I bought a 2001 Yamaha 5hp 2stroke from a member here that had sat for several years. When I got it, I did basic maintenance (plug, rebuilt the carb and fuel pump, cleaned internal tank, fuel lines, water pump). Got it running like a champ, but it doesn't seem to be spitting water like I think it should. I know the water pump is attached to the water line, as it took me about 2 hours to get the water pump, shift linkage, and driveshaft to all seat. At idle, it seems to just spit a little water, not as stream. I have been told that I need to let it warm up and open the thermostat, which I did (ran for about 15 minutes, no change). I've also been told that this is normal operation for a Yamaha, as the telltale isn't under direct pressure and if it's spitting water it's working. I am concerned that something is amiss, as there seems to be exhaust spitting out the hole with the water, and its pushing bubbles from the side plug where you access the shift linkage, and through the top of the hole were the shift rod comes up through the lower unit. I am running the motor in a 5 gallon bucket full of water, and I am wondering if the exhaust is causing the water pump to suck the exhaust and cavitate the pump. Any thoughts before I tear the foot back off of it?

My 115 blows water out the “pee hole” hard enough that it shoots a stream 3” deep in the lake.

I’d remove the thermostat and take a look see. One of my thermostats was stuck partially open. I replaced them both.

That’s what I am thinking. I was searching the web today and apparently these motors are really popular in Great Britain on sailboats and rubber boats. One guy said he had to take the head off about every three years to clean the coolant passages. I’m pretty sure that was salt water though. This motor was actually really clean. Very well taken care of. I’m gonna fix a small fuel leak this evening then run it in a big cattle tub to eliminate my cavitation theory. Another issue is the lack of an easily accessible service manual. The only one I found was a download for like 40 bucks. Awful steep but so are the parts for these damn things. Guess I’m gonna Have to bite the bullet. Great little motor.

Talk to Hevi, he is a yammy guru. A factory tech.

You won't need a service manual to change the thermostat. Just be sure to order a gasket when you get a T-stat. Cheap thing to try.

There’s a few pieces of missing hardware and rubber I need to replace, so I’ll add a Thermostat and gasket to the bag. Guess I’ll order a head gasket if they’re not astronomical in case I need to pull the head. Gonna take the motor to the heated shop tomorrow night to work on. That wind was cutting this evening.

Stupid suggestion, but have you run a piece of weedeater line back up the pee hole? We get shell bottom on the east coast of FL that will clog that sucker up in a second. Think of it as a catheter

Are you sure you installed the key between the impeller and shaft? I’m sure you did, but I fixed one once, with similar issues, that the owner didn’t put it in.

I second the weed eater line trick also.

You don't have to remove heads to clean passages, you can boil them out with muriatic acid