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Low compression

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nicknack2

Regular Contributor
what is the big deal about low

what is the big deal about low compression and outboards? why many mechanics claim that the motor is no longer "fit for duty" after low compression is found on one cylinder??? if the engine runs good and starts and everything why is it that low compression raise lots red flags?
 
That means the motor will neve

That means the motor will never run a full power again. (If at all.) It is on borrowed time at that point. And will quit all together soon.
 
"And ,the tolerances in side y

"And ,the tolerances in side your motor or that cyclinder between piston ,rings and cylinder are now allowing the Piston rings some sideways movement against the wall of the cyclinder which will eventually sooner than later damage your cylinder or if you break a ring could total your whole motor"
 
Outboard motors are a high per

Outboard motors are a high performance 2 stage air processing machine. Air is first drawn into the crankcase. It is compressed and then transferred to the cylinder. It is compressed again there. So a cylinder with poor compression indicates damage to piston / rings or cylinder. Only a fool would think that it will run properly or heal itself.
 
"Besides the obvious facts of

"Besides the obvious facts of cost and so on, it'd be embarassing to row back to shore...

For the peace-of-mind and lower expense, better for an early repair than a whole new motor later. It's advisable to do all the cylinders at the same time, other pistons are possible on their way out too... Motor will vibrate if only one has been done (if re-bored bigger). Did I mention rowing back to shore?"
 
Manuals clearly state that it

Manuals clearly state that it is acceptable to do one cylinder. WISECO pistons are all matched to factory original weight---so a 0.020" O/S is the same weight as a 0.030" O/S piston.
 
"One of the local shops have a

"One of the local shops have a 200HP mercury, they are not willing to do any work on the old Mercuries that I have, they said Im wasting money so they selling me a 200 for $2500 installed, I think I do it I tryied to rebuild the carbs today and all the plugs and the needles were striped in the carbs, it is almost imposible to rebuild the carbs, Im affraid to buy 3 new carbs, throw two new pistons only to find more issues, I went to the lake yesterday after I "tuned" the engines and it was a nightmare getting them to start, then after starting one engine would run at 3000rpm and the onther at~ 4000 then both would quit, I'm done with this two old engines, I will invest in the newer single 200hp, I'm so tire of working and working on this two engines my whole summer is gone and I was not able to run the boat as it should so RIP this two mercuries I'm done..."
 
Tuning and NEW CARBURETORS wil

Tuning and NEW CARBURETORS will not fix an engine in poor condition.How many times do you read here " I rebuilt the carburetors and the engine still runs the same ". People need to trust mechanics or get a book/s on trouble shooting.
 
"yeah, I should had the engine

"yeah, I should had the engine rebuilt to begin with, I had spent $215 on a stator for each engine, $130 on carburator rebuilt kits and fuel pump kits, plus two tanks of diesel driving the boat to the mechanic. I talked to the mechanic yesterday and he says that he also have a 150 hP that he will sell for $1800 + ~200 for the controlers, that is $500 less than the 200hp he offered me(both engines were mede in the 90', but I can't remember exact year modelthe 150 is a yamaha and the 200 is a mercury), my question is would that 150 Hp will be able to plane my 21' 1969 Stamas? you are probably wondering why am I even puting money in this old boat but the thing is that I have already spent about $5500 on it, from tires for the trailer to the initial $4000 that I paid for the boat, the boat is a small cruiser, in rock solid condition, what would you guys do? and also don forget your recomendation on what should I do about the engines should I go with the 150hp of get the 200hp for $500 more?"
 
"Before you go dumping money o

"Before you go dumping money on another used motor - do you have one now?

A rebuild on a V6 may run 2000 bucks all in. That will give you practically a brand new motor.

Dropping 2 grand on either a 10-20 year old motor is just asking for a rebuild in the next year or two.

A 150 should push your rig along quite nicely in the mid 30 mph range (maybe a little better) and would burn about 25% less gas than the 200.

But unless they are offering warranty with either of those motors, you may be better served to have what you have rebuilt, since you have already dumped money into new parts...."
 
"I think my 21' 1969 Stama

"I think my 21' 1969 Stamas which is a walk around weights about 1900 Lbs, I have never been able to find or "pin point" the weight and model type (I think the title and reg. are wrong) because it appears as if Stamas never built a 21 ft in 1969, so I'm wonering if my boat is a little newer, well my question is will a 150 hp be enough to run the boat nicely in the ocean(as Graham Lamb said),because Im planning in taking it to San Carlos, MX (in the Pacific) just right off shore or should I buy the 200 Hp? or should stick with the 150Hp? also I want to use it to ski at the lake."
 
"Here's some specs from a

"Here's some specs from a 150 on the back of a 20 footer with a dry weight of 1800 pounds. Obviously, the 200 would give you better top end, but would also burn more gas all around.

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"
 
"Here's a theory. A new en

"Here's a theory. A new engine costs 12000 dollars.. an old one with a reman power head can be gotten fr nearly nothing plus 2 grand for the rebuilt head. Property taxes on a 12000 motor is going to get you every year, along with insurance if you finance. SPend the money on an old motor, get a like new one, and the property taxes, etc. never come in becasue you are still paying for the vcalue of an old motor even though it is practically new. Same with the boat endl. I wouldn't buy a new boat now that i have found how the older ones can be redone at a fraction of he price. love those old 100 dollar boat and motors."
 
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