3.8 Mercruiser overheating for the first time

[kdrags68]

Hello all. 3.8 mercruiser with an alpha 1 drive. Had the impeller replaced at the beginning of the summer. Went out with it 5 times. No problems, except the carb had a big flat spot in it. I had the carb redone and completely gone though by a pro carb builder and had it set up for my area and altitude. I put the carb back on and started it for a couple of minutes to make sure it would start. Took it to the lake the next day and launched it. Got about 1/4 mile away from the boat dock and was in the red for temp. Shut it down and spent the next 3 hours trying to get back to the boat dock. I took the hoses loose on the water and there was no water in the block. I was dumping water into the open hoses with a can. I started it a few times and the water pump on the motor was circulating water. It just seems there is no water coming in from the lake. Can putting a new carb on cause this? The boat has never over heated before. The only thing can think of is the 2 minutes that I ran the boat with the new carb damaged the impeller. Can 2 minutes do that running dry? If that is the general consensus then can you point me to a link to change the impeller? (I had it done by someone last time and did not do it myself) I have searched the sight but haven?t found the link yet. Thanks.

 

[BeaufortTJustice]

Re: 3.8 Mercruiser overheating for the first time

If you ran it for two minutes out of water (without ears or anything) then yes, you probably ruined the impeller. Running it for even 5-10 seconds can ruin it sometimes. Sorry, probably not the news you were hoping for.

I am not familiar with your motor / outdrive, but someone else should be able to point you to information on how to change.

 

[Bondo]

Re: 3.8 Mercruiser overheating for the first time

I have searched the sight but haven?t found the link yet.

Ayuh,... At the top of this forum is the Adults Only section,..
In there you'll find links to the Alpha 1 Service Manual,...
It's all explained there...

 

[SSV177]

Re: 3.8 Mercruiser overheating for the first time

Oh yeah,two minutes is certain to burn it up.....i did the same thing years ago for about 10 seconds and smoked the impeller..water is the lube and is vital.

 

[cr2k]

Re: 3.8 Mercruiser overheating for the first time

Well now you know...NEVER start the engine out of the water with out muffs on it. You are running a rubber impeller in a stainless steel cage with nothing but friction. You most likely destroyed your housing too from the heat.

 

[longstand]

Re: 3.8 Mercruiser overheating for the first time

Dont worry man.. Replace the water pump is easy on the outdrive. damm book make it look so hard..

i have a twin engine i have replace both my impeller in about 1 day. the first time...

well i cheated really. its not recommedid.. also ihave a stringer. not Alpa..

So i guest it will be alot easyer for you.. but if you have stringer. just remove the bolts on the exhaust housing and let it hang.. but make sure to support the whole lower unit so it will not hang just on the Cable. or that will brake... i use a wood on the buttom on the lower unit so it hold its place not on the cable. and i just use a impact gun t remove all the Bolts.... Removing the Impeller housing was really the hardest part because its Stuck most of the time.....

but ye me.. thats how i change my..

Make sure you Seal that up and let it dry before TESTING it.. i let my Set for about 2 Days. just to make sure..

 

[ian79ian]

Re: 3.8 Mercruiser overheating for the first time

hi all im very new to this and an still trying to work it all out but i have a problem with a mercury blueband 500 50 hp i can get it to run but only with the bottom 3 spark plugs in every time i put in the top one it just wont start up its doing my head in as i cant work out what it may be any help would be great thanks

 

[ziggy]

Re: 3.8 Mercruiser overheating for the first time

kdrags, read this,

http://www.boatfix.com/merc/Bullet/87/87_14.pdf

if ya overheated, ya got yer work cut out for yerself.
ya need to get all the old impeller pieces out of the water system. they'll flow up stream towards the tstat. when i had to go get the pieces, i removed the lower and then removed the hose that feeds the engine the raw water from the lake.. then flushed both directions w/water into a bucket. caught all the pieces and many came out. i removed the tstat and found pieces there. i melted the exhaust shutter (flappers). ya can also melt the waterpocket cover, which you don't want to take off since the bolts that hold it on will likely break off. in my case, the seal had been damaged, so it had to go. i only broke three off of it. hopefully you won't have a leak there. maybe replace the waterpump housing.
i think there may be other problems needing to be addressed too.
you just got your first lesson in boat engines. sorry. i'll only speak for myself. but, been there, done that..

 

[Bart Sr.]

Re: 3.8 Mercruiser overheating for the first time

hi all im very new to this and an still trying to work it all out but i have a problem with a mercury blueband 500 50 hp i can get it to run but only with the bottom 3 spark plugs in every time i put in the top one it just wont start up its doing my head in as i cant work out what it may be any help would be great thanks

You really need to post this in the Mercury Outboard Forum.It is considered hijacking to post different questions in an existing thread.

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