loaded it with grease.

Thoughts?

First, RE-check plugs and wiring. The motor mounts are super strong on a V8 and can sometimes conceal a miss at high speed and only during low speeds can issues be detected. Then, if OK, I'd pull valve covers and start pulling plug wires to find the cylinder that is causing issues. Perhaps valves were not adjusted correctly. Be sure that you have some real good rubber gloves when pulling wires. Trust me!!!!!!!

 

[texans543]

First, RE-check plugs and wiring. The motor mounts are super strong on a V8 and can sometimes conceal a miss at high speed and only during low speeds can issues be detected. Then, if OK, I'd pull valve covers and start pulling plug wires to find the cylinder that is causing issues. Perhaps valves were not adjusted correctly. Be sure that you have some real good rubber gloves when pulling wires. Trust me!!!!!!!

Hmm I am intrigued. When I did a small break in on the motor in the driveway I double checked all the valve lash, I have a spark tester so I can check all of the spark plugs that way, still a pain in the you know what. I am going to be putting in the Voyager Ignition Kit, as I hate this thunderbolt system. So maybe I am having a problem with that. I guess I will have to wait till I get the kit in. Thanks.

 

[Bondo]

and there is a strong vibration in the boat when in gear,

Ayuh,...... Welcome Aboard,..... Change the prop,.... The prop, 'n it's shaft is the only thing that is affected by shiftin' into gear,....
'n you know the 26" pitch is too big,.....

 

[texans543]

Ayuh,...... Welcome Aboard,..... Change the prop,.... The prop, 'n it's shaft is the only thing that is affected by shiftin' into gear,....
'n you know the 26" pitch is too big,.....

Yeah, no idea why he had a 26P on it, I have a 21 on order, should be here friday.

 

[Scott Danforth]

Hey group, I put in a new to me motor in a 2000 Crownline 180. I put in a 5.7 GM 638 block, I completely rebuilt the block with all new rings, bearing, and so on. The old Camshaft was use since it was the marine one. It has a crappy thunderbolt V, that I am waiting on replacement parts so I can chuck that damn thing into the lake.

My question, we took it on a water test and there is a strong vibration in the boat when in gear, The only thing I did to the outdrive was replace the water impeller, The old owner put a 26P prop on it which I think is to much pitch, would this cause the vibration? I used the over prices alignment tool to put the motor in, put in a new gimble bearing, and loaded it with grease.

Thoughts?

was the motor aligned when you replaced it?

were you operating with the drive in the tilt position?


the thunderbolt V is a very good ignition system, not sure what issues you are having.

you can get vibration if your prop is bent, however not from the wrong pitch

you can get vibration from improper engine balance, improper alignment, failing gimbal bearing, failing u-joints, operating above trim angles, mis-fire on a cylinder and a few other things.

 

[nola mike]

Is the vibration present in neutral as well?
And I'll take that TB-V off your hands for ya if you want...

 

[texans543]

Is the vibration present in neutral as well?
And I'll take that TB-V off your hands for ya if you want...

Ha! I pulled it and it’s not even what I thought it was. It’s for a 7.4 bravo. I am not sure if that’s why I was having timing issues. I am the 3rd owner. I am posting on eBay to see what I can get for it.
The vibration is only in gear. All compression is good. I am waiting on some parts to take care of others items and for it to jot be a million degrees outside

 

[texans543]

Is the vibration present in neutral as well?
And I'll take that TB-V off your hands for ya if you want...

was the motor aligned when you replaced it?

were you operating with the drive in the tilt position?


the thunderbolt V is a very good ignition system, not sure what issues you are having.

you can get vibration if your prop is bent, however not from the wrong pitch

you can get vibration from improper engine balance, improper alignment, failing gimbal bearing, failing u-joints, operating above trim angles, mis-fire on a cylinder and a few other things.

All new gimbal bearing, u-joins looked okay. I think a misfire could be possible but it’s only doing it in gear, that’s my concern. I am going to pull the out drive and check the alignment again. It could have shifted or something strange. I did check the alignment 10 times but who knows. As far as engine balance. I did what I could in my home shop. All pistons went back into their hole thy came from.

 

[Rick Stephens]

What was for a 7.4L Bravo?

If in doubt, always replace u-joint crosses. They can be bad and virtually impossible to check without disassembling them. If you pull em, easier to replace than to decide they are (probably) good and reassemble.

 

[texans543]

What was for a 7.4L Bravo?

If in doubt, always replace u-joint crosses. They can be bad and virtually impossible to check without disassembling them. If you pull em, easier to replace than to decide they are (probably) good and reassemble.

Whoever put the last motor in Put this module in. I looked up the specs and it’s the wrong timing curve for this motor.

I saw the u-joint conversation today. I might do that since they are cheap.

 

[tank1949]

What was for a 7.4L Bravo?

If in doubt, always replace u-joint crosses. They can be bad and virtually impossible to check without disassembling them. If you pull em, easier to replace than to decide they are (probably) good and reassemble.

Indeed! I had a 1995 Chevy truck that I maintained, including greasing U joints. Grease was not getting to rollers. Weird. I notice slop during inspection and decided to pull. I was shocked at no grease. .