Lost compression in two cylinders on a 600 hr engine

[MDRichmond]

Hello all,

First post from a new owner.
I bought a 1995 Ski Nautique a little over 10 weeks ago and its run well each week end other than some initial speed reductions that we thought was an old fuel problem and was corrected with a couple of bottles of sea foam. 5.8 HO PCM Pross Boss GT 40 engine has 600 hours on the counter. This past weekend we lost significant power on the ride home a had significantly more engine noise than normal.

I just heard back form the dealer today that we've lost compression in two cylinders and that a prong of one of the spark plugs is missing (presumably having fallen into the engine somehow.) They've told me a new engine is the only option.

Questions:
Is this really the only option or is there any hope of repair?

The previous owner had told me that he had recently replaced the plugs and plug wires. Is there any hope of pursuing the plug manufacturer over a faulty plug or is that a waste of time?

Any other thoughts or helpful advice?

[bturner]

With a 95 and 600 hours unless you're an engine builder kind of person the dealer is probably giving you sound advise. You could tear down the engine or at least pull the heads and inspect the cylinders in question but if you had a piece of metal go through a cylinder your probably going to need more than a band aid to fix it. Seeing two cylinders fail typically indicates that there was something more going on like either an oiling or cooling issue which could have led to the spark plug issue as well.

Losing a tip on a plug is pretty rare these daysand I really can't say that I've heard of that happening since the days of spark knock when manufactures were switching fuels and messing with the timing to get cleaner emission numbers or when some my friends were experimenting with Nitrous. You can always try but I doubt any plug manufacture is going to give you anything other than maybe a new set of plugs. There's also a real good chance the tune up came in response to an underlying issue which the PO thought the tune up would fix.

Unfortunately a long block would appear to be in your future. The good news is that on your boat this is something that you might be able to tackle yourself with moderate skills and YouTube...... Of the boats to pull an engine in the straight inboard is probably the easiest. You can find remanufactured and new engines at decent prices especially at this time of year. The place most people use up here is Michigan Motorz.....

https://www.michiganmotorz.com/marine-engines-c-31.html

Good luck with your boat.

[scottb7]

I would replace all the plugs and see how it drives...That is what I would personally do. Do you now the compression numbers? Maybe the loss of power you experienced is from the loss of the missing prong, and other that that the power is sufficient for your needs. And certainly with a fixed plug your gonna have more power, cause that cylinder wasn't firing...

[MDRichmond]

Thanks for responding bturner and scottb7! I don't know the compression numbers but we went from easily doing 35-40 mph to 11mph....I'll ask the mechanic and see what he says. I need a lot of power to pull my 220 lb self out of the water on a slalom ski though....

If I'm going to have to get a new engine, do I have any options? Is there a engine that would be better or more reliable than some other one? Or is there only one option that fits this boat? If I need to spend a bit more money replacing a few other parts to make a more reliable engine work, I'm willing to look into it.

[Nautiquehunter]

Get a second opinion from a real engine mechanic. What two cyl's went bad are they next to each other. Of course replacing the entire engine will fix the problem . Why not just fix the problem with the engine and go from there . 600 hours is nothing in that engine.

[bturner]

The season's pretty much over and a second opinion is always a good idea especially if there is another shop that you know does great work or specializes in engine work that you can take it to.

I would also agree that 600 hours are fairly low for that engine. My concern or decision point would be..... how much do you spend on a repair versus getting a new engine? That's going depend on what's actually wrong with it and what would need to be done to repair it. If for example the engine has to come out for the repair the labor is going to be the same or very close to the same for the repair as for the replacement. So that's a wash. Depending on what they find (if it's internal there's going to be cost for parts, machining and labor to do the repair) the cost to repair could be close to or more as replacing the engine when all costs are figured in. A new long block is $2400 so the delta between that and the repair is really what you're looking at while also keeping in mind that on the new engine everything is well, new. Depending what's done during the repair process only the parts being repaired on the old engine would be new.

That said it's very possible that you've only blown a head gasket or something more minor than having destroyed a cylinder or two and that this shop is not interested or not capable of diagnosing the engine failure past a replacement. If that's the case you could save thousands with a second opinion and better shop or at least one that is willing to dig deeper into the failure.

[functionoverfashion]

Get a second opinion from a real engine mechanic. What two cyl's went bad are they next to each other. Of course replacing the entire engine will fix the problem . Why not just fix the problem with the engine and go from there . 600 hours is nothing in that engine.

Definitely get a second opinion. If you lost compression in two cylinders and they're next to each other then it starts to look a lot like a head gasket failure. If a piece of a spark plug went into a cylinder, it probably did some damage, but maybe not so much as to scrap the whole engine.

Either way, we (you) need more information on what diagnostic steps have been taken, and with something like this, you should definitely get a second opinion.

If it were my boat, I'd pull off the head on the side where the plug failed, and see what that cylinder looks like. And the head gasket.

[MDRichmond]

Thanks all, I've emailed these questions to the current shop but they're closed on Monday's. I'm going to get a lot more information before moving forward and unless something catastrophic becomes very clear, I'll also get a second opinion. The rough estimate (at 4:45 on a Friday) for the new engine swap was $7500. Does this sound reasonable if that is what needs to happen? bturner where are you getting a long block for $2400? (obviously doesn't include labor but curious to shop this to if needed.)

[bturner]

Sorry, I just checked again and it's re-manufactured, apparently all the fords they have are but it's still $2500.

https://www.michiganmotorz.com/ford-...ed-p-3539.html

GT 40 heads are another $600 if you're feeling sporty.

Around here engine replacements are going for about $6K all in so $7.5K would seem high. I would differently shop them or if you're not going to make this an adventure and try it yourself.

[MDRichmond]

Email back from the dealer below....time to look for a new shop....

The compression on this engine should be 130-215 PSI. The compression on this engine is 100, 0, 0, 150, 145, 140, 160 and 145. There are several reasons what could have caused the 0 compression. Freeze damage, over heat, broke valve spring, head gasket. We have no way of knowing what caused it unless we tare it down and inspect. Most common cause of the spark plug damage is caused by water intrusion. The quickest way to get you back on the water is to replace the engine. We do not rebuild engines. I hope I answered your questions. Please let me know if you have any more questions.

Cylinders 2&3 are the problems children and are right next to each other...

[bturner]

100 is not good either. Rule of thumb is 10% between cylinders.

Agree though with finding a different shop. The valve spring could be quickly checked by simply removing the valve covers and the head gasket by removing the head on the side with the issue. They obviously don't want this type of business and you're better off going somewhere with a deeper skill set either direction you decide to go.

Did you notice an overheat problem when you had it out? If so you'll need to figure that out to if you decide to rebuild.

[gun-driver]

A loose plug can also cause detonation and the result you mentioned. What motor is in the boat is it a GT-40?
I agree with finding a new shop, you'll never see 200 PSI on a stock motor

[MDRichmond]

I did not notice any type of over heating.

Yes it is a GT 40.

Some new info: I picked the boat up from the shop today and got some more info (I think the service manager is just really bad at communicating the full scope of the situation)
Apparently there was a lot of water coming out of the engine when they pulled the plugs and it appears that one of the exhaust manifolds has previously been replaced. The service manager is convinced that there is pervious freeze damage and that the water in the cylinders would indicate a crack in the block or the exhaust manifold. It's starting to make more sense as to why he is recommending a replacement but I'm still not sure. I need to find someone who can look at it and clearly explain what is going on.....My car mechanic is checking with his contacts to try to find me a good boat mechanic at this point......

[Peter6000]

I would do a leak down test. You can easily do it yourself. All you need is a tester you can get one at harbour freight for around $50 and a compressor.
What it does is pumping air into the cylinder an measures the air flow.
Now you can listen to it and hear where the air comes out.
For example if you hear it in the exhaust you have ehaust valve problem
If you hear it in the intake your intake valve is the problem, if you hear it in the oil chamber the problem is your piston or rings.
This will tell you if you need a new engine or just a head repair.
Further I had my engine and heads rebuild some 6 years ago if I remember right it was around $1600. I shipped it to a place in Miami. Has been running great since.
If you interested I can dig out the invoice an send you the details.

Sent from my SAMSUNG-SM-G870A using Tapatalk

[MDRichmond]

Update: At a new mechanic and I've got a blown head gasket and a cracked head on one side....We're looking for a new head and they're apparently difficult to find. Anybody know of someone selling a GT-40 head that would fit a 1995 PCM 5.8 HO ford block?