1989 Mercury 150 Blackmax V6 trouble

shady8240 · Jun 16, 2003

First day in the water this year and I was cruising around with the family for a few hours. i was running about 4500 rpms on the way back to the marina and the engine got really loud. I immediately throttled it down to idle, and it cut out. I tried to start it back up, and it wouldn't even turn over. After five minutes or so, it started back up and it sounded like crap. If it were a car I would think that I threw a rod. Ran it for about an hour after the incident, limping back to the marina at about 1200 rpms and it sounded like crap the entire way back. I checked for flow from the pee hole on the ride back, and it looked normal. I did notice that the lower part of the engine, (down to the prop), was steaming. When i got to the dock, I put it in nuetral and it didn't seem to make the metallic clank that it was, and it revved up fine although it seemed to smoke a bit more. I am new to boating and don't know a damn thing about outboards. It is not oil injected and it did have a good mix in the gas tank. Am I screwed or is there an easy way to tell???? Thanks

nilsson · Jun 17, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

Hi Shady I own the 135hp version of your motor (same powerhead, different carbs) and realise these are complex units that need careful attention and checking. It sounds like you may have a blockage in one or more of your carbs causing a lean/hot mixture. Do you know the history of the motor?, how often was it run and how long did it sit idle before you bought it?. Gas goes stale after 2 months, causing blockages in carbs- not good!. When I bought my boat/motor, I took it straight to an expert to go right over it after seeing all those cylinders, carbs, wires etc- all very expensive!. Did you use TCW-3 OUTBOARD oil, or better still, the genuine Quicksilver blend?. Was the oil injection properly removed and did you mix the oil EXACTLY 50/1?. These older motors need the best oil at the correct ratio to keep 'em alive- honestly!. Also, people on here might disagree, but I prefer to use Premium gas in these big horse V6's. Better to have a few octanes to hand rather than risk blowing a powerhead from detonation caused by "Joeblow's Butcher and Outboard Wrench" mis-timing the ignition. I would remove the heads (very easy on these) and check for scoring and blown piston/s then go from there. It sounds like SOME damage may have been done, BUT my trusty Merc mechanic told me these motors can soldier on AFTER the cause is corrected. He told me that good fresh gas, maybe 40/1 ratio of oil (not normal 50/1) and gentle running for few inshore trips can sometimes reduce the scoring somewhat giving you 2-3yrs extra on your motor. Then again, if you venture offshore, you'll be looking at a reconditioning for safety- maybe just new pistons/rings and honing if youre lucky. Let me know how you go, I'm very interested in how people deal with this model of engine. good luck Nilsson

nilsson · Jun 17, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

Also shady... I know youre new to boating but.... did you or someone check the thermostats and pressure relief valve?. These motors have two thermostats, one on each head and a pressure valve mounted low on the starboard side of the block. All are CRUCIAL to correct engine temp (should be 140deg). I had all of these replaced, PLUS had new waterpump, oil injection removed and a full tune/adjustment service- I now trust this engine in offshore trips, no probs. Not blowing my trumpet but I believe ANY big horse V6 be given a BIG check over before the maiden run. Good luck nilsson

shady8240 · Jun 17, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

Thanks a million for the info. My 50:1 mix is on the money but the gas has been sitting in the boat for about six months or so. I keep it at a marina and I did have the boat last season. I don't know a whole lot about the boat prior to my ownership but the folks I got it from were decent people. I had it winterized last fall, I had the fuel/water seperator replaced, and I had a new water pump installed last season as well. Havn't checked the thermostats or anything under that black cover for that matter but my mechanic is looking at it soon. I'll let you know what comes of it and hopefully it isn't too bad. Thanks again, have a good day.

Moving Target · Jun 17, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

You say it rev's fine in neutral and makes no noise, but it did/does in gear, sounds like the power head is fine. I'd be looking at the lower unit, sound like thats what tore up.

nilsson · Jun 17, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

Hi Moving Target Your thoughts on the lower unit sound more than feasible except for the fact that Shady mentioned that after the "burn-up", he couldnt restart and had to wait 5 mins 'till cool down. When he finally could retart, it sounded like crap then had to crawl home at 1200rpm. So, either Shady's powerhead unseized or maybe, yeah, his lower unit freed up a little to allow the limp home. Either way, hope Shady has a happy outcome Nilsson

bigbluebirdy · Jun 18, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

Howdy, I have a 1985 Black Max 150hp... Two months after I bought it (three years ago) I had basically the same thing happen. Horrible noise while cruising along one day, and then was able to limp it home. Turned out to be the lower unit needed total rebuild. Gears and everything were all rusted out, from lack of use and care by former owner. $1400 later, it has run great for the past three years. Take care of it, and you can't ask for a better motor. I'm going to guess and say that your lower unit is gonzo... Let us know, and good luck.... bbb

shady8240 · Jun 18, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

Thanks again for the replies. This thing is driving me crazy cause I have a business and this is my peak season. Don't have a bit of time to start messing with the thing and I'm at the mercy of my mechanic at the marina and he is swamped. Does anyone have any suggestions on any little "tricks" to point me in the right direction. Is there any sort of simple tests that I could do to find out if it is the powerhead or the lower unit? Again, thanks for the info everyone and I'll keep an update of the turnout. Good day.

Outrage 19 · Jun 18, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

Do a compression test that should give you some idea if it's the engine or the lower unit

AndyL · Jun 18, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

I would suggest draining some oil out of the gearcase and inspecting it.The drainplug also has a magnetic pin that will attract debris. Obviously if the oil is full of metal filings and the drain plug has attracted larger lumps of metal fragments you can pretty safely be assured that the problem is in the lower unit. I hope not for your sake. Good luck. Andy

Moving Target · Jun 18, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

I would take AndyL's suggested course of action. If the lower unit lube is full of filings, it's gone. Although I think it would be cheaper to rebuild the lower unit than the power head.

shady8240 · Jun 23, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

Drained the oil and found the tell tale culprit, I think. Looks like the lower unit went through a dimanond tipped garbage disposal. Waiting for the estimate from my mech, but I'm looking at a 2003 175 hp Mercury. Trying to decide if I want to throw money into the old motor or if I want to have "no worries" if that's possible with a boat motor. Thanks again, Shady

AndyL · Jun 23, 2003

Re: 1989 Mercury 150 Blackmax V6 trouble

Sorry to hear the bad news. They say owning a boat is like standing in a shower and tearing up $100 bills. Andy

1989 Mercury 150 Blackmax V6 trouble

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