Marinette Boat Forum

We recently purchased a 39 DC in Ft Loudon TN. We’ve spent a week aboard and another weekend working through many maintenance things. We will be back to the boat this coming weekend and plan to tackle changing the impellers in the raw water pumps on the twin 454’s.
From a casual glance and try to access them a few weeks ago when I was there it seems to be VERY challenging to access the pumps. Any advice from those experienced with this set up?
Also, is there a tensioner on the belt? Or, is the adjustment/tension via a slide type mount of the pump?
Thanks for any advice.

Never worked on those. I suggest you ask on the marine engine forum. Go to the Mercruiser section.

Jeff

I usually open the engine hatch and lay on the floor to reach the hose clamps and mounting bolts. It is easiest to remove the pump and work on it outside the engine compartment. Because of the tight quarters, be careful not to catch your sleeve/clothing or a rag on the fire suppresion halon system star wheel. If you accidentally discharge the halon system you will get seriously burned by the freon. I cover the star wheel with a cover so I can't bump it. The tension on the belt is controlled by the slide mounts on the water pump. You will have reverse rotation engines, so mark the back plate of the water pump to show which way the impeller blades need to be bent.

Paul

Thanks for the advice Paul. I’ll try what your describing when I get back to the boat on Saturday. I’m not sure my arms will be long enough to reach down to the bottom of the pump while laying on the floor….I’ll certainly try though. Will also pay attention to your advice on the halon system!

I know nothing about the motor is ques but the first owner of my 32 FBS with twin 318's stored a small area rug aboard that he placed atop the engine so he could rest on the engine to reach some otherwise out of reach parts such as an outboard spark plug and other items. I did it, too. Challenging, but got the job done.