1984 sea ray 7.4 mercruiser overheats

[grumpy armenian]

I've just bought a 1984 sea ray srv260 with a 7.4 litre engine. engine was overheating under load even at idle speed. At idle on the dock, temp was on 1/2. After some investigation, found out that on bravo one outdrives the raw water pump is on side of block. Replaced pump & housing, the impeller was no more, it came apart. The previous owner said they kicked up sand & overheating began when they were wide open throttle. So replacing the impeller & housing should have fixed it but the same symptom exist. Still the same scenario, still not enough water circulating through the block, took off hoses from the thermostat housing & the flow was sporatic at best. Head gaskets????Need ideas please. Thank you.

 

[bomar76]

Re: 1984 sea ray 7.4 mercruiser overheats

All the parts from the dead impeller blocking power steering cooler and oil cooler.

Blocked/corroded manifolds and risers.

 

[cr2k]

Re: 1984 sea ray 7.4 mercruiser overheats

You MUST find ALL the pieces of the old impeller or you will always have heating problems.

 

[grumpy armenian]

Re: 1984 sea ray 7.4 mercruiser overheats

Found all of the additional missing pieces of the impeller were in power steering cooler. Thanks guys, I'm new to boating & this boat so far is giving me a crash course in cooling systems

 

[grumpy armenian]

7.4 bravo one not getting enough sea water

7.4 bravo one not getting enough sea water

I've replaced the raw water pump & had good flow for a day or two. Now it seems like not enough water is coming in from the outdrive. Is there another pump in the outdrive or is there a screen or something. This boad had barnicles out the wazoo, everything got scraped off, had pieces of the old impeller in p.s. cooler had that removed & very poor water flow coming into the raw water pump. Any ideas would be appreciated.

 

[marcortez]

Re: 7.4 bravo one not getting enough sea water

Re: 7.4 bravo one not getting enough sea water

Usually there are some plastic or metal water intake screens where the cooling water enters on the lower unit sides....below the cavitation plate.

That would be a good place to check for obstructions....marine growth, barnacles and such.....

 

[QC]

Re: 7.4 bravo one not getting enough sea water

Re: 7.4 bravo one not getting enough sea water

Hey Grump, welcome aboard!! I moved this to the I/O section as we keep the Boating section free of engine topics . . . You will get the most focused help over here as well.

I've replaced the raw water pump & had good flow for a day or two. Now it seems like not enough water is coming in from the outdrive.

How do you know that? What is the problem that leads you to question flow? I know it seems simple, but often people chase things that aren't causing an issue, so it might be best to start at the beginning . . .

 

[Bt Doctur]

Re: 7.4 bravo one not getting enough sea water

Re: 7.4 bravo one not getting enough sea water

This boad had barnicles out the wazoo
You could also have barnicles UP THE WAZOO too. They dont just grow on the outside

 

[QC]

Re: 7.4 bravo one not getting enough sea water

Re: 7.4 bravo one not getting enough sea water

OK, now I get it Grump. I merged these threads. Helps when we can follow something through from start to finish. Good luck with the wazoo

 

[grumpy armenian]

Re: 1984 sea ray 7.4 mercruiser overheats

Sorry guys, I'm having a difficult time navigating through the forums sometimes.I will post future stuff in the right areas. Is there a screen of some sort in the outdrive? Everywhere in engine I get good flow, if I put a garden hose & flow water backwards out of the outdrive I get water splashing in my face & water trickles out of the outdrive. I'm an auto mechanic by trade, I am just not that familiar with marine cooling systems though I realize it's not rocket science, experience still rules. Do I have to remove a portion of this outdrive to correct this flow issue or is there some other ways. Thanks.