On my third mechanic...

[RebelCobalt]

So the saga continues on my '98 VP 5.0Gi. As a reminder, this is the one with no compression in cylinder 1, allegedly due to it having too-short spark plugs. My first mechanic told me I needed to buy a new long block...

I'm on my third mechanic now, and he has got my boat running. He hasn't run a leakdown test yet, but he cleaned out the throttle body (full of fan belt dust), put new (and proper length) spark plugs in (the current ones were old and rusty, and one had blown the electrode), and changed my distributor cap (the old one was full of corrosion), and apparently it now runs OK.

Compression in cylinder #1 is lower than the others (50 compared with nearly 100), but that's better than when he started, and better than what the other two mechanics told me (close to 0). So he ISN'T recommending a new engine block, like the first guy, thank god...

So my new mechanic has recommended I just run the boat for a while and check-in in 12 months' time to make sure the compression is OK (he seems to think it will get better as I run the engine).

My questions are - will running it (when I know the compression is low) do any harm to the engine? Is it still worth getting a leakdown test?

 

[Gary H NC]

Re: On my third mechanic...

A leak down test should be one of the first things to be done.
I doubt the compression will magically get better.
Have they put some oil in that cylinder and then checked compression?

 

[scoflaw]

Re: On my third mechanic...

I bought a boat 2 years ago with similar issue. It had a manifold, riser failure prior to winter storage. The more I ran it, the better it got. Not sure if the rings were stuck or corrosion on the valves, but it runs smooth as silk now, by doing nothing. Marina I bought it from said to add a quart of Marvel MO to every tankful, 70 gal tank. Worked for me.

 

[Fishermark]

Re: On my third mechanic...

will running it (when I know the compression is low) do any harm to the engine?

No more harm than already exists.

Is it still worth getting a leakdown test?

The only point of doing a test is to find out what's wrong. If the engine runs now and you want to run it till it dies, then there is no need for the test.

If it were mine, I would want to know what the problem is and fix it. But that will involve some engine work one way or another.

 

[fossill]

Re: On my third mechanic...

Be it mine, throw in a quart of Rislone and run it long and hard for a few days. Then check it again. I doubt it will help, but you may get lucky for only a few bucks. Plus you got nothing to lose as if it don't help, you're putting in a new (or rebuilt) engine in anyways.

 

[bruceb58]

Re: On my third mechanic...

Using Rislone, Marvel MO, Sea Foam or any other snake oil will not fix or help his problem.

 

[scoflaw]

Re: On my third mechanic...

Using Rislone, Marvel MO, Sea Foam or any other snake oil will not fix or help his problem.

Worked for me,bud. I say run it.

 

[bruceb58]

Re: On my third mechanic...

Worked for me,bud. I say run it.

Amazing what people beleive.

 

[LAC_STS]

Re: On my third mechanic...

Why don't ou go get a leak down tester and/or compression tester and check it yourself?

You can get one pretty cheap. Def cheaper than what a mechanics gonna charge you to do it.

It's really easy and if you need any help I'm sure people here can walk you through it.

 

[scoflaw]

Re: On my third mechanic...

Amazing what people beleive.

I believe my eyes. When I bought the boat it had 50 psi on #5, not anymore. Stuck ring or whatever. It's all better now. Go figure. At least I've got an honest dealer who told me to go run it, rather than telling me he would be glad to put another motor in it for big $$$

 

[witenite0560]

Re: On my third mechanic...

It's rare, but I have seen it happen. Usually in a motor that has sat or had little use for years. Rings can get full of carbon, rust, etc. If it does free up, don't be surprised if the compression in the other cylinders improves slightly, too. However, if it's a valve issue and you break a valve, it could leave you stranded and cause further damage.

 

[Bondo]

Re: On my third mechanic...

My questions are - will running it (when I know the compression is low) do any harm to the engine? Is it still worth getting a leakdown test?

Ayuh,... Go ahead, 'n Run it....
At Best, you have a rebuildable core motor at this point,....
It's already Beat, When it finally Pukes,...
Replace it...

 

[Don S]

Re: On my third mechanic...

A stuck ring will give you low compression, like 30-60 psi, but NOT zero PSI.
To get 0 on a compression test, you need a holed piston or a tuleped valve, missing valve head (pushed into top of piston) or the piston not moving up and down.

 

[spdracr39]

Re: On my third mechanic...

It has worked for me also on a car engine. I don't know why people want to say something absolutely won't work when it just hasn't worked for them. Maybe they are so negative because they just aren't very lucky.

 

[fossill]

Re: On my third mechanic...

Considering a boat engine runs very little and sits a lot, there is a big potential for things such as rings to gum up, especially with sketchy maintenance. Using an additive may or may not help. Like I said earlier, you only got 5 bucks at most to lose and be it mine, I'd be trying that well before unloading several thousand on a rebuild. At least then you've exhausted all avenues before departing with your hard earned cash. A quart of Dexron ATF even works great as its high detergent.

 

[NHGuy]

Re: On my third mechanic...

I vote for a dose of snake oil too! I'd put in 2/3 of a can of Seafoam in the crankcase and the rest in the gas. Then run a tank of gas through there, and rechange the oil. Sometimes it works.

 

[bruceb58]

Re: On my third mechanic...

If Seafoam works so well, why not dump 5 cans in? Why not just dump it in the offending cylinder?

 

[lonemust]

Re: On my third mechanic...

I've used mystic mo before with no problem. I have used it to clean the fuel system to loosening sticky rings. And once for a noisy lifter. For the upper end and fuel systems I also use Chemtool B-12. And, Wouldn't it be cheaper to just rebuild the engine you have then to Put a "new" engine in it?

 

[Vanover]

Re: On my third mechanic...

Put in the snake oil and run what you brung. You are 5 bucks worse either way. Whats 5 bucks. it might work. Maybe. Cross your fingers.

 

[dsiekman]

Re: On my third mechanic...

Different problem, but following the concept of "s*** happens when a boat sits"...

When I bought my boat in May she had 160 hours on the ten year old twin 5.0's. The boat had been sitting at the broker's location for almost a year. That means that the other nine years the owner used it less than 18 hours/year. When I picked it up there was lifter noise in the port engine. We changed the oil and at my mechanic's suggestion I took it out and ran it at a comfortable pace (3000-3500 rpms) and treated it as if I was breaking it in again - no extended runs at a single speed, no WFO, etc.

Results? The lifter seems to have "unstuck" itself...or at least it has stopped making noise for the most part. Occaisionally I will still get a tap when I start it up, but it goes away pretty quickly. That said, I still intend to dig into it this winter to see what's up.