Thread: F100: Did I find something here?

Some of y'all may know I'm working on an F100 Yamaha engine that supposably locked up after overheating on it's previous owner. And that was a couple months after that previous owner had the engine rebuilt.

Anyway, I've replaced crankshaft bearings, and have had a difficult time getting it running. While doing so, I've run it briefly, and I've compression checked it, all while out of water. I didn't think it harmed the impellor, but I was wrong. I opened up the water pump and found this:



I took it apart, and was ready to install some new pump parts. And then I came across this (ignore the metal cup thing which I mangled removing it from the housing):



In the first pic, there is no gasket between the steel plate, and the impeller & it's housing.

In that second pic, that green gasket was found below the steel plate. I think that's wrong, that specific gasket belongs above the steel plate, and the housing.


The correct gasket for below the steel plate is pictured below (I already put it in it's place), and not the one I'm holding in my hand. When the one I'm holding in my hand is placed under the steel plate, I believe there's a gap then, which allows the impellor to suck air between it's chambers. Which makes for real poor pumping water action!!! Tell me I'm wrong?



Could this have added to this engine over heating on the previous owner.

Plus, when I did first start the motor after I put it together (when it was running poorly), I did run it in water, and I don't remember it peeing water out the pee hose. hmmm

I'd say you're correct. it looks like someone botched the previous install.

Told you about peeing!

You definitely found the problem. If the same guy who rebuilt the engine installed that water pump it kinda lines up with the rest of the story right. I'm very dyslexic so I lay the service manuals right next to where I'm assembling something or in a Outboard engine's case I use a computer outputting to a 24in monitor with Boats.net exploded diagrams pulled up. I match the part numbers before placing any part in place. No Guessing At All. The cost to replace a Powerhead to the possible monies made is too high a risk for me to even work anymore. Newer Boat owners do not have the common courtesies to know repairs do not happen fast, are not cheap, and are not warrantied against stupidity. Especially if they want perfection. My older customers knew, Rojo is not fast, he is not cheap, and he will close his shop if he thinks the Crappie are biting. They would pick up their boats and never return because I didn't fix something right. Today's Outboard Mechanics are parts changers not troublshooters.

Originally Posted by Rojo

You definitely found the problem. If the same guy who rebuilt the engine installed that water pump it kinda lines up with the rest of the story right. I'm very dyslexic so I lay the service manuals right next to where I'm assembling something or in a Outboard engine's case I use a computer outputting to a 24in monitor with Boats.net exploded diagrams pulled up. I match the part numbers before placing any part in place. No Guessing At All. The cost to replace a Powerhead to the possible monies made is too high a risk for me to even work anymore. Newer Boat owners do not have the common courtesies to know repairs do not happen fast, are not cheap, and are not warrantied against stupidity. Especially if they want perfection. My older customers knew, Rojo is not fast, he is not cheap, and he will close his shop if he thinks the Crappie are biting. They would pick up their boats and never return because I didn't fix something right. Today's Outboard Mechanics are parts changers not troublshooters.

I highlighted my favorite part.

And this is why I never trust anyone to fix my stuff. Except maybe Rojo.

I will try to fix it, learn from it, buy new parts, clean old ones, still don't work, start at step one. 100% of the time I come out ahead. Either by saving money, or by learning something I dint know, both ways, I'm a winner.

I’m buying Amazon stock immediately!

Wow. Ugly impeller. Glad it’s coming along nicely. Going to be fun

I was watching a Youtube video in which some youngsters had taken their dads big center console boat out. Boat was fairly new with a 250 Mercury hanging off the back. They loaded the boat on trailer, trimmed the motor up and pulled it half way up the ramp. The problem was the outboard was still idling out the water while they goof around. After about 3 minutes the motor blew a big puff of smoke and that was it . The guy shooting the video was in near tears because he knew that outboard cost 25k+. I found myself yelling at the video "turn off the freaking motor". I can only imagine how dad must have felt when the returned it.

Something along these lines might have happened with the previous owner ....

Originally Posted by CrappiePappy

Something along these lines might have happened with the previous owner ....

Sir CrappiePappy is pointing out something I will not touch on the V-6 Yamaha engines. One engine(I think it is the 225HP) is not a Interference Engine (Valves will hit the Pistons when out of time) the rest the Valve timing has to be perfect. All the points must be perfect the first time. I think the 4 cylinders like Slabs has a single tensioner but the V-6 engines you have to line up several marks before putting the belt on. Since the Cam Pulley is a Variable Valve Timing Pulley they can fail causing a Run-Out problem with the belt alignment shaving the belt at first but over time damage it like the picture Sir CrappiePappy provided. Moral of the story if you run a Yamaha V-6 remove the Cowl periodically, remove the large black plastic cover over the Flywheel, and look for black dust accumulating around the two Camshaft Pulleys. You want to catch that failure in the beginning stages. The timing belt will crawl downward too, it rubs on the block when the Pulleys begin to fail.