Belt pattern on 1987 Aquasport 290 TM twin merc crusier 350"s

[Jim Hodge]

I popped a belt on my port side engine. we replaced it and now the water pump pulley doesnt work. Is it because the pump is bad or is the belt the opposite way then the starboard side.
i do not have a manual for the boat

[fitz73222]

Port engine may run backwards compared to the starboard engine. Try running the belt opposite to what it is on the starboard engine. In other words if the belt runs on the top of the pulley on the starboard engine, run the belt to the bottom of the pulley on the port or vise versa. Try cranking the engines and observe the rotation. Many twin inboard set ups have one of the engines running backwards using a cam with 180 degree off valve timing.

[Jim Hodge]

Thanks

[fitz73222]

I did assume you are running a serpentine and not a V belt otherwise my suggestion will not work.

[GoneFission]

Are these original 1987 Mercruiser 5.7/260s?  I think they had v-belts until the '90s.  The earlier ones with v-belts have two or three belts, one for the alternator, another for the water pump, and a third if power steering is installed.  Here is the earlier one with v-belts:


Here is the later one for reverse rotation with a Serpentine belt:



There were several variants depending on power steering, etc. - notice E and F are normal roatation, and G and H are reversed:
 

 

Fitz is right with reverse rotation engines, but Mercruiser just reverses the inlet and outlet of the seawater pump for reverse rotation.  This would not be affected if you did not remove the seawater pump - if you removed the pump and got the hoses reversed, the pump still will work, but it will be pumping air, not water.  The inlets and outlets on the seawater pumps are opposite for reverse-rotation engines.   

Hope this helps - good luck! 

[Jim Hodge]

Thanks everyone for responding.  I found out the engines are 2002 350 merc cruisers. Sorry for misleading , but we didn't know. We just purchased the boat two months ago. We thought the previous owner said he rebuilt them in 2002.