Mercury outboard 175hp Blackmax 1985 (overheating)

NESAR

Petty Officer 2nd Class
Joined
Aug 21, 2011
Messages
131
Hello, I have a few questions?

I just had my motor worked on and is overheating this is what was done. Thermostats (one on each cylinder head), poppet valve and impeller has all been done. The boat has no gauges hooked up at this time because we have not finished it yet. When we took it in a fresh water pond it overheated on me. The pee was strong and had a good stream. it ran good at first and moved well at max 3/4 throttle. If I have a strong stream coming out of the pee hole is water getting to the top of the block and is there a test I can do to make sure the water is flowing throughout the motor? Compression test is strong at 140+ per cylinder. Almost forgot I also did a full carb rebuild. When taken them apart all 6 jet screws were missing but replaced when rebuilt. The boat is a 20 foot v hull and has a 18 pitch 4 blade prop. Also the oil tank has been taken out and is mixed manually and was not mixed incorrectly. At trial the head was very hot and locked up when I tried to restart it. It will start now.
 

Dukedog

Captain
Joined
Oct 6, 2009
Messages
3,235
Re: Mercury outboard 175hp Blackmax 1985 (overheating)

If it was hot enough ta "lock up" ya might wanna pull tha heads ta look at tha holes no mater what thaa comp. gauge says. That's supposed ta be a chrome bore block. Jet screws? Hi-side jets and holders? What size jets installed?
 

NESAR

Petty Officer 2nd Class
Joined
Aug 21, 2011
Messages
131
Re: Mercury outboard 175hp Blackmax 1985 (overheating)

I'm not the mechanic, I'm just the owner. The jet screws we got were OEM parts from Merc part # 1399-3518 We buy the parts because we are tax exempt and get a lower rate then a dealer from Mercury. The mechanic told me that it was a big job and would be to much of a cost to pull it apart. We are a non profit with a very small budget. We have about 700 into the motor this year and have no money left to do this job. I can do some test but when it comes to ripping it apart i'm lost.
 

Dukedog

Captain
Joined
Oct 6, 2009
Messages
3,235
Re: Mercury outboard 175hp Blackmax 1985 (overheating)

I understand your deal now. But as your finding out there in nothing "cheap" with these motors. Even tha older ones. Pulling tha heads (not a very big "tear down" issue, 30 ta 45 min. complete reinstalled) and new head gaskets (if tha cylinders are ok) is probably one of tha cheapest and most beneficial checks that can be done after a severe overheat problem. If it was a little closer I wouldn't mind donating tha check out. Gl with it and hope for tha best for ya............Just maybe someone close will see this and be some help.......
 

NESAR

Petty Officer 2nd Class
Joined
Aug 21, 2011
Messages
131
Re: Mercury outboard 175hp Blackmax 1985 (overheating)

I was told it would be a grand or more for the repair plus parts. If there is someone who can help us out that would be great we are located in Cranston, RI. I'm pretty handy but never done the job and don't know what to take off. Do you think the ports are all clogged up? It is a salt water motor but every time we pull the boat out we flush it with fresh water except the last time when it broke down on us and were unable to flush it until it got back running. Is there something we can flush through to reopen the ports with out pulling it all apart?
 
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