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water intrusion

oldblue62

New member
Hi Guys. I am new here and to Volvo Penta stern drives. I recently bought an 86 Privateer with Volvo I/O. Unfortunatly I can't ID the model # for either the outdrive or the engine as they have been either removed or painted over. The original owner passed away, so the info I have is second hand. I think the engine is an AQ131 and the outdrive is a 270. I know with out this important info responses will be limited, but here is my problem. The boat sat unused for 2 years. I bought it, took it home checked the oil, plugs, coolant and normal things to check on a used engine. Everything was new as he had just got it ready to launch for the season when he passed away. After a good looking over and test running in a barrel I took it out for a ride. It ran very well in the river, so I went out into the sound and did some fishing. anchored up and fished for about an hour and left the motor running at idle, just to be safe because I was not real sure about the state of the batteries. Finished fishing and headed home, all was well. Temp, oil pressure and voltage all normal. ran about 15 minutes to the river at about 3800 rpm. All of the sudden the engine bogged down and stalled while running at cruising speed. Came to a stop and tried to restart. it cranked but didnt start. opened the engine cover to look for obvious problems and saw none. tried to start again and saw liquid flowing from the carb. At first I thought it was gas, but when I smelled and tasted it it was salt water. I got it home and checked the fresh water side of the system and it was still full of coolant, the crankcase oil was fine, no water. I pulled the plugs and cranked the motor over a few times and blew fountains of salt water out of the cylinders. I pulled the exhaust and intake manifolds off and there is salt deposits in both and obviously the cylinders were full. The only place that I can think that so much water could come from would be the exhaust system filling up through the riser elbow and getting to the top of the head and going in to the cylinders through the valves. The exhaust manifold does not have any major faults, I did the acetone pressure test I saw on this forum. So my question is how could I get so much water into the engine so fast?
 
.................................... ran about 15 minutes to the river at about 3800 rpm. All of the sudden the engine bogged down and stalled while running at cruising speed. Came to a stop and tried to restart. it cranked but didnt start. opened the engine cover to look for obvious problems and saw none. tried to start again and saw liquid flowing from the carb. At first I thought it was gas, but when I smelled and tasted it it was salt water.

I got it home and checked the fresh water side of the system and it was still full of coolant, the crankcase oil was fine, no water. I pulled the plugs and cranked the motor over a few times and blew fountains of salt water out of the cylinders. I pulled the exhaust and intake manifolds off and there is salt deposits in both and obviously the cylinders were full. The only place that I can think that so much water could come from would be the exhaust system filling up through the riser elbow and getting to the top of the head and going in to the cylinders through the valves. The exhaust manifold does not have any major faults, I did the acetone pressure test I saw on this forum. So my question is how could I get so much water into the engine so fast?


Wow....... with you having explained that all was going well while cruising @ 3.8K rpm when this occured, I'm not sure what I'd suggest other than a timing belt failure!

Here's a mental shake-down list:

..... I'll put the timing belt indexing near the top of the list.
..... this engine's intake system is Port side with the exhaust on Stbd side.
..... there is NO exhaust Riser on this system.
..... spent seawater enters the exhaust mixing chamber just prior to the rubber exhaust coupler.
..... @ 3.8k rpm there would be NO wage surge potential.
..... a failing head gasket does not typically cause an issue this abruptly.



Look up the timing belt "Indexing" specs for the Volvo Penta OHC 4 and check your belt/cogged pulley arrangement indexing.



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Hopefully you did not get salt water into the crankcase the engine will need to be fully torn down to remove all the salt and as quick as possible. Definately pull the heat exchanger and check the timing belt by putting the notch on the cam sprocket in line with the notch in the dust cover behind it then look at the timing marks it should be TDC. I would also pull the head and clean the salt water out of the cylinders and valves as quick as possible it is rusting as we speak. Let us know what you find out it is likely the AQ131A with the 270 drive the only real difference is the size of the main journals on the crank.
 
My take:

If it was the timing belt, replace it and make sure that it is properly indexed. Replace the belt tensioner at this time as well.

If need be, change the oil and filter, and get it running and up to temperature on a potable water supply (water muffs) as soon as possible!

Check the oil again.




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I`m just trying to picture how the timing would cause the flow to go backwards the exhaust valves would have to be open on the intake stroke and the intake valve would be open on the exhaust stroke it would have to be just right so the engine did not hydrolock and bend a connecting rod. It is a non interference head so the valves should not be bent. A compression test would be in order if you get it running.
 
Thanks guys. I'll check the timing belt indexing. I thought it might be an AQ131, but it has an oil cooler. The partial book that I got with it says the 131 doesn't have one. I also think it may have started life with dual carbs. I have the intake and carbs with the dual linkage. Maybe a 151? I took both manifolds off right after it happened and filled the cylinders with Mystery Oil. Going to put it back together tomorrow and try to run it in a barrel. I tried the muffs but the ones I have don't fit so well, so i cut off a garbage can and fill it with water. No water in the oil, but I'm changing it anyway. A head gasket would leak the fresh water side of the cooling system, right? How would saltwater get to the head gasket, unless the heat exchanger was bad. Isn't that the only place to two systems come together?
 
Thats what we are trying to determine what happened. The only way raw water can spit back out the intake is if the flow of fluid is backwards through the cylinders. From exhaust to the intake instead of intake to exhaust. Air and air fuel mix is considered a fluid. It has to be going backwards to spit water out of the carbs.
 
If you get it running and it passes a compression test consider your self a lottery winner. BTW it could be a AQ171 also had the oil cooler.
 
If you don't mind...... let's back up a bit!

Please post a few photos of this engine so that we will know more about our topic!

When did this occur....... Recently, or a while back?

If recently, I will suggest that you spend your time and energy getting the engine fired up. Stop tearing it down...... fire it up!
The longer that it sits ....... the further time is against you!

If the oil is clean now...... fire it up and change it later.
This engine needs to see operating temperatures as to boil out the moisture.
The salt will need to be carried out by oil changes and just plain operation.


If this occurred months ago....... you may have missed an important oportunity!


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Here is my opinion on these motors for salt water use. Not good!

What happens is the the raw water pump will start leaking at the rear seal and spew saltwater all over the timing belt and pulleys. You won't even see it because it only happens when the motor is running higher RPMs and leaks behind the pump. This in turn causes rust and corrosion on the T-belt pulleys which in turn chews up rubber T-belts like starving children at a Thanksgiving dinner. I've had this happen on all three of the VP OHC 4 cylinder boats I've bought.

You can buy an inexpensive belt and tensioner pulley at NAPA, you don't need Volvo Penta just ask for a mid 80's Volvo 244 non turbo. Get a good quality one. I'm not sure how you got seawater inside the cylinders except maybe your exhaust flapper is missing and the sudden stopping forced the water up into the motor. If this happened count yourself lucky as I don't think the motor would've hydro-locked at that point since it wasn't running. Curious, when you tried to restart the motor, did it sound different? Like less compression, maybe spun faster than normal? If so my guess is definitely the T-belt teeth were sheared off and the whole motor is out of time.

I would start by removing everything from the front of the motor to the t-belt to check timing. Cooling system, alt belt, alt belt pulley, timing cover, raw awter pump, etc. It will need to be removed to replace it anyway. When I take off all the cam and counter shaft pulleys, I use a brass wire wheel on my grinder and clean as much corrosion off of them as I can before putting a new belt on. The tensioner I got from NAPA also came with a new tensioner spring so just clean up the tensioner bracket as best as you can. Use a lot of anti corrosion grease when putting bolts and nuts back on to fight saltwater corrosion. Also when installing a new timing belt put a bit of force on hte tensioner before tightening it down. The manual with tell you to let the tensioner do the work but I find it's just not tight enough. The belt will flop around at the counter shaft pulley and can skip teeth and throw your timing off. Also you may try and rebuild the raw water pump. You can get a complete kit with new shaft and seals and impeller for about $70. A rebuilt raw water pump with cost closer to $200.

Anyway this is just my $0.02 I've learned more about these little motors than I ever wanted too!
 
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