Terminology Questions.....???

This forum is great! Im learning so much and enjoy it. Ive been reading threads for hours just because it interests me even though the thread does not pertain to the issue I am having with my outboard.

So Ive come across a few terms I dont understand. Yes, I could google them but I'm sure you pros would have a much better explanation.

So apparently there are two kinds of outboards. "loopers" and "crossflows". What does this mean and what are the differences and pros/cons? How can I tell which one my outboard is?

Secondly, Ive read and seen several threads mentioning "reeds" in regards to the carbs. What is this and what do they do?

Thanks. Im hungry for knowledge.

Re: Terminology Questions.....???

Only stupid question is the one not asked as the saying goes....

Im no pro, but will try my best to explain without using too many big words that need more explaining, lol.

The reeds, or leaf plates, are a one way check valve per se. They must seal the crankcase pressure or the air/fuel mixture will be pushed back through the intake (carbs) and then "spitting" fuel outwards, which you may notice if you remove the carb face plate.

They allow the air to be sucked in through the carb to the crankcase during piston movement, yet seal it tight during combustion.

Cross flows have an irregular shaped piston top. It is called a deflector. This deflector directs the incoming air/fuel up, towards the top of the cylinder. This creates a wall or column of fresh mix that sweeps across the cylinder towards the exhaust ports. As the column advances it pushes the spent exhaust gases out of the exhaust ports.

Loopers have a near flat piston top. They dont use deflectors like cross flows, however they have shaped intake ports and combustion chambers to control the scavenging of the cylinder. Several intake ports are aimed upwards and arranged such that their combined streams flow upward and then LOOP down toward the exhaust ports.

Cross flows are typically better at low speeds or idle, whereas loopers are better at highter rpms and have better fuel consumption due to the lighter pistons.

Hope this helps some, hopefully someone else can clear up anything that I missed.

Re: Terminology Questions.....???

At full throttle, the pistons are reciprocating back and forth at speeds of up to 12,000 strokes per minute. At the end of each stroke, that piston must come to a complete stop and reverse direction. So, you can imagine the forces involved and what a difference weight makes. That is one big advantage of loop charging and their lighter pistons.

Of course, the obvious advantage is better performance and fuel economy.

That is not to say that cross-flows are obsolete. They have been pretty well perfected over the last 100 or so years.

Ever hear a chainsaw scream at 10,000 RPM with no load on it? Loop charged/light piston.

Think of reeds as a door. Wind sucks or blows door open and goes through. Reverse the wind direction and door slams shut and no air goes through. Same thing in an outboard. Air/fuel goes in but can't blow back out. Very simple and reliable form of a valve.

Re: Terminology Questions.....???

If you post your engine year, hp, and model number, that will help to identify just which you have.

Re: Terminology Questions.....???

Well said Gentlemen!... even I can understand that

Re: Terminology Questions.....???

Hmm ok, thanks for the free knowledge. Do all engines have reed valves? If not what is used to prevent blow back? None of this pertains to the problem Im having with my engine but its good to know. Im having a problem with fuel delivery/fuel pump/carbs. Im trying to diagnose and think I may have found the issue. After pumping the primer bulb over 100 times it never got hard. After checking for air leaks I found nothing. I then traced the fuel lines and found that where the fuel line crosses thru the hull and come up into the backwash area that it was kinked due to the 180 degree turn the line has to make. Fixed it and the primer bulb got hard within 10 pumps. Have not tried to run on muffs yet to see if the kink was the issue.

My engine model is J88MSLCUS. SN 7484712. I believe it to be a 1988 88 spl. Can anyone confirm this? Also what does MSLCUS in the model number indicate?

As always, thanks for your replies.

Re: Terminology Questions.....???

Sounds like you may have found the problem!

Re: Terminology Questions.....???

kurtaiden said:

Hmm ok, thanks for the free knowledge. Do all engines have reed valves? If not what is used to prevent blow back? None of this pertains to the problem Im having with my engine but its good to know. Im having a problem with fuel delivery/fuel pump/carbs. Im trying to diagnose and think I may have found the issue. After pumping the primer bulb over 100 times it never got hard. After checking for air leaks I found nothing. I then traced the fuel lines and found that where the fuel line crosses thru the hull and come up into the backwash area that it was kinked due to the 180 degree turn the line has to make. Fixed it and the primer bulb got hard within 10 pumps. Have not tried to run on muffs yet to see if the kink was the issue.

My engine model is J88MSLCUS. SN 7484712. I believe it to be a 1988 88 spl. Can anyone confirm this? Also what does MSLCUS in the model number indicate?

As always, thanks for your replies.

Click to expand...

your motor is a 1987

I think all the 88hp specials were cross flows...

the M indicates the block design I think, your being a 90 degree V cross flow
the S usually indicates the motor is special in some way..

could either be a SPECIAL, or an optional white color paint job, or a named motorm like ocean pro, ocean runner, fast strike ect

the L indicates it has a long shaft which is 20"..it could have been an X( extra long shaft) then the shaft would be 25"

the next two letters indicate the year, based on a formula that is described as

INTRODUCES... the letters each represent a number 1-0
1234567890

c=8 and the u=7 on your motor
cc=1988
ce=1989
si=2001
ee=1999

ect the last letter is manufacturing code i think and is not used to determine what model you have

it is good to learn teminology so you can ask the right questions and understand the answer...and get the best help you can

good luck

bob

Re: Terminology Questions.....???

Sorry to lose a year on you, but its actually an 87....

Here is a top secret page, shhhh, dont tell anyone.

http://www.skoterskroten.com/img/arsmodellstabell.pdf

Scroll down to the second page

Re: Terminology Questions.....???

HighTrim said:

Sorry to lose a year on you, but its actually an 87....

Here is a top secret page, shhhh, dont tell anyone.

http://www.skoterskroten.com/img/arsmodellstabell.pdf

Scroll down to the second page

Click to expand...

you are quick high trim!!!!!!!!!! ha ha ha

nice page

Re: Terminology Questions.....???

I havent had a coffee yet, my mind was thinking 87, but my fingers wrote 88, lol, I quickly changed it. Even stated that he was losing a year, yet still wrote 88, lol.

Re: Terminology Questions.....???

And MS in the model number is for "Manual Tilt - Electric Start / Special" as distinguished from M alone.

Also, BRP keeps their model list on their website as well: http://evinrude.cust.shopatron.com/media/document/ModelNumberReference.pdf

You can always access it from the parts catalog page.

Re: Terminology Questions.....???

ezeke said:

And MS in the model number is for "Manual Tilt - Electric Start / Special" as distinguished from M alone.

Also, BRP keeps their model list on their website as well: http://evinrude.cust.shopatron.com/media/document/ModelNumberReference.pdf

You can always access it from the parts catalog page.

Click to expand...

I ahve always wondered about ALL those different models, but when you look up motors they dont give you that many to choose from... a specific contradition on that chart involves my motors

J115SLEOC

they say the SL means 60 degree V .. and I have SL but I have always thought the L means LONG shaft and the S was for special styling
theoretically my model should read J115SLLEOC

I had a V in the model number of one of my motors a 2001 50 hp..johnson

the chart says it means it had a special gear case...it sure was special it self destructed 4 times!!!!! ha ha ha



hmmmm


bob

Re: Terminology Questions.....???

Back to the question asked, "do all engines have reed valves?". Well virtually all modern two-stroke outboards do. You may find a 3rd port one somewhere yet. Many chainsaws are 3rd port. With a 3rd port design, the piston acts as the valve. Go gack far enough and you will find rotary valves, and poppet valves. But we are talking antiques there. Old 5hp Johnsons had BOTH 3rd port AND a rotary valve.

Re: Terminology Questions.....???

Outboards need reed valves since they normally place the carbs at the base of the crankshaft.

2 Cycle Motorcycles can use the piston skirt as a reed valve, when they place the carb on the cylinder neck. Some Motorcycles have a rotating disk "with a window", on the crankshaft, to act as a valve. In this case the carb is next to the crank, under a side cover.

Re: Terminology Questions.....???

Snowmobile mtrs also used this same design. If I remember right the old Martin outboards used a poppet valve design.