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Mercruiser 260 not pumping water

  • Thread starter Johnathn Clayton
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Johnathn Clayton

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"I have a 1984 Mercrusier 260

"I have a 1984 Mercrusier 260 (5.7) with an alpha One drive. The boat hasn't been on the water yet this year. I've replaced almost every engine accessory because the boat has sat for 3 years: carb, distributer, coil, wires, plugs, fuel pump, water pump, temp sensor, power steering cooler, thermostat and alternator. I also put on a rebuilt lower gear housing and installed new bellows this spring. The problem is I think it's overheating. The temp gauge gets to about 160 and then will shoot up to 200 in a few seconds. I immediately turn it off. This is with muffs or submerged in a large plastic container of water. When I take the water inlet hose off the thermostat block and leave it unhooked and start the motor no water comes out of it. Shouldn't the stern-drive pump be pushing water out that hose to feed the cooling system? With the motor running water pours out of the propeller but not out of the two exhaust(?) holes on the bottom of the transom. This morning I removed the lower gear housing and checked the impeller and water pump, it appeared fine. It was new with the rebuilt lower gear housing. With the lower gear housing still off I took the garden hose and back flushed the water inlet line and water poured out of the upper gear housing onto the ground. So the path from the water pump to the thermostat is clear. Then I turned the garden hose around and flushed out the engine/manifolds then water eventually came out the 2 little holes on the bottom of the transom. So I know there is nothing stopping the flow through the cooling system and that everything appears to be hooked up correctly.

All I can figure is for some reason the sterndrive water pump isn't working but I have no idea why. With the lower housing off and the top of the water pump removed I can see that the impeller turns with the drive shaft. The key is installed in it. Is it possible the rebuilt lower gear housing had the wrong water pump installed in it? I've read something about a "pre-load pin" on the drive shaft is different than No pre-load pin. Mine has a little hole at the top of the shaft but no pin. Could this have anything do do with it? What am I missing? Thanks.

Johnathn Clayton"
 
"What about the tube at the to

"What about the tube at the top of the water pump housing on your lower unit, is it in place with the rubber grommets? Is the other tube from the upper housing going into the plastic one on the lower unit and sealing in place?"
 
thanks for the reply. The 4&#

thanks for the reply. The 4" plastic tube that goes from the pump to the upper gear housing? it appears to be in there straight. There's a rubber seal inside the hole in the upper housing and it mates up to that. But it's tough to tell since once you have the lower gear housing up and ready to go into place you really can't see it. Is there any way to check?

What "other tube" are you referring to?
 
what did you do w/th old distr

what did you do w/th old distributor? Was it a points type? I know a possible buyer.
 
YOU GUYS ROCK!!! It was the c

YOU GUYS ROCK!!! It was the copper tube. When I took the old drive out it stayed in the water pump. I assumed it was part of the new drive and didn't even realize it was a separate piece. Just went out and found it in my parts bin. That would explain why the water was draining out through the prop. This has drove me so crazy.

As for the old distributor it was for the Thunderbolt IV so no points. And besides that the boat mechanic broke off the studs for the cap and the shaft it pretty rusted. I just figured it would be easier and cheaper to buy a new one.

thanks again for the help.
 
"just a quick follow up: Took

"just a quick follow up: Took the boat out this morning and it ran pretty good. The RPM's topped out at about 3500, is that normal? And the other thing was when It was idling waiting at the ramp to load the oil pressure fell pretty low. (almost the bottom of the gauge) I stuck it in neutral and ran it up to about 900rpm and went back up to 40. Is that normal? It was only idling around 500rpm and I don't think I have the carb set right.

thanks,
Johnathn"
 
Set your idle to 650-700 RPM w

Set your idle to 650-700 RPM while in gear.

"RPM's topped out at about 3500"

You should be able to get 4200 - 4600 RPM depending on the prop pitch and the condition of the engine.
 
"Thanks for your responses. I

"Thanks for your responses. I actually bought the boat 3 years ago this fall. We stuck it in the river where it was too shallow do anything more than a fast idle. After finding some soft spots in the plywood floor I then spent the winter tearing it down to the hull and replacing all the rotten floor (with fiberglass reinforced floor, rebuilt all the interior panels, refinished the teak, made a new dash, new seats, etc. I learned more than I ever wanted to know about boat rebuilding. But I also neglected the engine during all of that so I'm paying for it now. But it's turned out pretty good. Today on the water was a nice payback for all the hard work. I now have about 10k in boat that's maybe worth 4-5k at the most, so I'm kinda stuck with it.

So to answer your question I have no idea what RPM it ran at. It was bogging at about 3/4 throttle so I'm guessing the new (rebuilt) carb needs some adjusting which is probably beyond my abilities unless someone has some easy pointers?

thanks"
 
What carb is it? 2 or 4 BBL?

What carb is it? 2 or 4 BBL? Mercarb 2 BBL has a sinble mixture screw while a Rochester has 2 mixture screws.
 
Rochester 4bbl. I see the 2 s

Rochester 4bbl. I see the 2 screws at the base. Is there a key to setting them? I've never done it.

Also I'm reading on other posts that when you set the timing your supposed to remove some wire? I didn't do that when I set it. Which wire? thunderbolt IV ignition.

thanks
 
A little help here; Johnathn n

A little help here; Johnathn needs instructions for Thunderbolt IV setting base timing mode.

Johnathn: Adjusting mixture is not difficult. Set the base timing first. Then w/engine at operating temp just SLOWLY turn one screw in until the engine begins to stumble; note the position of the screw. Turn the same screw out past the point that the engine runs smooth and continue until it begins to stumble; now turn the screw in to a point that is half way between the two stumble points. Do the same for the other screw.
 
I dont believe the IV ing need

I dont believe the IV ing needs any special wire removed???? It is a 1984 ingition with no special requirement to set timing.
Just make sure the idle rpm's are below or at 700 rpm

Hook timing light to # 1 spark plug wire as close to spark plugs as possible and set Initial timing to 6-8 degrees before top dead center.
 
Maybe I do that timing set rig

Maybe I do that timing set right. I was reading some other posts about a purple/white wire that had to be removed but that must of been for a different year/model. I'll check the timing again tonight to make sure it's right. The carb adjustment doesn't sound too bad. I'll give it a shot.

thanks!!!
 
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