Looking for advice- 65ESL72 issues

[GrizzleDizzle]

Well the motor ran pretty well the first 4 or 5 times I had it out, aside from some vibration at higher speeds that I suspected was related to the prop. Then I replaced the spark plugs and greased the prop shaft, and my next time on the lake it ran really bad. Heavy, boat shaking vibration at low speeds, and stalling. I’m guessing that’s the point where the impeller finally but the dust. Or maybe it was already in poor condition but functional up to that point but finally turned into a pile of pellets that day?

So since that day I’ve rebuilt the carbs and replaced the fuel pump, and today I’m installing a new thermostat and replacing the impeller. I also have a spark tester and compression tester now, so I’ll be checking those things as well. And the exhaust gaskets finally shipped as of yesterday, so I’ll install them as soon as I have them. My gut tells me this motor was well taken care of for most of its life but was stored away in someone’s garage for a number of years before I wound up with it, so I’m not shocked I’m running into gasket failures at this point.

On the positive side, I’m learning a ton about this motor and enjoying the troubleshooting process.

 

[GrizzleDizzle]

What I understood is that it runs okay for a bit, and then dies.


--DW

Well that was this issue initially...I really think I had multiple failures happen more or less at once. I know my fuel pump was leaking, so I replaced it and all of the fuel lines for good measure. Then I rebuilt the carbs. I had it running great on muffs and took it to the lake to fine tune the carb idle adjustments. It wouldn’t run for more than 15-20 seconds at the ramp, it would crank and fire up but stall out before it could even warm up. So I tied it up to the dock and messed with it a bit, adjusting the idle needles. Seemed to be running great, so I’d throw the cowl on and it dies within 10 seconds. Happened probably 10 times before I finally gave up and took it home.

I’m crossing my fingers that the only real damage done was to the exhaust gaskets...hoping the new impeller, thermostat and gaskets will get me thru fall without any more big issues. I’d like to be able to spend some money on restoring my boat for a change and stop playing whack-a mole with the motor lol

 

[webbd]

Just a quick thought after reading more of the replies to this post.

As mentioned in a previous post by an expert, a shredded impeller comes from turning the engine while dry, even for seconds. The engine might not overheat while running briefly without water, but it will likely overheat once on the water because the impeller is now destroyed. I made this mistake with my family's 5.0L MerCruiser many years ago and was admonished to never crank without water or plan on visiting the marine shop regularly.

I read an article a while back that showed a new impeller, a new impeller that had been run while dry for 10 seconds, and a new impeller that had been run while dry for 60 seconds. Imagine pressing down and dragging a pencil eraser across a dry piece of aluminum or steel for that amount of time. The new impeller was severely worn after seconds. It was shredded after a minute.

You don't ever want to rotate the engine without water. I accidentally kicked mine over without water once last summer and knew I had taken months off of the impeller's life.

-- DW

 

[GrizzleDizzle]

That’s good advice, Webbd. I definitely haven’t started the motor dry, but I’m guessing a previous owner must have. I do wish I would have replaced the impeller as soon as I bought it...rookie mistake I guess!

Eagerly awaiting delivery of my exhaust gaskets tomorrow!

I am curious, if anyone knows- what’s the most effective way to backflush an OMC motor? I’m going to be replacing the thermostat, can I run some water into the thermostat housing to flush out any pieces of the impeller that might be obstructing the cooling passages?