Water circulation problem

[lucky7's]

I have a 2002 Mercrusier 6.2 mpi raw water cooled engine. Recently I have developed a problem. I noticed the temperature gauge fluctuating from 160 to 190 up and down constantly while running at speed on a plane. However it does not overheat at any rpm (WOT or idle). The temp does not fluctuate at low speeds. With somebody driving the boat at speed I can crawl back and watch the water coming out of the thru hull exhaust. The left pipe blows plenty of water out. The right side will blow water out fine and then stop and then blow some more out and then stop at about 5 second intervals. This correlates with the temp fluctuation. At any speed below a plane it works fine and blows water out constantly. Ive checked the exhaust riser on that side and there appeared to be no restriction. Also i am in the process of replacing the thermostat it has never been replaced. The seawater pump is only 2 years old and I bought a brand new one not a repair kit. I am thinking the thermostat is opening and closing back and forth and even though the water supply does not need to go through that for the wet exhaust I think it is temporarily disrupting the water flow. Any one that has any advice would greatly be appreciated. Thanks Fred...

 

[Limited-Time]

Re: Water circulation problem

Sounds like the impeller is going bad. Thats the first place I'd check..........................Welcome to iboats.

 

[lucky7's]

Re: Water circulation problem

Also I forgot to say I have a Bravo 1 drive. So there is no impeller in the lower unit.

 

[Limited-Time]

Re: Water circulation problem

But you do have an engine driven (belt) seawater pump with an impeller that should be replaced every 2 years.

 

[RJLeuwen]

Re: Water circulation problem

I have a 2002 Mercrusier 6.2 mpi raw water cooled engine. Recently I have developed a problem. I noticed the temperature gauge fluctuating from 160 to 190 up and down constantly while running at speed on a plane. However it does not overheat at any rpm (WOT or idle). The temp does not fluctuate at low speeds. With somebody driving the boat at speed I can crawl back and watch the water coming out of the thru hull exhaust. The left pipe blows plenty of water out. The right side will blow water out fine and then stop and then blow some more out and then stop at about 5 second intervals. This correlates with the temp fluctuation. At any speed below a plane it works fine and blows water out constantly. Ive checked the exhaust riser on that side and there appeared to be no restriction. Also i am in the process of replacing the thermostat it has never been replaced. The seawater pump is only 2 years old and I bought a brand new one not a repair kit. I am thinking the thermostat is opening and closing back and forth and even though the water supply does not need to go through that for the wet exhaust I think it is temporarily disrupting the water flow. Any one that has any advice would greatly be appreciated. Thanks Fred...

Sounds like a volume problem, either sucking air while on plane or a blockage some where.
What happened to the old pump? Did the impeller come apart? IF so did you find all the peice's check the power steering cooler for a blockage

 

[lucky7's]

Re: Water circulation problem

I have never checked or cleaned the powersteering cooler so there might be some blockage in there. If I find no blockage there then I will rebuild the seawater pump. I dont know what else to do there must be a blockage somewhere or the impeller is going bad but it doesent overheat. Also I would think that the water flow would fluctuate equally on both sides of the exhaust but its only the right side that fluctuates. Seems weird to me.

 

[Gazza1]

Re: Water circulation problem

I think that I would pull the riser off the starboard side and check it for a blockage in the water outlet into the exhaust

 

[lucky7's]

Re: Water circulation problem

The remedy to the problem was that I had piece of an impeller blade stuck in the Y pipe that supplies both sides of the wet exhaust. It seemed to get stuck in there just right that it was blocking the starboard side only. Jeesh Its always something out of the ordinary!!