Motor vibration NEED HELP

[oldjeep]

Chevy distributors run clockwise

[90oldskool]

So I finally gave in and took the boat up to the repair shop(master craft dealer, not a Malibu shop in my area) . They fixed the back fire but installing 5 degree carb wedge (carb was sitting at a 11 degree angle). The raw water pump pulley was miss aligned with the belts and needed to be machined . The vibration is still present at 1500 rpm-2500 rpm. Their thinking when the " new" crate motor was installed , they did not do an internal harmonic balancer.... apparently the motor is a pre 1985 that is installed. Does all that make sense? Or could it be the cam shaft?

The repair bill is adding up fast.... any help?

[MadMan]

While it is possible for the wrong balancer to be installed, I would think it is unlikely. The external balancers are used on 400's and 383's. Not anywhere near as common as a 350. This photo shows both, external is on the left. Look at yours.

http://cimg5.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/2000x1504/80-100_4510_008c38eecc96768c94f1cf5402d9b1e9c6a95447.jpg

[90oldskool]

The shop looked up the gm stamp and it shows to be a pre 1985 motor . Which would have an internal balancer. Their though is , one was not installed. This is not the exact balancer but a quick google search shows there in an internal balancers on those years.... Should i just trust their analysis . Thoughts on it being the cam ??

http://www.summitracing.com/parts/ati-917781/overview/year/1984/make/chevrolet/model/corvette

[90oldskool]

Mastercraft just called, parts installed . Boat runs like new now . The other issue they found during the lake test was the steering cable is real TIGHT . Anyone got a write up on how to do this? Going to try to do the replacement myself to save cost...

Edited February 12, 2016 by 90oldskool

[malibuparadise]

"runs like new" is such a great ending!

[Rednucleus]

Mastercraft just called, parts installed . Boat runs like new now . The other issue they found during the lake test was the steering cable is real light . Anyone got a write up on how to do this? Going to try to do the replacement myself to save cost...

What did they end up doing to run like new.

And - what's a "light" cable? (maybe tight??)

[90oldskool]

tight**** not light . sorry . I'll get the details on the repair tomorrow when I pick her up. I got the call at work and could not go into much detail .

Edited February 12, 2016 by 90oldskool

[90oldskool]

It was the flywheel that was replaced. The flywheel in the replacement motor was no machined correctly .

[Rednucleus]

It was the flywheel that was replaced. The flywheel in the replacement motor was no machined correctly .

Sounds like you have some smart mechanics, would like to know how they figured it out. Should list the repair shop for other members in your area.

[90oldskool]

North texas mastercraft . Off 820s in richland hills tx

[90oldskool]

Hard to tell but the lip is on uneven , showing some surfaced is raised and other parts are lower. (old fly wheel)

[Steve B.]

So, it ended up being the flywheel/flex plate? If it was warped, I'm guessin' it overheated at some point, big time,

Steve B.

[MadMan]

I'm no Chevy expert, but maybe that flywheel was for an externally balanced engine, like a 400 or 454.

[90oldskool]

Have taking the boat out 3 times now in the last month . Runs GREAT! Took a 2 hour trip around the lat this last weekend , and seemed to run better and better . One thing I've noticed is , when starting i have to hold the throttle at about 1/3 the way down to get her fired up. Is this normal for a carbed motor? 

[Woodski]

@90oldskool:  Glad it is running great.  As for carb question, no, you should be able to prime and then have the engine start and idle (probably hi idle for a short time) without artificially adding throttle.  Indicates perhaps an incorrect mixture setup for cold starts.  What type of choke do you have (mechanical or electric) and is all the linkage free and working properly?

[braindamage]

Great ending. enjoy the summer!!

[90oldskool]

It is an electric choke . This is the carb that's installed. It seems to be harder to start after warm up. But runs fine once fired up so i do not think the choke is staying open. 

http://www.edelbrock.com/automotive/mc/carburetors/marine.shtml

[Woodski]

Warm start up issue may be some vapor lock, a solution can be insulating the fuel lines.  Do you see any black smoke on start up when you need to hold the throttle open, if yes it sounds like a rich mixture.

[90oldskool]

No black smoke . I hold the throttle at about 1/3 till the motor trys to start then let off the throttle and she starts up like normal. Almost like priming every time . I have a carb wedge installed (what help fix the back fire) wondering if the angle is not great enough still (5 degree wedge install).

Edited March 11, 2016 by 90oldskool

[Woodski]

As a comparison, my starting technique is to actuate the throttle (which simply activates the accelerator pump) 3 times to get some fuel down in the intake manifold.  Throttle lever back to neutral & turn the key and it starts.  My boat is sensitive to where the choke is set and the bimetallic spring is not quite linear to temperature so I have to adjust it slightly for warmer or colder temperatures (back off choke tension in colder weather) so it gets set 1 tick mark either side of neutral depending on average temperatures.  Do you have an aluminum intake manifold, if yes I have found it to be a bit more tempermental compared to a cast iron one.

The angle may not be quite enough, I recall the engine angle to be close to 11 degrees.  The carb certainly works better when level, with the accelerator pump and the primary jets all located at the forward edge of the float bowls, the fuel level at that end of the carb will be lower than ideal and it might be difficult to get the floats set correctly with the engine angled like that although it should be fairly flexible and accommodate a 5 degree incline.

 

Edited March 11, 2016 by Woodski

[90oldskool]

Yes i have an aluminum intake manifold ,and the motor does sit at an 11 degree angle , so with the wedge the carb is still siting at about 6 degrees. Ill try the pump technique my next trip out ! Thank you for the valuable input!!  

[JasonK]

old answer

Edited March 11, 2016 by JasonK

[90oldskool]

@Woodski Went out yesterday and starting was the hardest out of all the trips. Outside temp was at 50-60 degrees over the 5 hours on the water . Tried the 3 pump method- no go. Had to hold the throttle down all the way and crank for about 12-15 seconds to get motor to turn over. Had a fear to flood out the motor... Even after warm up, full throttle was needed to got started. When putting boat into gear from  neutral I had to move quickly or the rpms would drop and motor would die. So I think I need to raise the idle , but that wouldn't fix the start issue....  any suggestions? I have got the gas tank down below 1/4 tank , trying to empty tank from previous owner . I know he owned the boat for about 2 years and only had it out 3 times due to the motor issue . Could fresh gas possible solve this issue? ( stabile was added back in Nov when boat was winterized)

[minnmarker]

If that gas has ethanol in it, it is the first thing to change. It's toast.  At 1/4 tank you should be good if you fill up with non-oxy gas. Next step if needed - fuel filter.