Can't get suction through outdrive!!!

[PiratePast40]

Engine is a Volvo AQ130D and the outdrive is a 280. Just put the motor in the boat and reassembled the lower and intermediate housings. I hooked up to the muffs and no water flow inside the boat. Disconnected the hose going from the transom plate to the strainer and no water at all from the outdrive. Hooked the garden hose into the strainer line back to the transom shield and get a good stream out the bottom of the outdrive.

Nice strong water pressure at the hose and water comes out the hole in the bottom of the drive when the muffs are hooked to the inlet vents.

As far as I can tell, there just isn't anything in the outdrive that would act as a check valve. But why can I only get water to flow one direction?

 

[Maclin]

Re: Can't get suction through outdrive!!!

The hole on the torpedo needs to be blocked off while running with engine flushers. That is a drain for the water inlets and will let air in and break suction. If the engine flushers do not cover the inlet grates then that is another potential suction breaker. There is also a probability that the fitting on the outdrive that the hose connects to is corroded and letting air in and breaking suction.

If you can find a big enough tub or barrel you can try putting the outdrive into it and fill with water, make sure it is higher than the anti-cav plate then run it to see if water gets sucked up that way. If you run it for very long be sure to keep the hose running in the tub, just let it slop out so as to keep fresh cooler water coming into the tub.

If it sucks up water that way then your flushers probably just do not work for that drive, or you just needed to plug the drain hole at the bottom. This will mask the outdrive hose/fitting problem though, as it will be underwater and will not cause a problem then. However if that hose/fitting has a problem it will show up in the lake on plane, it will be above water then and could allow air in and break suction.

 

[PiratePast40]

Re: Can't get suction through outdrive!!!

Thanks for the advice. Everything you've said makes sense and I've allready cut up an old trash can for a "run bucket". I pulled off the lower unit to look for any rags, leaves, rodents, or small children that may be restricting flow. The o-ring seemed to be in fine shape so it's not a question of breaking suction at the yoke interface. Funny thing is, it started getting suction after I put everything together but then when I restarted the motor, it lost suction again. Went ahead ans installed a 't" for a hose hook up at the strainer inlet hoping that a slight positive near the pump suction will get water moving that direction next time.

 

[PiratePast40]

Re: Can't get suction through outdrive!!!

Well - just ran it again with the outdrive in the bucket. When first running, the pump gets a good suction. Put it in gear and lose suction on the outdrive. Put it back in neutral and refill back to the intake louvers - stil no joy. Hooked the hose back up to the strainer inlet side and it picks up. Will maintain temp around 160 when water is available either from the bucket or the hose so it seems the thermostat is working well.

O-ring on the intermediate to lower end is new and in good shape. Impeller is new and rotates in the housing (observation with cover off). Obviously works when it's easy to get a suction. It's a positive displacement pump so water won't get by unless the pump is working. Basically it either works or doesn't.

Next step is to look for other suction leaks. The seawater strainer holds under positive pressure (garden hose pressure) so that isn't a source of vacuum (or suction) leak.

Really don't want to pull the gearbox to get to the water inlet elbow on the intermediate section to check for a good seal. Any other ideas on how to check there?

Looks like I may be having the same problem as lilbush on the thread here so any help will probably be appreciated by both
http://forums.iboats.com/showthread.php?t=326534

 

[captmello]

Re: Can't get suction through outdrive!!!

I don't have same engine as you so I don't know if this could work but you could try, I did it on mine.

If you have a rigid tube coming from the inside of the transom, it would be attached to the s hose from the outdrive on the outside, or an alternate place would work, as long as its before the impeller.

I took an old inner tube and cut it in such a way that I was able to clamp the air valve stem along with some of the old inner tube using a hose clamp to the water intake. Duct tape the water pickups on the bottom of the outdrive and give it a little air 10-20psi and have someone listen for leaks.

Again, shadetree stuff.

 

[bruceb58]

Re: Can't get suction through outdrive!!!

You need to look at where the hose that comes from the transom area to the pump. Where it screws into the transom is a known weakness in these and may be letting air in.

Put a clear section of hose in front of the water pump and you can test for air getting in.

 

[Maclin]

Re: Can't get suction through outdrive!!!

It just about has to be between the intake grates and the hose/fitting coming off the drive. That fitting corrodes and looks ok from the outside, but take the hose off and most of it could be gone. Or it is the tube and seals inside that lead to the fitting.

 

[PiratePast40]

Re: Can't get suction through outdrive!!!

I'll just keep narrowing down the source. I should have gone ahead and replaced the water pickup housing when the drive was off. It's a little flattened but didn't seem to be in terrible shape. It's ironic how easy it would have been to replace the housing and gasket just a few days ago but now with the outdrive installed, it'll be a pain to get in to that area. Especialy since I now have the drive in a trash can filed with water so can't turn it. No choice now but to empty the tub and keep looking for air leaks.

I just spent the last hour and a half looking for a timing light. I refused to pay the outrageous prices from the parts shops and Sears. Ended up spending $30at Harbor Freight plus a bunch more in gas so probably should have spent the $40 that Auto Works wanted in the first place.

Dang - funny how your mind starts getting fuzzy at the end of the day when you're wrestling with problems from the *%$@# boat.

captmellow - like the way you come up with ideas. Sounds a little like "redneck yacht club" type of mechanics but I love it. The scary part is - it just might work!

 

[PiratePast40]

Re: Can't get suction through outdrive!!!

Just got off the phone with a Volvo technician so a little more insight into this problem.

As we've all discussed, it's obviously a suction leak and the water neck, hose connection, or gasket are the normal culprits (although the lower end gasket on the pivot tube could also be worn).

His recommendation are:
Check the water neck for cracks or see if it's corroded to the point that it could be a problem.
Check the hose fittings to make sure they are snug. If the hoses are removed, use weatherstripping adhesive to hold and seal the hose to the neck.
The gasket under the filler neck can also harden and lose the seal on the pivot tube below it. If removing the water neck - BE VERY CAREFUL NOT TO BREAK THE BOLTS. The bolts are stainless and the frame is aluminum. If you break those off, you'll pay dearly! If they don't want to move, use a torch on the aluminum frame to get some metal expansion to break the bolts loose. He says it's much easier to pull the gearbox than to try to replace the neck with the gearbox in place. He says it can be done without removing the gearbox but you may need to learn to curse in a foreign language when you use up all the words you now know!

Obviously, you would go into further depth as you look at the possible problems.

I'll work on mine later this afternoon and let you guys know what I find and how it turns out. Hope this helps others fix the problem or at least get a better understandaing of the possible causes and resolutions of the problem.

 

[int76]

Re: Can't get suction through outdrive!!!

i purchased a i/o a couple days ago and am having the same issue that it will not pump water. I am not fluent with marine terminology but understand this is a vacuum related system. I noticed that the freeze / cast plug has popped out, could this be the reason behind my lack of water being pumped?

motor runs fine and have it submersed in a bucket so water is available just not getting anything through the feed line at all.

thanks
justin

 

[bruceb58]

Re: Can't get suction through outdrive!!!

Justin,

You should start another thread with your problem. Post the exact model of your engine/drive so we all know what you have.

 

[PiratePast40]

Re: Can't get suction through outdrive!!!

Was able to resove the problem. I put a flush "t" in the inlet line to the seawater strainer and presurized the suction side from the pump out through the outdrive. Needed to hold the muffs in place and plock the hole in the botom in order to hold any pressure in the system but found the leak in the inlet hose next to the connector at the intermediate housing. Pics are below:

Replaced the hose, gasket, and inlet fitting. Works fine now and "sea trials" are scheduled for tomorow.

 

[Maclin]

Re: Can't get suction through outdrive!!!

Good work

 

[btberte]

Re: Can't get suction through outdrive!!!

I have an 125b had suctions problems problem was a gasket at the goose neck looks a little a thermostat housing from the s hose to the lower unit

I purchased a rv 12 volt pump and put it on a tee as backup I think that was better than looking for connections or gaskets.

 

[Maclin]

Re: Can't get suction through outdrive!!!

btberte,

What do you mean exactly? Do you have a separate water pickup laying the boat that you have plumbed thru the rv water pump into the raw water hose tee that you use to run it on the trailer out of the water? Or do you mean you have a separate thru hull raw water intake that is plumbed to the rv water pump to use in place of the pickup on the outdrive to feed the engine's raw water pump?

If you use it just to run on the trailer then you will not know if you will have a problem in the water. And if you cannot pick up water while in the lake then searching for leaky gaskets and hoses has to be done anyway.

If you have a separate thru hull to run from while in the water then you should not need the 12v pump, the engine's raw water pump should be able to draw it up from the thru hull unless it is a really long hose run.