Overheating - Which Impellor to check 1st?

[Shaw]

Mercruisers 4.3l EFI TBI with Bravo 2s - approx year 2000.
Raw water cooled, boat stays in water.

The starboard engine is overheating. Which impellor should I check first? I understand that there are at least 3 (seawater, recirculating, and one in the leg?).

Also, how often do they need to be changed / checked?

 

[JustJason]

Re: Overheating - Which Impellor to check 1st?

There is 1 impellor, and it is engine mounted. There is 1 curculating pump, and that is engine mounted, pretty much intergral to the block. And that's it.
Bravo's do not have a pump in the leg, that's alpha.
You need to check the engine mounted impellors... and all related plumbing. Make sure you check the pickup for the pump. Every boat is different as to where the pickup is, and you may have to pull the boat out of the water to check it.

 

[Shaw]

Re: Overheating - Which Impellor to check 1st?

Thanks. So the re-circulating pump does not have an impellor to worry about? So, it is just the sea water pump's impellor?

When you say to check the pickup. I assume check it for any blockages? Mine is thru-hull so I will have to go for a snorkel.

Lastly, with the info I've given above (don't have serial number), any idea what part number I will need?

 

[JustJason]

Re: Overheating - Which Impellor to check 1st?

I wouldn't say not to worry about the circulating pump... but with any overheat, you always start with the impellor and work your way foward. It all depends on the situation. Is it overheating at idle but goes away at higer rpms? vice versa? or does it always overheat?
When ever you have a problem with a system, as in your cooling system, it's always best to go through the whole system.
Jump in the water and make sure the pickup isn't clogged... after that have a look at the water impellor. Depending on how bad everything is you may need a new pump assembly itself. When was the last time the impellors where changed out?

 

[chiefalen]

Re: Overheating - Which Impellor to check 1st?

Don't over look the t-stat.

Jason as always gives a well thought out reply.

Something like a plastick grocery bag could be wrapped around your water pickup.

And if your in salt water and the riser is more than 3-4 years old that could be clogged up, they last maybe 5 years.

Heat exchangers are common for clogs also.

 

[Shaw]

Re: Overheating - Which Impellor to check 1st?

Thanks for the help... A Follow up...

Took a swim and checked the inlet - it was clear. So I proceeded to take the sea-water pump off. On removing the inlet hose, a mass of sea weed 10 inches long and packed solid (looked like a big cigar or something a lot more disgusting!) was jammed in there.

The next time the boat is out of the water, I will definately fit some strainers. Unless someone has recommendation on how I could fit one with the boat in the water.

 

[JustJason]

Re: Overheating - Which Impellor to check 1st?

plug the through hull hose with a wooden dowel and hose clamp..... make sure your bilge pumps work... don't leave the boat unnatended. (as in have all the parts you need before you start the project, don't take everything apart, plug the hose, then decide to run to the store at 4 in the afternoon)

it's actually a good idea to keep a couple of tapered wooden plugs along with a small hammer onboard, through hull fittings fail all the time... especially the plastic ones.