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#568485 - 07/12/17 01:49 AM Re: Over heating 350 Merc MPI Bravo 2 [Re: Boatbottom]
Boatbottom Offline
Lieutenant Commander

Registered: 10/24/14
Posts: 79
Loc: Upstate NY
Hi All! As much as I would like the problem to be gone, it's not. Next on the list would be a problem on the suction side of the pump. The boat will have to come out of the water for this. My little economy car won't tow it so I'm waiting for a friend with a pick up. It will be a while before this happens.

Just for entertainment, I'll explain the the engine seems to be just fine, with no overheating at 1800 rpm. so....I've been cruising at at 1800rpm. At least I've been on the water.
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#568533 - 07/15/17 03:29 PM Re: Over heating 350 Merc MPI Bravo 2 [Re: Boatbottom]
WayWeGo Offline

Registered: 08/26/05
Posts: 2226
Loc: Oakton, VA

There are some things you can do on the suction side without pulling the boat out of the water. If you remove the hose going to the suction side of the pump, you can try blowing through it to see if there are any obstructions. If you are not able to blow hard enough to get bubbles to come out at the drive, you might be able to use a vacuum (with the hoses switched) or compressed air. This works well if there is a plastic bag or debris in the water passages.

Also, you can get in the water and inspect the outdrive to see if there is anything visible in the water intake area of the drive.

1975 Trojan F36 Convertible, Twin Chrysler 440's
2014 West Marine AL360 Inflatable, 1966 Mercury 6HP, 1992 Mercury 20HP

#568592 - 07/25/17 10:52 AM Re: Over heating 350 Merc MPI Bravo 2 [Re: Boatbottom]
Boatbottom Offline
Lieutenant Commander

Registered: 10/24/14
Posts: 79
Loc: Upstate NY
The saga continues, pulled the outdrive and found shell pieces in the water passage. Cleaned that out along with the passage through the transom. Put it back in the water, idled the boat for 1 hour, in gear, and it was fine. Went for a ride went up on plane and seemed fine. As I was returning to the dock it overheated. So...I guess I wil continue the search.
No Blunder goes unwitnessed

#568594 - 07/25/17 01:36 PM Re: Over heating 350 Merc MPI Bravo 2 [Re: Boatbottom]
tpenfield Offline

Registered: 08/29/05
Posts: 2213
Loc: Cape Cod, MA
Were the shell pieces (barnacles, etc) in the lower unit portion of the outdrive, or were they caught in the inlet hose that attaches to the bell housing? The thing about salt water use is that things can grow in the lower unit passages and continually dislodge and get stuck in the inlet hose at the bell housing . . . so unless you got everything cleared up and all shell debris emptied from the outdrive before you put it back on, then more 'stuff' could be collecting up at the bell housing and reducing the flow.

If that all seems good, 'we' did not check the oil coolers (engine oil and power steering fluid coolers) that are after the sea water pump and before the thermostat housing, IIRC. Those inline coolers can get clogged with sea weed and marine life debris, and restrict the flow.

You will want to open up the hose on the inlet side of those coolers and see if you got a clump of 'stuff' or anything blocking the flow.

Final thing (if it gets that far) is to check the condition of the water passages in the exhaust manifolds and elbows. Those can get blocked up with rust scale, which reduces the overall flow of cooling water through the engine.

Edited by tpenfield (07/25/17 01:37 PM)
Regards, Ted

Formula 330SS

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