1993 Mercruiser 5.7, alpha one I/O..Temp rising

[Rick Fernandez]

Hello All,
Need some advice and help again please. Three months ago I had a temp rising at idle issue and I was advised by many here on the site to replace the impellar, which I did do myself and the boat's temp was great for awile after that, temp was reading 130-150max at all times. BUT, just recently our last time out on the water the boat was getting hot while driving, temp going over 175-185, wants to hit 200. Also while flushing with muffs, engine on, just doing a test, temp got hot again in only 4 minutes...I have a feeling something got lodged into impellar or the waterpump/thermostat, just not sure which one could be causing the problem?? Also, noticed something during flushes that I'm not sure about: Flushing with the muffs, water is exiting through certain holes of lower unit, and when flushing using the quick flush hose, the water exits only through two larger holes located near opposite sides L/R of the lower transom, but don't see it coming out of the same holes of when using the muffs....is that normal??? I never noticed this before...please advise!
I want to get out on the water tomorrow All your help is greatly appreciated! Rick

 

[tommays]

Re: 1993 Mercruiser 5.7, alpha one I/O..Temp rising

If the boat is on a trailer ?

you can only flush it with the muffs when the engine is running

useing a quick flush ? would not supply the water pump in the lower unit with water which would dammage it ASAP


tommays

 

[WAVENBYE2]

Re: 1993 Mercruiser 5.7, alpha one I/O..Temp rising

Ya I agree, if you were only feeding water to the engine with the hose and not the Alpha 1 you "might" have burned up the Alpha impeller again, how long did you run the engine with out an muffs on, anything longer than 10sec. could result in impeller damage.

 

[Rick Fernandez]

Re: 1993 Mercruiser 5.7, alpha one I/O..Temp rising

I hear ya, thanks for replying! We have it on a trailer when flushing, and when using the quick flush, we never have the engine running, and when we use the muffs to flush we have the engine running... We really only use the quick flush/engine off when we get in too late and don't want to bother neighbors with engine noise, and when doing this we flush it for about 10 minutes. Please advise! what should I check? thanks again!

Rick

 

[Don S]

Re: 1993 Mercruiser 5.7, alpha one I/O..Temp rising

The first thing you check on any overheat problem on a boat is the impeller. Too many things can cause them to go bad. A plastic bag or other "Debris" over the intake is a common problem.
When was the last time you had the impeller replaced? Those are a maintenance item you know. They only last for a few years, you have an Alpha I Gen II which will usually last 3-5 years, but not always.

 

[Rick Fernandez]

Re: 1993 Mercruiser 5.7, alpha one I/O..Temp rising

hey Don! thanks for replying as well, three months ago you were the one that guided me through replacing my last impellar with advice and manuals, it went well too! its been running like a champ since then with good temp readings. Now I have this new issue, I did run into some mud previously but I didn't get stuck, however maybe it did suck some muck into the impellar and screwed it up. I guess I'll be taking that baby apart again!!! Are you ruling out the thermostat or it might be that as well if the impellar looks ok???

 

[tommays]

Re: 1993 Mercruiser 5.7, alpha one I/O..Temp rising

If you sucked up muck i would look at the stat

It can act like a filter during my dredging attempts i have found many good size stones in the stat


Tommays

 

[Rick Fernandez]

Re: 1993 Mercruiser 5.7, alpha one I/O..Temp rising

Thanks! I will check the stat as well, run a test on it in boiling water, correct?? or do you suggest an other way? Or if it visible that something is lodged into it, then probably is the cause and don't need to run a temp test...correct?

 

[Rick Fernandez]

Re: 1993 Mercruiser 5.7, alpha one I/O..Temp rising

Do you have any charts for the thermostat R&R, that would help in case I can't find it in the manual. Thanks!

 

[Don S]

Re: 1993 Mercruiser 5.7, alpha one I/O..Temp rising

You have a possibility of 3 different designs used in those years. Your best bet would be to find a Mercruiser SN on your engine (Tag is on back of block just over the starter) so you get the proper OEM service manual if you don't have one. You are right on the changeover year. It's very common to have a 93 boat with a 92 engine package, or even a 2007 boat with a 2006 engine package. Engines and hulls don't start their new year at the same time.

 

[Rick Fernandez]

Re: 1993 Mercruiser 5.7, alpha one I/O..Temp rising

Thanks guys, I'm leaving now to start the surgery on the boat. I'll check the manual for the thermostat deal, hopefully it's just a small rock lodge in there and I don't have to mess with the impellar. I'll let you all know what it was. Thanks again for all your tips.
Rick