Mercruiser/Alpha Water Circulation issues, Not the Impeller

Hello,

I have a recently rebuilt 383 stroker mated with a 1986 gen 1 alpha drive - same block as the original 5.7 from the same year. It was running fine when I winterized it last season, but I started it up for the first time last week and realized that no water was flowing through the engine. I didn't see anything coming out the exhaust and there wasn't anything being pumped in from the muffs. I instantly thought that the impeller was gone and went to replace it today, but it was 100% intact, as were all the other parts of the water pump. I replaced them anyways, as I was going to do it for standard maintenance, but now I am wondering what else could be stopping the water flow. After running the motor, I took one of the drain screws out of the block, and no water came out. Any guesses where to start? I did remove the drive for the winter. It seems like there is no water getting to the engine at all. Maybe the drive needs to come back off and check for something inside a hose? Any suggestions that could be done before pulling the drive would be appreciated.

Re: Mercruiser/Alpha Water Circulation issues, Not the Impeller

Find the hose on the thermostat housing that comes from the outdrive and remove it. Start the engine and see if anything come out of the hose.

Re: Mercruiser/Alpha Water Circulation issues, Not the Impeller

Don S said:

Find the hose on the thermostat housing that comes from the outdrive and remove it. Start the engine and see if anything come out of the hose.

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Thanks Don for the quick reply. Now if only the local Merc dealer hadn't given me the wrong water pump kit.... I guess troubleshooting is going to have to wait until tomorrow until I can get everything back together.

Re: Mercruiser/Alpha Water Circulation issues, Not the Impeller

There is only one kit that will even come close to fitting.

Re: Mercruiser/Alpha Water Circulation issues, Not the Impeller

OK...I got a bit lost here.... You said "I replaced them anyways" (referring to the water pump parts)...then in a subsequent post you said "dealer (gave) me the wrong water pump kit" and you need to get everything back together....

Is the drive still on the boat? If not, you can put a hose into the bell housing water port and run the engine that way to troubleshoot.... That is, if I am reading this correctly....

Re: Mercruiser/Alpha Water Circulation issues, Not the Impeller

greg82255 said:

Hello,

I have a recently rebuilt 383 stroker mated with a 1986 gen 1 alpha drive - same block as the original 5.7 from the same year. It was running fine when I winterized it last season, but I started it up for the first time last week and realized that no water was flowing through the engine. I didn't see anything coming out the exhaust and there wasn't anything being pumped in from the muffs. I instantly thought that the impeller was gone and went to replace it today, but it was 100% intact, as were all the other parts of the water pump. I replaced them anyways, as I was going to do it for standard maintenance, but now I am wondering what else could be stopping the water flow. After running the motor, I took one of the drain screws out of the block, and no water came out. Any guesses where to start? I did remove the drive for the winter. It seems like there is no water getting to the engine at all. Maybe the drive needs to come back off and check for something inside a hose? Any suggestions that could be done before pulling the drive would be appreciated.

Click to expand...

The impeller can be intact and still cause an overheat. I replaced mine (3 years old w/1 year of use, sat for 2... had a baby) this season, running warm on muffs with anything over idle. Would idle cool all day. New impeller kit, and good as new.

Re: Mercruiser/Alpha Water Circulation issues, Not the Impeller

If, when you put the upper and lower together, you missed the tube into the top of the pump, you won't get water to the engine. No matter how good the impeller is.

Re: Mercruiser/Alpha Water Circulation issues, Not the Impeller

I misspoke earlier, my apologies. My plan was to replace the water pump anyway. I haven't replaced it yet. I ran the motor with the water pump from last year still in there, the tube was in there too, and this is when the problem occurred. It worked all last year as it was set up. The only thing that changed was that I removed the drive for the winter and put it back on last week week.

As for the new pump not fitting, there is what looks like a small alignment pin (maybe 1/8" tall) on the lower unit that is supposed to fit into the rear left side of the water pump base. I'll see if I can get a picture up. The gasket didn't fit and there was no hole drilled in the new base for the pin. The base that I had in there had a hole in the gasket for the pin and a hole drilled.

Re: Mercruiser/Alpha Water Circulation issues, Not the Impeller

If you are still having problems I would put a tub under outdrive to see what comes out and put a hose in water hose in boat and and flush inside out to see if you have mud in line(s). That is how my problem got solved.