I have a 89 dt55 that sets off the waterflow alarm but the telltale is strong. I replaced the impeller and plate and same thing. The top cylinder seemed very warm, I couldn't hold my hand on it but the bottom 2 seemed cooler. The telltale temp seemed warm enough to wash your hands with.Is this normal?
I gutted the tstat and the alarm went away but of course now i am afraid that it will be to cold. I did test the tstat and it did open at 140 deg. it just seems like the water will not flow until the tstat is open. The other reason I think this is I removed the waterflow sensor when it was running and then replaced it and the alarm went away. Almost like it has an airlock. where should I look or am I just thinking I have a problem?
The tell tale only indicates that the pump is working.
Sounds like you have a blocked water way or the thermostat is no good.
Try removing the lower unit and the thermostat and using a garden hose very intermittently shoot some water into the thermostat cavity to try to clear any blockage. It is common with outboards that a failed impeller can cause a blockage. Bits of the impeller get caught up in the system. There is no guaranty that this will clear the blockage but it is your best shot short of a tear down.
Replace the impeller anyway. They are not expensive.
I did replace the impeller and the telltale is still very warm. The engine doesn't overheat as I had it out for about an hour the other day. I was just surprised that the the telltale is so warm. Maybe someone who has one of these can tell me theirs is the same.
That alarm is not a "water flow" alarm. It is an "overheating" alarm. These are not the same conditions. The telltale merely indicates the water pump is working. An engine can still overheat even though the telltale shows a good stream. The fact that you can't hold your finger on the top cylinder is telling you the engine is indeed overheating. You need to put a new thermostat in, clean or replace the bypass valve, and then try it. The bypass valve opens at higher rpm so if it is defective, the engine would overheat at anything above about 2000 rpm or so. If the thermostat is stuck shut the engine would overheat at idle. If were stuck open it would likely not idle well but should not overheat. if the stat and bypass valve are ok, there are other issues.
Well I removed the lower unit again and flushed water from the tsat opening down through the tube and then back and then back down etc. I did not notice whether I had dislodged anything but I seemed to have good flow. I reinstalled the unit and noticed that one of the rubber grommets that fits on the water tube had a bit of a kink in it so it may not have been sealing well, I'm not sure. I put the thermostat together again and ran it on muffs. The telltale seemed to have the same pressure but I could definitely feel the water temp changing as the tsat opened and closed. The top cylinder was running still warmer than the botton two but I could hold my hand on it for a longer time. My guess is that I either dislodged something or I got a better seal on the water tube. I will know after this weekend how she runs.