Suzuki 50hp. Telltale strong at start, but fades and stops in 20 secs

[ancan]

I've got a 50hp Suzuki from -00. Telltale is strong when I start the motor, with a 1,5 meter sideways stream, but soon fades and after 20 seconds or so it's down to a trickle. Engine doesn't seem hot when running, and I've detached a hose on top on the engine and when I start the engine it soon flows water from the hole it was attached to. Bought boat and motor last year so it's a bit new to me and don't really know what to expect, but don't remember it doing this last summer.

Removed the lower unit and checked the impeller before putting the boat in the water, and all looked fine.

So:
Strong stream at start: Telltale not blocked, impeller works.
Water from cooling hose: Impeller works, water seems to flow through cooling system..

Seems OK to me but I'm still a bit nervous running without a steady stream from the telltale. Anyone got any idea what could cause this?

Thanks,
Anders

 

[99yam40]

blow some compressed air up it while having the problem to see if that moves things around some and gets the flow back.
If it does you have stuff up inside motor that is blocking off passages

 

[lakensea]

First, the telltale on that engine indicate water flow prior to entering the powerhead so blockage in the engine will not cause a diminished tell tale. However there may be blockage in the engine holder where the telltale gets its water from.

Is the swiveling tell tale nozzle in the water outlet? They have a tendency to get knocked out.

Is the thermostat stuck open? That will cause a reduction in the tell tale output.

 

[ancan]

Thanks both. Agree with lakensea about not being blockage. I took a look at the cooling system flow-chart, and the hose I loosened is the exit port from the thermostat (where there was flow). By then water have already passed most of the engine so blockage seems unlikely, and it would probably cause a stronger tell-tale-flow rather then weak.

I'll check the thermostat first, because it seems easy (don't have power for my compressor at the dock). I guess a wide open thermostat will cause little resistance, and low back pressure for the tell-tale.

My theory now is that I get a strong stream while the pump is pushing water *up* in the engine, but as soon as the downwards path is filled, the siphon effect cancels out the force needed (and back-pressure).

@lakensea: I don't really understand your question about the tell tale nozzle in the water outlet? Outlet is in the prop, right?