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90oldskool

Motor vibration NEED HELP

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90oldskool

Just boutht a 1990 skier , which the seller said had a new rebuilt motor installed last season . This is the first boat i have bought. When looking at it to buy , the motor had a pulley that was shaking pretty hard (lower left pulley) and asked the guy what was wrong with the pulley . " i have know idea". Thinking it was just a bad bearing , I went a head an bought the boat. After a trip to a local shop, timing checked, timing chain checked , fire order checked they still can not get the vibration to go away , and think it may be the cam shaft and WANTED to pull the motor to explore . I refused to let this shop complete. There is a carb backfire when giving full throttle as well. the motor is a GM 350 year 1993. Any thoughts on what this could be ? Vibration happens out of water , with the boat in neutral .

CORRECTION: it is not the crankshaft pulley

Edited by 90oldskool

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oldjeep

Is the "lower left" pulley still vibrating? If so, what is it attached to?

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90oldskool

yes it is still shaking , and by online diagrams that pulley is the crankshaft.

CORRECTION : pulley is for raw water pump

Edited by 90oldskool

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Rednucleus

any chance we could see a short video?

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GreenMan

If the crankshaft pulley is visibly vibrating, doesn't sound good...

Given the era of the boat, could it be a Mercruiser engine and the lower left pulley is the water pump?

Here's the Mercruiser in my old 1993 Gilflite and the lower left pulley on driver's side of ski pole is the water pump.

DSCN0673_zpsvqj6lmsr.jpg

Edited by GreenMan

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GreenMan

Sounds like a good call to remove the boat from that workshop. Wanting to pull the engine to check the camshaft is likely a little odd. If the cam had some fault that results in severe engine vibration, pulling the valve covers and rolling the engine over will quickly determine if there is a worn out lobe or some other issue that prevents a cylinder from working or whatever...

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Dare2goBare

As per GreenMan, lower left pulley would be the water pump. Crank is always dead centre.

If in fact it is the crankshaft pulley that is vibrating, you unfortunately have a major issue.

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REW

Is that the raw water pump?

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GreenMan

If it is the crankshaft pulley that's vibrating, it may have failed damper rubber presuming it is a harmonic balancing pulley?

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90oldskool

It is not the crankshaft. Can not get a video till the weekend .will try to post a picture when I get home . Motor looks the same as chief's photo

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Woodski

@oldskool: you mention running the boat out of the water, when doing that you need to make sure you have a water source supplying the raw water pump (the item noted low on the engine and behind the captains seat) or you will destroy the housing and impeller. In addition you will overheat the engine. If you are doing dry land running I assume you have a fake-a-lake connected. I am also curious on the comment on checking the timing chain, if that is the case they should easily be competent enough to check the cam at the same time, did they tell you what specifically they did? If a cam swap is needed, it can be done in the boat, you simply have to slightly twist the engine and it will slide by the pylon. Also, the cam is a marine cam, not a standard automotive one, it has specific lift/duration specifications.

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Dare2goBare

It is not the crankshaft. Can not get a video till the weekend .will try to post a picture when I get home . Motor looks the same as chief's photo

Glad to hear, hopefully something straightforward once isolated!

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90oldskool

I can not figure out how to post a photo...


Yes a water hose was connect to the motor when running boat out of the lake. The shop I do not think was competent to be trouble shooting this issue. Reason I took the boat into this shop was the thought it was only in need of a carb adjustment to correct the backfire. The shop also said I needed a new carb , that the edelbrock that was installed was an automotive and was dumping fuel; so the shop swapped it with a 450cfm quad jet(in hopes of selling me the carb), which made the boat barely start and run even worse . This is when I asked them to please reinstall my carb and return my boat.


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Rednucleus

Left of pylon in that view is raw water pump. As said above, if crank or cam, has to be one of the center pulleys doing the wiggle. Could also be a loose pulley - had a loose crank pulley on our 93 suburban and boy did it get a wiggle on! Based on your description though you probably just need a new water pump.

Edited by Rednucleus

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90oldskool

Just looked up my carburetor on the edelbrock website . model 1409 is a marine carb. Now I am convinced the shop mech had no idea what he was talking about !!

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mikeo

Let the crew know where you're located, someone here might know a good mechanic or shop nearby. There are some very competent people on the site too, and one of them might be able to help you diagnose the problem in person.

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tvano

i'd run that engine without a belt on it for a short period of time.

if that pulley spins and vibrates i'd pull the pulley next, and run it again, to see if the pulley is bent or look for a wobbly crank

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90oldskool

I'm located in Watauga ,TX (Fort Worth). I took a few photos of my set up but can not get them to upload. I'm on a truck forum and use photobucket.com but can not get them to work on here... As some stated that lower left pulley to be the raw water pump , looking at it last night -they seem correct. On the back side of the pulley is the water pipe that then runs the length of the boat . The shop discredited my carb and intake to the incorrect size/type. On edelbrocks site , the 1409 carb is a 600cfm marine carb and the performer 2101 intake manifold is correct for that size motor and carb. Expensive lesson learned , but I'm still at square one . Vibration from the motor and back fire when giving full throttle . Once the backfire clears , motor runs strong and climbs to high RPMs . Any local shop recommendations would be much appreciated. I did look at a few shops and read reviews; one appears to be good, with lots of good feed back from clients.

Supporter: I had the thought of removing the belt to see if the vibration quite, did not think it was a good idea since the water would not be running to the motor - fear of over heating. Once again this is the first boat I have own; would the water pressure from the water hose be enough to push the water through the motor to keep it cool for a short test run?

Edited by 90oldskool

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tvano

Supporter: I had the thought of removing the belt to see if the vibration quite, did not think it was a good idea since the water would not be running to the motor - fear of over heating. Once again this is the first boat I have own; would the water pressure from the water hose be enough to push the water through the motor to keep it cool for a short test run?

w a belt driven impeller, which is disconnected, i would not expect over heating with a 10 second run cycle on a cold engine.

no need to run anything but idle and you won't need but 3 seconds to determine if that pulley or crank has been damaged.

keep in mind that the hot exhaust gasses will not be water cooled (as oem designed) when running in this fashion and will cause the inside of the rubber exhaust hoses to over-heat/melt a bit but i would not expect any significant damage. leaving the water source on and forcing water through the block may help/can't hurt.

keep it short.

none of the above is necessary. your crank pulley isn't bent. that's the raw water pump you've labeled as 'bad pulley'.

remove just that raw water pump pulley, fit your garden hose to run cooling water into the hose that exits the raw water pump and vibration test w engine run.

Edited by tvano

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oldjeep

Take the belt off the raw water pump and spin it by hand - also wiggle the pulley side to side to see if either the bracket is loose, bushings are shot. Regardless, neither would have anything to do with your running problems. for the running problem, the first thing I would be doing is check the timing yourself - making sure that whatever distributor you have is in base timing mode (whether that be electrical or vac)

Now have you ever run this boat in the water under load? If not then I would also check if the distributor is 180 out. It is possible for an engine can run with no load on it in that state and can actually behaves like you are describing - low RPM stumble/backfire and then will rev up.

Also check that there is actually power to that electric choke when the key is on and the choke isn't running wide open all the time.

There is some pretty goofy looking plumbing in that boat too. The "custom" welded aluminum u turn doesn't look stock and that plastic water valve looks added on too.

One more thing - is that fuel filter plastic? Or am I just seeing a reflection in it?

One more one more thing ;) I'd make sure that clear hose is actually heat rated - the stuff on the raw water side is no big deal but the piece on the tstat housing is concerning.

Edited by oldjeep

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t a

I'm watagua area also, where did u take it the 1st time?

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90oldskool

Thank you chief for the pointers , I will remove the belt and give her a spin . My mech that does all my truck work is coming by this weekend : I'll have him check the timing and distributor(i'll show him your response) . The shop said he set it to 8 degrees but I do not trust that .

Shop was Finely's total restoration off 28th st . The new shop with good reviews is off boat club road called " boat doctor" -this is the shop i'm considering taking it to.

Open to suggestions if you know of a good service shop in the area, would like to get established with a shop that i can have services done at yearly . Most shops that i called in the area do not service the older boats is what I'm being told .

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90oldskool

Going to do some trouble shooting today; Can anyone suggest a way for me to find out if my distributor is clockwise or counterclock wise rotation? The belt rus clockwise , wanting to make sure the firing order is correct....

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