Low compression

I bought a used boat with a 1995 evinrude 88hp. #1 cylinder has 75# compression and the other 3 have 110 to 115. How bad can it be to repair? Think I might get lucky and it be a head gasket? I just didn't plan on this.

#1 is often a casualty of lean mixture, sorry, Roy.....
probably not a gasket. Crank seal can go here too, also creating lean.

My bet is you will find a damaged piston / broken ring.-----Classic failure.-----It will happen to all those motors !

Pull the head before you do anything else.

Lesson one. Always do a compression test before buying a motor. I bring my gauge right into the pawn shop its all in good practice. "Wisdom is knowing what to do, discretion is knowing when and where to do it." Proverbs 3:21

Yes I'll do that first. Maybe get lucky, but I doubt it.

Sorry having droid navigational issues. I appreciate your alls input. I dread pulling this thing apart. Is Clymer a good repair manual?

Thanks again I'll keep you posted as I go.

Roy.... As "Boobie" states.... Remove the cylinder head before going any further.

You have a compression difference of 40 lbs (not good at all!). Head gasket??... possible but not likely.

More likely a blown piston... major overhaul... complete tear down... much $$$. Let us know what you find.

The previous owner... curious... What did he have to say about this engine that would cause you to close the deal?

Blown pistons is very common.------Took one off the boat at a dealer before the shop installed a new motor.-----Sold it with one phonecall a few days later even before I rebuilt it.

The person i bought it from buys and resales used boats, sort of a side job for him. He started it up when i was there and it ran great. I noticed that registration expirded 2 years ago, and he said the owner stated that he lost interest in it. The seats, and hull looked in great shape with very little use. The carpet was replased and in great condition.

My wife and I took it out after i drained the old varnished gas out and replased most fuel lines. I had trouble getting the fuel pumped up to motor, but once I got fuel pumped to carbs it started right up. Took a while to get it running good and smooth out. We ran around the lake for hours. We would stop and idle and sometimes shut it off and float around for 15 or 30 mins. I figured it would need some attention, but it ran great. We ran out about 8 gallons of fresh gas with 50 to 1 oil mix and I put some seafoam cleaner in with gas.

We went back out last week and it was awful. Hard to start and when we got it up on plane it died after a few seconds.

Pulled head, piston edge chewed up. Cylinder walls feel smooth. I send this then post pictures. This is 4th time typing this, my lack of knowledge.

Personally I think the engine was in bad shape when you purchased it but it was patched up just enough to impress you. Unlikely that damage would be done in one outing... possible, but more likely that, although you thought the engine was running great, the compression was failing and the owner wanted to unload it as it was slowly degrading into what you have now. Unfortunately there's no way to prove that that I know of and you're stuck with it. Hopefully you feel like you got a steal and can absorb the loss.

Back when I was a working man and the labor rate was about $20.00 per hr and parts weren't made of gold and platinum, that overhaul would cost you roughly $2000 to 2500... but now I hesitate to even guess. I can only wish you luck.

Joe, that must have been half a century ago. Most shops around here are 100 bucks per hour. I'm still at $60, work right at home and walk out to work with my coffee cup in hand. Got more money than I need. Roy, sounds like you got a nice rig. Can you rebuild it yourself? If you can go stock piston......no oversize, gonna be a fun job. Better check out those carbs, could have been running lean.

I don't know if he knew or not. We love the boat it's a Javelin 360fs. Going to pull powerhead in next day or so, crappie biting need to get on the water.


Is Clymer manual good for what I'm doing, or should I purchase a different one? Going to check other 3 cylinders and if ring gap is in spec, I'll hone and install new rings. #1 is a different story. Maybe time for machine shop. Thanks to your alls input and advice. I really appreciate it. I'm just having trouble with posting on this site.

Your doing good, that is a sweet boat, brother. Clymer should cover what you need, I have a few here too, I do plenty automotive stuff as well. For photos gotta reduce size to around 1000K. When you build your own stuff its a good feeling to use it and rely on it rather than cuss somebody elses mistakes. Love Crappie too, my wife prefers Sunnys, Pumpkinseeds and Bluegills, they have a different flavor. Any fish is good for me, even Eel pout.

Putting new rings in worn out ring grooves may well be a mistake !-----4 new pistons is what you need.

Roy... I wonder why you're having a problem posting. This is the most perfect and easiest site to work with in my book. However, whatever problem you're having, we appreciate you sticking with us and hope the difficulty is a momentarily thing.

Tim... The $20hr labor thing mention... No, Not a century ago but rather that was back in the 1980's. However, how about a starting point back in the early 60's when some customers got a little upset about the $4 labor charge? BTW, I had a 1959 Ford Edsel Wagoneer (station Wagon) back then.

I try pictures after I resized them. I think this one made. Timguy was correct.

Racerone, I thought about that. When I get it disassembled and the manual, I thought since I work on race pistons for Nascar and stuff, I have the gauges to check ring goose width and depth. I do anodize top ring groove on performance pistons. So maybe I can work with the other 3 pistons? My boss would flip, if he caught me. The cost of this is increasing drastically
Maybe cheaper to buy new or rebuild powerhead?

In all seriousness, how bad does it look?

Well I see that damage all the time !!------That will happen to all of those motors.----Needs 4 new pistons.

RoyBrew said:

In all seriousness, how bad does it look?

Click to expand...

That type problem is usually caused by a fouled carburetor... one cylinder running too lean, however, it could also be due to a weak (or no) spark on that cylinder resulting in what we call a "wash out" condition. Either situation will tear a piston up.

The exact scenario can't be known until the powerhead is completely torn down pertaining to the pistons and cylinder walls... boring, sleeve replacement, etc.

What is known is that at least one cylinder needs boring O/S along with the O/S Piston. The other three = ? until final tear-down. One cylinder head, Failing ignition components = ?

Common parts = spark plugs, piston rings, PH gasket set, carburetor kits, Water pump, Thermostats, Gear lube, spray paint.... and there's always the unexpected, "blue" bearings to name one... there will be others.

Average labor time = 24hrs, includes run out, adjustments, etc.

The cylinder head replacement... if when cleaning the head of all the piston rings particles embedded in it, one little sliver is missed... that sliver will glow like a glow plug of a model airplane engine which will result in pre-ignition that'll melt a piston in a short amount of time... not worth the gamble.

NOTE: The "spray paint"... Always, when the powerhead is assembled, including cylinder heads and intake manifold... paint it to restore its appearance to new condition, otherwise, it has a patched up look (ugh!).

Those are words of experience, I suggest you try to follow them. Just going on pictures, but when the other pistons are out, we will of course know more. If the bores check out you still might be able to go stock pistons, but that piston is heavily damaged and its unlikely the bore can survive without oversize.

What can I expect with regard to machine shop labor for honing 3 cylinders, and cutting one cylinder .030 OS? This is east tn and the cost of living is lower then most states. Just curious a rough estimate of what to expect. Maybe best case senairio.

What is an Exhaust Filler Block Replacement kit?

What about the retainer needles (bearings)? Are these just automatically replaced or are they first checked for wear?

I plan on getting PH pulled and torn down tomorrow morning. The manual should be here beginning of week, then I can take pistons to work and do some measurements and more indepth inspection.

Thanks Racerone, joereevez and Timguy. Your teaching me things I never realized. I think 2 strokes are more complicated then 4 stroke car engines. I agree I need to change pistons and rings. I am curious if I can determine how much wear there is on the motor by checking the dimensions on the piston ring grooves.

Sorry they are simpler than 4 strokes.----But they are hard working / stressed engines and everything must be correct,

Thats right, firing every stroke puts continuous stress on most components. I would never bore just one cylinder, however. Imagine the imbalance created with the rotating assembly. Also the larger bore will produce more power on that cylinder, perhaps negligible, but nevertheless to be considered. Not sure what the other techs think of that but we are turning 6000 RPM steady. My builds are in complete synchronicity and balance. Never had a return and I have built hundreds, but that includes motorcycles, cars, trucks, IO's, and huge inboards. Machine work 40 to 50 bucks a hole. Bearings are usually good to reuse.

Regarding the manual. Get a factory repair manual. I had that same engine. It was great until I could not get the lower unit off to repair the waterpump (shaft splines stuck to the head). The factory manuals don't leave anything to be guessed like the aftermarket ones. Good luck!

Ok trying to get picture to loadload wow this things slow. Got #1 piston out. Yuck! Worse than I thought. Can this or does it need to be re-sleeved?

Very common problem simply because of the design of the top piston ring !!-----I see this damage all the time.----Hard for some folks to understand what happens inside one of these engines !

I take it your not a fan of this type of design? Should I scrap this motor? Or is it fixable? I think I feel a big pit in my gut.

I appreciate your advice Racerone.

I think they are a great / simple motor.---Ruined by folks who do not understand 2 stroke engines.----And I do not understand why they kept that ring design for so many years.----Rebuilt my first " pressure back " ring motor in 1981 If I recall.----Measure the cylinders and bore / repair as required.----Will run properly for many years.

RoyBrew said:

I take it your not a fan of this type of design? Should I scrap this motor? Or is it fixable? I think I feel a big pit in my gut. I appreciate your advice Racerone.

Click to expand...

I'm going to jump back in here momentarily with my opinion.........

For many years... from day one of OMC to somewhere around 1972 there were three (3) rings on each piston, all of which were of the rectangular shape if you looked at the end portion of any of them... and that seemed to work fine. Then in 1973 the two (2) ring piston came upon the scene... with the top ring being beveled. I assumed the bevel was designed to have the combustion force the ring out sideways, against the cylinder wall, to help the compression psi.

That seemed to work fine also... Until some idiot redesigned the pistons to have the top ring edge just a few thousands from the top of the piston that resulted in only God knows how many blown powerheads. Fortunately what has been known as the dreaded "High Ring Piston" became a thing of the past very quickly and the ring grooves on the pistons dropped to their former position... however, to this day, they remain a two ring setup incorporating a top beveled ring.

Myself... I think that the beveled ring serves a purpose (compression increase) but is it really better than the three ring setup? To make a definite choice as to which is better... I'd have to see identical engines tested with the only difference being the piston and ring setup... Two vs Three ring. I don't think that's going to happen.

As to what to do Roy... fix or scrap? The thing to do, only way to decide really, is to tear it completely down, inspect and have the damaged parts "here" and the good "there" so you can figure the cost of parts plus the machine work... then add at least $2500 for labor to that unless you're going to do it yourself... BUT still... that's a lot of work and your labor's worth something (pick a figure). Then, after you figure the total cost... match that against a replacement you have in mind. You might want to throw in the time lost fishing, skiing, and all around general boating lost while that engine's tied up with repairs. Wish you luck.