MerCruiser 8.1 HO - first long trip, want to reduce "mechanicals" anxiety

It's pretty easy... 3 screws and pull up on the filter housing. Replace filter in housing. Then use a pair of needle nose pliers and reach down into the module and pull the circular screen out. There is a 'tit' or nub right in the center to grab. Pull screen and replace. Then slide filter housing back in and tighten the screws. Start with the starboard first to get a feel because access is usually better than the port. The port side you end up usually having to pull the small screen blind.
 
Awesome! I’ve been ordering parts all week, so I’ll add these to the list. I’ve ordered a service manual, but it’s not due until sometime next week.

did I screw anything up by opening that blue valve on the cool fuel unit?
 
jmauld said:
Thank you for the link. I ordered two sets, but was just curious. What’s the difference between these and the plethora of 8.1L wire sets on summit racing?
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Fitment, i.e. length, angled boots and fittings that hold the wires to the manifolds. That is, they are specifically made for the marine 8.1.
 
jmauld said:
Awesome! I’ve been ordering parts all week, so I’ll add these to the list. I’ve ordered a service manual, but it’s not due until sometime next week.

did I screw anything up by opening that blue valve on the cool fuel unit?
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Nope. It just drained the cooling water. It will refill when the boat starts.
 
Why would the coolant water be really stinky black water after I just ran it? Does this part not get a lot of water flow?
 
jmauld said:
Why would the coolant water be really stinky black water after I just ran it? Does this part not get a lot of water flow?
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It should, however, they have redesigned it several times due to inherent flaws. Take off the end hoses and make sure the hose and cooler ports are clear. They can get clogged. Should look like this...

Edit - see the black nut on the rear? Remove that. Hoses pull out.

20210328_141519.jpg
 
Completed sea trial/survey on the Wellcraft. Surveyors first impression was "nice boat for the age".

He could not find moisture anywhere, not even on the swim platform. A few small things like the sump pump was not working (been there done that), trim tabs did not work (looked low on fluid), few cabin light bulbs were out. etc.

Genny fired up and ran nice. It popped a few times when adding load, but did not shut down and would settle back down quickly. It did handle a full load the, up to 20. Not sure what the popping was about, sounded like a backfire almost.

When trying to get up on plane the starboard motor popped, and shut down. We could not get it restarted. Seller remembered that's the motor/fuel tank he accidentally almost ran empty recently because he did not understand the fuel gauges. He told me this when I first looked at the boat, it was listing pretty bad then. He put 220 gallons of fuel in that tank last week and the listing went away.

Back at the dock we pulled the fuel water separator. Not good, lots of brown and water. We turned the starboard fuel gauge off, switched to port, purge the fuel using a fuel pressure gauge to pull clean fuel thru to the rail from the port tank. Got clean fuel, replaced the fuel water separator and tried for a while but the engine still would not start.

Seller is going to talk to the marina mechanic. I suggested he pull the plugs to blow any water from the fuel out and have the injectors cleaned. I also think that fuel tank needs to be pumped out and cleaned.

Surveyor only charged me 1/2 price, even though he was on the boat for almost 5 hours trying to help diagnose as well.

Oil Reports came in as well:

Port engine:

GREG: Fuel dilution at 5.5% is enough contamination to indicate a fuel system issue, especially if the oil
level is rising. Sodium may be harmless oil additive, but without knowing what brand this is we can't say that
for certain. We left it marked, since sodium can potentially show contamination by seawater. Iron shows
heavy wear at steel parts like the cylinders and shafts, which may be related to the contamination. Tin is
typically a bronze alloy. No significant dirt or excess solids were present. For reference, Mercruiser 8.1L
universal averages are based on oil run for about 60 hours.

Starboard engine:

GREG: 4.0% fuel is less than what was in the port engine's sample, but this much is also high enough to
potentially show an issue. As in the port engine’s sample, sodium may show seawater contamination, but it
may also be harmless additive in this brand of oil. Note that iron is lower over on this side, which is
noteworthy since we typically expect twin engines to look similar in testing, and when they don't it can reveal
an issue in one of them. Elevated tin alone isn't usually concerning since it's typically an alloy in bronze.
 
Shop pulled the plugs, fogged the cylinders, turned the engine over, installed new plugs, engine started right up. Next their going to clean the fuel tank.

I hate to say this, but the whole thing has left a bad taste in my mouth. No reason it should really.
 
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mrsrobinson said:
Shop pulled the plugs, fogged the cylinders, turned the engine over, installed new plugs, engine started right up. Next their going to clean the fuel tank.

I hate to say this, but the whole thing has left a bad taste in my mouth. No reason it should really.
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For those following along at home, I decided to pass on this boat. Just didn't feel right after the sea trial (attempted but failed) and survey.
 
If you do not know the condition of the batteries get a jump start booster. You probably will not need it but if you do you will have it. It will have enough power to start your generator to charge the main batteries if you have a problem. When we got our present boat we went out with little battery knowledge and found our two start batteries did not have enough power to start the engines. Generator was on separate battery and it started. Took half an hour to charge main batteries to get engine going. I replaced all batteries after that.
 
northern said:
If you do not know the condition of the batteries get a jump start booster. You probably will not need it but if you do you will have it. It will have enough power to start your generator to charge the main batteries if you have a problem. When we got our present boat we went out with little battery knowledge and found our two start batteries did not have enough power to start the engines. Generator was on separate battery and it started. Took half an hour to charge main batteries to get engine going. I replaced all batteries after that.
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That's good feedback. This happened to me before, luckily like you the generator started and I was able to run the battery charger for a while and then replaced both engine batteries.
 
mrsrobinson said:
That's good feedback. This happened to me before, luckily like you the generator started and I was able to run the battery charger for a while and then replaced both engine batteries.
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After all this time, what boat was this? I was perusing FB marketplace other day, there a lot boats for sale in MD & VA. Take a look.
 
2002 Wellcraft Martinique 3700 in Hopewell,.VA.

I found a nice private seller Cruisers Yachts 320 yesterday close to Baltimore, MD, about 3 hours from my house. Talked to the seller, did FaceTime to see the boat, then made a full price offer contingent on sea trail and survey. 2 hours later he called to tell me he got a full price offer from somebody in Chicago with no contingencies. Boat was on the market for a couple of days.
 
mrsrobinson said:
For those following along at home, I decided to pass on this boat. Just didn't feel right after the sea trial (attempted but failed) and survey.
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I think your instincts on that one are right. When I hear owners giving explanations like you got, alarms go off like a slot machine in Vegas. Then when you get weird test results and a failed sea trial, its time to walk away.
 
Something to me just doesn't add up.

If the fuel dilution is 4-5%, that means that with a 8.1L sump of roughly ~9 quarts, roughly ~1/2 quart in your pan is fuel?

And if that's true, why would that happen to both engines? Highly unlikely unless the engines have been idling around the entire season or an injector is stuck open (possible but still not adding up to me). Fuel dilution on injected engines can happen, but much less likely vs. a carb engine.

If the bilges are clean and they match the condition of the rest of the boat, it sounds like all signs point to a boat that maybe just hasn't been run with frequent use. So you throw a set of injectors in each engine and you clean the tanks. Problem solved. In my opinion, these aren't show stoppers, but to each their own.

I wish I could get my hands on it to do my own assessment.
 
mrsrobinson said:
2002 Wellcraft Martinique 3700 in Hopewell,.VA.

I found a nice private seller Cruisers Yachts 320 yesterday close to Baltimore, MD, about 3 hours from my house. Talked to the seller, did FaceTime to see the boat, then made a full price offer contingent on sea trail and survey. 2 hours later he called to tell me he got a full price offer from somebody in Chicago with no contingencies. Boat was on the market for a couple of days.
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Same thing happened to me. Was looking at a nice Tiara and had a question about the transmissions -- one blue, one black. While the broker was getting the answer, they go a full price offer, sight unseen.

Second one was a new buyer, who bot a 33 sundancer out from under me -- didn't want a survey.

Buyers are stupid these days -- have more money than brains.
 
douglee25 said:
Something to me just doesn't add up.

If the fuel dilution is 4-5%, that means that with a 8.1L sump of roughly ~9 quarts, roughly ~1/2 quart in your pan is fuel?

And if that's true, why would that happen to both engines? Highly unlikely unless the engines have been idling around the entire season or an injector is stuck open (possible but still not adding up to me). Fuel dilution on injected engines can happen, but much less likely vs. a carb engine.

If the bilges are clean and they match the condition of the rest of the boat, it sounds like all signs point to a boat that maybe just hasn't been run with frequent use. So you throw a set of injectors in each engine and you clean the tanks. Problem solved. In my opinion, these aren't show stoppers, but to each their own.

I wish I could get my hands on it to do my own assessment.
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Yeah, at a fair price I probably would have moved forward. He would not budge off the agreed price after learning this about the motors though. Bilges were not clean either, not a mess, but not clean. Oil level on dipsticks was high on both engines, suggesting fuel IMHO since they were both just changed 10 hours ago. Unless his mechanic added too much oil. Seller reported 12 hours of use in just under 2 years.
 
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