View Full Version : engine vibration 1994 prostar 190
07-07-2013, 08:58 PM
I have a 1994 prostar 190 with a 351 cu in ford v8
When I put it in the water I had a large vibration. Pulled out the boat and found one blade of the prop was missing a half inch. Replaced prop same vibration. Cutlass bearing had some slob. Replaced bearing and checked shaft.
Still had large vibration. Removed belt around alternator ,water pump and crank shaft. Vibration for the most part disappeared. When manually turning water pump no noise heard.
Any ideas what is causing the vibration?
07-09-2013, 11:32 PM
checked the belt and found it had worn down about 30 %. put new belt on and vibration mostly disappeared until put engine under load by pulling tube with two people. vibration returned. when not pulling and just cruising vibration almost gone. any suggestions?
07-10-2013, 11:01 AM
Have you checked the shaft for straightness? You may have a slightly bent shaft. Considering that your prop was sheared and your cutless was loose, I would say there is a good chance that your shaft is bent.
Did you swap a motor into that hull? In '94 the oem efi engines where 270hp Chevy 350 or Chevy LT-1(corvette). Jamie
07-10-2013, 11:18 AM
You should check the prop shaft alignment with the flange on the driveshaft from the transmission as well as straightness of the prop shaft itself. It is easy to check for straightness just use measure as a reference and rotate the prop shaft. It it does not change the shaft is straight. If not, well its bent.
The alignment is a little more involved. You will first disconnec the propshaft from the driveshaft at the flange and remove the bolts. Then, separate the flange enough to see light. Use a feeler guage to measure the gap at the 12, 3, 6, and 9 oclock positions. They should all be within .003 inches of each other. Then, rotate the shaft 1/2 turn and repeat the process. If there are variences in the gap then you have to adjust the engine/transmission mounts to achieve the proper alignment by making one or more higher or lower and/or pushing the fron/back from side to side.
When you get it straight it is best to recheck when the boat is on the water after a day of use. This will confirm that your alignment is proper.
Misalignment will cause vibration. It reduces engine efficiency, robs power, and leads to wear and tear.
07-12-2013, 09:35 PM
shaft was checked by boatyard when they installed the cutless bearing and was perfectly straight. Is it possible that a misfiring under load that is causing the vibration? I removed the distrib cap and there was corrosion on the contacts. I will replace tomorrow.
07-13-2013, 01:51 PM
let us know if that helped...
07-13-2013, 05:02 PM
I inherited the boat from my son. It turns out it is a 1992 not a 1994. The engine is a Indmar 351 cu in. Having trouble finding a replacement dist cap from three auto parts stores.
Anyone know what car dist cap will fit?
08-06-2013, 05:55 PM
Might be worth doing a compression check. We had excessive vibration and it turned out the gasket had blown on one side. Changed both cylinder head gaskets as well as the dist cap for good measure and it's fine now