No Power

[Lamarg33]

Does anyone know whether or not an exhaust leak can cause a loss of horsepower? My brother has a 9.9 Johnson. Yesterday, we went fishing in his 14ft Jon boat. To get the motor to start, he pulled off the cowling. The motor fired right up; but it hardly moved the boat. Seconds after putting the cowling back on, it died. His 30 pound thrust trolling motor moved the boat better.
According to him, the motor lost its horsepower at the same time he had to start removing the cowling for it to run. He has rebuilt the carburetor, replaced the head gasket, changed plugs, coils, points, condensers, and plug wires. And nothing helped. The compression is 100 pounds on each cylinder.
So, what else could it be?
I appreciate any input.

 

[oldcatamount]

Re: No Power

Do you guys do a lot of slow trolling? If so, the exhaust housing may be loading up with carbon and restricting the exhaust flow.

 

[Lamarg33]

Re: No Power

Yes, the area we normally fish is off of the main channel. The water is choppy. So we use the motor to run alongside the bank.
That makes a lot of sense. We will check it out. Thanks.

 

[mikesea]

Re: No Power

This is an excellent site with alot of 9.9 info.In future posts include the yr.You mention having to change points,s I know your eng would be earlier than 77 ,which I THINK was the change to CDI pointless ignition.Look into doing a decarb.with SEAFOAM.Heres the link
http://www.sschapterpsa.com/ramblings/Ramblings.html

 

[DJ]

Re: No Power

If you have exhaus leaking, under the cowl, that will cause the engine to run very poorly if at all. The first place to look is the engine to mid section gasket. That area can also become clogged.

 

[raczekp1]

Re: No Power

maybe lower unit is bad and gears are blocking drive shaft?
between exhaust and powerhead there is gasket.bad gasket can do this problem,

 

[Lamarg33]

Re: No Power

Sorry about not posting the year. It is a 1967. I really appreciate the the ideas.

 

[ezeke]

Re: No Power

Sorry about not posting the year. It is a 1967. I really appreciate the the ideas.

Are you sure it's not a 9.5HP?

 

[Jerry_NJ]

Re: No Power

Wow, a 1967. In about 1997 I junked my 1986 Johnson 9.9 - but I was told to run it on 100:1 (gasil) and in a few hundred hours, dead "meat".

I was surprised to learn that an ignition problem could cause my 1997 9.9 Evinrude to run with very low power... I think it was running on one cylinder and would after running for a while the other cylinder would begin to fire. A new power pack fixed it up - I mention only as if it is possible for an old style points ignition to cause the engine to fire on only one cylinder it may be worth a check.

Good luck, and congratulation on keep the old engine going. Any idea how many hours it has on it?

 

[F_R]

Re: No Power

Lamar, The 9.5hp motors are notorious for exhaust leaks under the cowling. When that happens, they will run ok with the hood off, but smother as soon as you put it back on. There are several known causes:

1. Seal missing from top of water pump housing. (No longer available from mfr)
2. Shift rod boot torn (No longer available from mfr)
3. Water outlet hose torn
4. Hole corroded through bottom of exhaust manifold
5. Seal flap between the inner and outer mid-section housings.

Except for # 1 and 3, all are major repair jobs. #5 always gets the blame, but usually is not the problem. If it smothers at idle, in neutral, it very may be the problem as the exhaust bubbles up around the motor. But if it smothers at speed, in gear, on a boat, the exhaust is buried in the wake far behind the boat, and is not the cause of the smothering.

No 9.5hp will run worth beans in a barrel with the hood on.