Help - 1988 3.7L Bad compression

[kevindineen]

Bought 1988 Stingray last june for $3500. Boat is in great shape. Engine seemed to run fine when I bought it & into this year. I have noticed some wierd things like a loss of power, rough starting when engine is warm, rough idling (some of which was apparent last year too). I figured it was a good time to take it in for a tune-up. Just got a call back from the marina saying the compression was 125/125/50/90. & telling me that it probably would be a minimum of $1000 to get in there & fix, & more likely upwards of $1500-$2000. I'm heart broken. I will miss her if I have ot part her out (which was one of the suggestions from the marina). She runs, & not entirely that bad... can I just use her w/ that compression? I own w/ another person, so we could afford to fix it... but is it worth it? Thankss everyone for your insight.

Mike

 

[kevindineen]

Re: Help - 1988 3.7L Bad compression

my 1st boat. I'd love to keep her.

 

[searay3]

Re: Help - 1988 3.7L Bad compression

hard part here is: without pulling the head and inspecting things, pretty hard to pinpoint the real damage. Paying someone to rebuild is of course going to be expensive. Could be a crack in the head, warped valves, but with two adjoining cylinders being low, could just be a head gasket. Have to consider exhuast manifolds and risers. If you really like the boat and have the interest to dyi it, might be worth it. If your paying a shop, may not be....

 

[kevindineen]

Re: Help - 1988 3.7L Bad compression

Unfortunately don't have the expertise to do myself... nevermind the tools. Having them open it up today & take a look. If you read this, could you cross your fingers that it's just a gasket or a valve... thx.

Anyone ever use the stuff you mix w/ gas that claims to "improve compresson on older engines"?

 

[searay3]

Re: Help - 1988 3.7L Bad compression

There is no 'rebuild in a can', no matter what they claim. If the compression is low there is a physical problem in the head/cyl area and has to be repaired. Long block is another option depending on the condition of the hull, although if a shop is doing the work, not sure what that would save you. It's not all gloom and doom. Have to weigh your options against buying another used boat (who knows if it will last any longer) or a new one..$$$$.
If the hull and interior are decent, fix the motor....

 

[Bt Doctur]

Re: Help - 1988 3.7L Bad compression

The roughness may have been caused by a leaking riser dropping water into # 3 and #4 exaust ports tuliping the valve or cracking it.Minimum is pull the head to inspect.maybe just a valve job and riser is all it needs.

 

[bjcsc]

Re: Help - 1988 3.7L Bad compression

If you can afford to fix then fix it. Only you know if it's worth it. I agree with searay3; if everything else is OK, fix the engine. At least you'll know what you've got when you're finished. Boats require regular inputs of dollars. You got yours for $3500, and split that with someone else to boot. Your boat knows this and is "catching you up".

Bt Doctur: You need to edit a devil into that last post in honor of the count...

 

[kevindineen]

Re: Help - 1988 3.7L Bad compression

Thanks everyone for your input. Should hear back from the mech today. I'm crossing my fingers.

 

[kevindineen]

Re: Help - 1988 3.7L Bad compression

still waiting on mechanic. still crossing fingers.

 

[kevindineen]

Re: Help - 1988 3.7L Bad compression

Another question... She seems to run just fine at any rpm above 750... pretty smooth. could this be an indication of some damage (aka valve) over something worse?

 

[bjcsc]

Re: Help - 1988 3.7L Bad compression

Well?

 

[cobra 3.0]

Re: Help - 1988 3.7L Bad compression

It could be the head gasket, leaking valves, a cracked head, and /or worn piston rings.

The most common problem is the head gasket from overheating the engine usually when the impeller goes and you didn't notice the rising temp. However, anyone or all the above or any combination of above could be the cultprint.

 

[ziggy]

Re: Help - 1988 3.7L Bad compression

ya could try a air leak test to see if ya can determine where the leak is at prior to disassembly. this gave me a clue as to what i was going for on my engine. a head gasket in my case. i had low compression on 1 & 2 also. the leak down test didn't let me know i had a headbolt hole crack that has renderend my block trash.
at least i knew my gasket was blowed anyways, for all the good it did me......i'm still workin on gettin funds for repair myself, .

 

[kevindineen]

Re: Help - 1988 3.7L Bad compression

Ok, so here's the deal.

I talked to the owner & he seems to think that it's rings or valves. They did a wet compression test & the pressure didn't come up at all, so I would think that would rule out rings... (which woudl be great).

In the meantime... I've got a bunch of buddies coming up this weekend (one with a new stingray 20') to go camping on woods island up here on Lake Champlain, so I'm putting her back in the water friday, going to ease her to the island (no skiing, or hammering on the throttle) because we need the packing space w/ 6 somewhat portly beer drinkin dudes. I think (hope) I'll be ok. The mechanic though I'd prob be ok too. I figured what the 'f. I'll get to the island & then we can use my buddys boat for skiing...etc. She seems to run ok once warm, & at a cruising speed (1000-3000 RPM). So that's the skinny. I really don't know anything as of yet. But I'm going to bring her back in on sunday & I'll have them open her up on monday or tuesday. Should know more then. I'll keep y'all up to date as it seems you are on the edge of your seats... Just kindding, though I do appreciate the interest & support... cross your fingers for a safe return! red sky at night.

 

[kevindineen]

Re: Help - 1988 3.7L Bad compression

The owner of the marina that is...

 

[ziggy]

Re: Help - 1988 3.7L Bad compression

kevin, i wish i would have just used my boat too. it was already broke just like yers. but it still ran. so i would go for it. worst ya can do is break it so that it'll need a new engine. sounds like ya got another boat to tow ya home anyways.
here's some info on the leakdown test that helped me figure what was wrong with mine. even though it was only partly right. and the part that was wrong would not have shown up under any test short of looking at it..... check this out.

http://www.boatfix.com/merc/Bullet/97/97_25.pdf

 

[bjcsc]

Re: Help - 1988 3.7L Bad compression

OK, preface this with the fact that I may be somewhat paranoid about getting raked over by "imposter" marine mechanics , but this is starting to sound a little bizarre. If you run a compression test and get a low cylinder, you would immediately follow with oil (wet testing). You're already there, all set up... As said, if adjacent cylinders could be a head gasket but there would be other symptoms. "Seems to think it's the rings or the valves..." Really? What an amazing deduction considering with the head gasket ruled out there isn't anything else it could be...My observations are as follows: 1) This mechanic is not building rockets in his spare time and 2)You would be wise to either a) do a leakdown test yourself before taking it back in or b) start practicing your barrel stance.

 

[Chopstix99]

Re: Help - 1988 3.7L Bad compression

I run a pair of merc 488's which is a hybrid of the 470/3.7L engine. I had one of mine come apart last summer. I found a used boat parts yard / shop {boat graveyard} that sold me a used engine installed. They took a 470 and put my exhaust and intake manifolds on it along with the other 488 specific items off of my old engine. They charged me 1750 out the gate with a full one year warranty on the engine. Really not a bad price IMO and the thing still runs like a champ.

I live in the southeast corner of Michigan on Lake Erie so we have a few of the 'yards' around here. They aren't advertised in the yellow pages or anything and aren't really easy to find. Ask around marine repair shops and marinas and stuff, they are pretty much located word of mouth. But if you live near water with a lot of boats, they are definitely out there. Just like a car goes to a junkyard, boats need a final resting place too. I have used them for a riser, a heat exchanger, small stuff like gauges, plus the whole engine. A good way to save some $$ if the boat doesn't warrant sinking a lot of cash into.

 

[DHPMARINE]

Re: Help - 1988 3.7L Bad compression

Once you pull the head you will know a whole bunch more. About using the boat until then .........

My buddy CWHenry says :What could possibly go wrong with this plan ?"

We know.

Good Luck.

DHP

 

[kevindineen]

Re: Help - 1988 3.7L Bad compression

Thanks y'all w/ the comments/suggestions. I'll be picking her up tomorrow to take out on the camping trip. I'll report back as to how she runs. Just talked to the guy at the marina, by the way, he's a boyfriend of a girl I work with, so I pretty much trust him, bjcsc, believe me I'm suspect of mechanics whatever it may be, but I think this guy is beiong straight up with me. He said they did a compression test & a compression test w/ oil & that the pressure came up slightly & he thinks that it's still rings, a scored piston wall... I'm hoping he's wrong, & it's valves or head gasket...