High Temp - Plane only - (39)86 2550, AQ260, 275 drive-gctid380815

[Guest]

Just splashed the boat and had no problems at the dock, or previously when run on land. (rubber maid tote)

At the dock, I'm getting water to the impeller with good pressure. No blockage on any of the hoses leading into and out of the top water housing. No thermostat, so not the issue.

When I increase rpm's and come up on plane. I get a rapid rise in temp. I'm also hearing a louder exhaust note than usual. Throttle back down and the temp drops quick.

Does this sound like a water pick-up issue in the leg?

My next step is to run a piece of clear hose before the raw water pump to get a read on water flow and bubbles, etc.

Thanks in advance for your help.

[2850Bounty]

I'm going to suggest that your water neck fitting has failed.

Once up on step, this part rises above the water line, and if one has lost it's seal, it will want to pull air into the system.

The lack of cooling water is why your exhaust appears to sound louder.

This fitting needs to be on your list of "wear items" and must be routinely replaced..... more frequently if in salt water.

Here's what I'd do since the high temp occured. (remember... no short cuts to this! It's too dang important!)

Pull risers and check the interior of the riser couplers..... you may have blistered them.

Replace the water neck fitting and special beaded gasket. (bead faces down).

Replace the lower pivot tube O-ring.

Pull the impeller and examine it. Replace if questionable.

Look at the two thrust surfaces and the cam. If worn, replace the pump.

I take this to be a Raw Water cooled engine.

DO NOT operate without a thermostat.

The thermostat is required for good reason.

Not only does this control engine temperature, it plays an important role in the design of the T-stat housing regarding how cooling water is diverted and sent onto the exhaust system.

.

[Guest]

Thanks Bounty,

Impeller looks good, checked yesterday and bought a spare just in case. This is a new Johnson pump last year,

I caught the temp rise immediately and limped it back. Temps never above 180, so I doubt there is blistering, and it really never overheated.

T-stat, I hear you. There probably hasn't been one in there for 10+ years if I had to guess, and no issues. I've owned it 3. Is 160F good?

Raw Water

So it sounds like I need to have it pulled, yes?

Water neck and gasket, and lower pivot tube O-ring.

Does any part of the leg have to be removed? I haven't done any lower unit work yet. Is there anything else I should replace while this is apart?

Off to do some research.

Thanks again.

[2850Bounty]

If this engine does not have a thermostat installed, and yet operates within a reasonable temperature range....., there is a likely chance that something within the spent sea water side is restricting flow.

IOW, something that is causing your engine to run close to normal temperatures in the absence of a thermostat.

I can't emphaize enough re; the importance of a thermostat being installed.

If this means taking your entire cooling water system apart and looking at every aspect of it: suction hoses, supply hoses, manifold to riser transfer ports, exhaust couplers being clamped over the rise outlet "scallopped" areas (this is a big one), sea water pick up area, even crustacians in the lower unit, exhaust flappers within the bellows,....... etc........., I'd sure do it.

Understand that this boat came OEM equipped with a thermostat installed.

You need to find out what is causing this, IMO.

Ole Murphy is always just around the corner and waiting.

[Guest]

It runs 175 steady. That's assuming the guage and sender is accurate.

So how far do you think I'll have to dig into the drive. Transmission, lower unit, intermediate?

Please say none of the above.....doubtful.

Thanks.

[2850Bounty]

I have removed crustaceans from the pick up area in these lower units. These fall to the bottom when no water is being pulled in. But they rise to the top and stop when water is being pulled in. They are very restrictive.

Some hoses can become delaminated internally.

Manifold to riser transfer ports can also become very restricted when rust builds up within them. These are easy to clean out.

Riser rubber couplers often become compressed into the scallopped areas.



These couplers are always too short when purchased from Volvo Penta, Sierra, etc..... causing a person to place one of the two clamps directly over the scallopped area.

They work just fine for the first year or so...... until the material eventually becomes compressed into the scallops.



The fix: new 95mm hose approx 2" longer than the OEM and the band clamps moved higher up the riser snout.

Your T-stat housing may not be Volvo Penta. Perhaps post a photo.

Your sea water pump is a semi-displacement pump.

You can restrict outgoing flow, and the pump won't care because the vanes are flexible.

As long as she's wet, no pump or impeller damage will result.

The list could go on.... you just need to take a look at all areas.

Each system is unique as to where a restriction may be.

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[Guest]

OK,

So, remove couplers and hog out the inside to remove corrosion, then reinstall and replace the 95mm hose which is usually too short from Volvo, being sure that the clamps are not on the scallops.

It looks like the water neck could be R&R'ed with all drive components/trans in place? Yes? I hear your thoughts on it being easier to remove with the trans removed, and will consider this at time of repair.

I'm still trying to find info about the lower pivot tube o-ring.

Thanks again.

[2850Bounty]

Yep... you got it!

Give that a try..... it's worth doing for peace of mind.

Look here for the various drive components and go to Intermediate Housing and find the pivot tube O-ring p/n 941820.

If the upper pivot tube bushing p/n 814388 is bad, the water neck beaded gasket will fail soon after installation.

BTW, what water are you boating in? This will make a difference as to the thermostat temp rating.

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[Guest]

OK Thanks.

So just to confirm, I could replace the water neck and beaded gasket without removing any drive components. But it's a pain.

As for the 941820 O-ring, do I need to remove any drive components?

This could be a huge difference in cost of pulling the boat and/or just finding a lift.

Thanks.

[2850Bounty]

Well, I normally kill a few birds with the same stone..... bellows, bearing crosses, etc.

So yes, I pull the transmission for this work.

Watch for the shims.... one or two can stick to the bearing, and you may not notice them. It's easy to have one drop off onto the shop floor, and not notice it.

The pivot tube O-ring cannot be accessd until the lower unit is removed.

7 fasteners, and it will drop down.

No shims are exposed nor lost.

The entire task requires 7 new O-rings, and one red fill plug gasket.

.

[Guest]

Thank You, Thank You, Thank You.

No, seriously, Thank YOU!

[2850Bounty]

I'll accept an Elvis thank you.