Volvo penta 2002 raw water flow problem

[brale]

Hi everyone.
I keep having an annoying problem on my Volvo 2002 MD on my sailboat.
About a month ago I noticed that after some time of motoring there was no water flow on the exhaust. I immediately stopped the engine and first thing I did was change the impeller although the old one didnt look bad.
It solved the problem but only until my next trip when the problem repeated.This time, after sailing for a while and starting the motor - again no waterflow.
Since then I did all of these things:
checked all seawater pipes and found a small piece of impeller in one,
tested the thermostat (OK opening on different temps) and changed its gasket,
flushed the whole seawater system with HCL acid - many nasty water came out,
put off and cleaned the exhaust elbow (was dirty but not fully clogged),
made a partial rebuild of my raw water pump because of little oil leaking (new shaft kit, orings and gaskets)
When motor starts cold the water flow is good, after driving for a while or more hours and restarting it is also good, but after sailing and then restarting it sometimes (not always) doesn't flow out on the exhaust.
Except the first time, I am pretty sure that this happens only after sailing. Then I have to restart my engine once or twice and then it starts flowing out again.
What to do next - I am thinking of removing head and mecanical clenaing of all water passages) (not sure if that is necessary), or buying completely new water pump.
Any other ideas?

[Bambolera]

You might be getting air in the raw water line. Does your through-hull come out of the water when you sail?

[brale]

Originally Posted by Bambolera

Does your through-hull come out of the water when you sail?

Not sure that is possible. I have a saildrive SD120 and the cooling water inlet is on the SD leg in front of the prop.
I really do like good closehauled sailing on the side , but am pretty sure the water inlet is always in water

[colemj]

Is it possible a barnacle has broken off in there and is rattling around sometimes being sucked up against the intake?

Mark

[brale]

Originally Posted by colemj

Is it possible a barnacle has broken off in there and is rattling around sometimes being sucked up against the intake?

Mark

Few days ago I was diving below the boat for checking the zincs and the intake hole is absolutely clean.
I have never checked the space between the intake hole and seacock but nothing larger cannot enter inside

[brale]

After the exhaust elbow the exhaust hose goes into the plastic gooseneck and then the exhaust hose goes further to the exhaust/water outlet.
What is the function of that gooseneck? Is it only for not letting the water go back to the exhaust or it has more functions?
I haven't removed and cleaned that gooseneck, can it be clogging the waterflow?

[egbarrer]

Originally Posted by brale

Few days ago I was diving below the boat for checking the zincs and the intake hole is absolutely clean.
I have never checked the space between the intake hole and seacock but nothing larger cannot enter inside

I have the same problem in my volvo 2003. The intermitent clog was in the seacock. I disconnect the hose open the seacock and pass a flexible wire. A lot of water came in and some barnacles and i have good flow again.

[Vasco]

I used to have the same problem with a 2003. It seems the raw water intake impeller loses its prime when heeled during sailing. Sometimes it'll come back after a while (when it goes you hear a hollow sound from the exhaust) sometimes I had to close the through hull and prime the line through the strainer, reopen the line and start.