125 hp force low power in forward good power in reverse

Mikkohart

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Joined
May 22, 2013
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17
Dear all

Would you be able to help?
I have 1989 Bayliner 1950 with Force 125 outboard (1251x9B). I have had it 2 years and never got it run well.
Motor starts up and idles well but gives only 2600 rpm when putting full throttle forward. After minute or two it planes and can get it to 3500 rpm when trim all up. When putting it in reverse it gives easily 4000 rpm and over.

I had it looked over in a shop and they found compression all good and also cleaned the carbs. They changed the CDI boxes but none of this helped.

I rebuild the fuel pump and tested with external gas tank without success.

Appreciate all help and ideas!
 

pnwboat

Rear Admiral
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Oct 8, 2007
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Re: 125 hp force low power in forward good power in reverse

What is the diameter of the propeller and the pitch of the blades?
 

Jiggz

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Oct 23, 2009
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Re: 125 hp force low power in forward good power in reverse

Have you verified the position of the throttles in relation to the control handle? It sounds like the throttle is not centered with the handle. Full forward position of the handle equals horizontal position on the throttle (or butterflies). Don't confuse the choke valves with the throttle valves which are located way behind the carbs or right there by the "throat". Read the link and synch sticky posts.
 

Mikkohart

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May 22, 2013
Messages
17
Re: 125 hp force low power in forward good power in reverse

I have 13 1/2 x 19" prop
 

Mikkohart

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May 22, 2013
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Re: 125 hp force low power in forward good power in reverse

The butterflies open all the way when motor is not running but have not checked while running. I did have friend checking that all links move to fully open position while running and they do
 

pnwboat

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Re: 125 hp force low power in forward good power in reverse

Well that propeller is probably the highest pitch that you would use with your particular set up. A 17 pitch prop would work better, however, even with the 19 pitch propeller, you should be see more than 3500 RPMs.

Start out with the basics. It appears that you have done some of the basics, compression, CD modules, fuel pump. Make sure the throttle plates in both carburetors are moving in "sync" when you move the throttle handle. If one is opening farther than the other, this needs to be corrected. Make sure that the throttle plates are pretty much horizontal when the throttle handle is at maximum speed.

While the motor is at idle, temporarily disconnect each of the spark plug wires, and re-install it. The idle speed should decrease each time you remove a spark plug wire. If you remove a spark plug wire and it has no affect on the idle speed that may indicate a problem with that particular cylinder. Possibly an ignition problem.

Check the spade lug connecters on the stator wires, and the trigger wires where they connect to the 12 position terminal block. The is usually a small piece of black heat shrink insulation covering the crimped/soldered wire connection. Sometimes the wire strands break inside the black heatshrink insulation and you cannot see it.

You can also check the resistance of the stator itself. The stator generates the voltage to fire each of the ignition coils. There are two sets of Blue and Yellow wires from the stator. Disconnect each pair of wires and you should measure 680 - 850 OHMs. The resistance of both sets of Blue and Yellow wires should be within 5% of each other.
 

Mikkohart

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Joined
May 22, 2013
Messages
17
Re: 125 hp force low power in forward good power in reverse

Thank you! I will check the stator next, spark seems to be ok.
 

Jiggz

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Oct 23, 2009
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3,817
Re: 125 hp force low power in forward good power in reverse

If there is no sign of misfiring at all, I can only think of timing or fuel delivery system. Carb float adjustment or position can also affect max rpm.
 

Mikkohart

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May 22, 2013
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Re: 125 hp force low power in forward good power in reverse

Haven't had time to check the the stator readings. Today I did a test drive and after that was checking the prop and noticed that there was no exhaust snout (not sure what to call it)?! Am I loosing it or shouldn't there be a adjustable plate there in this model 1251x9B? If so would it have major impact on performance?
 

Jiggz

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Oct 23, 2009
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Re: 125 hp force low power in forward good power in reverse

The lack of exhaust snout can cause serious cavitations allowing higher RPM with lesser "push" this is probably the reason you have higher reverse rpm than forward. But that doesn't still address the original problem why you cannot get more than 3500 RPM in forward gear. Have you tried running the engine with the cowl remove to see if that changes the max RPM in forward gear? I'm thinking you might have a serious exhaust recirc'ing to the carbs due to a torn relief hose to the nostrils or idle relief vents.
 

Mikkohart

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May 22, 2013
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Re: 125 hp force low power in forward good power in reverse

Thank you, I have run the engine without cowl but did not see any difference. Engine does not smoke much except when starting with high idle. Most exhaust comes under water and some through nostrils. Ordered new stator and 17" prop and will try if those help.
 

pnwboat

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Oct 8, 2007
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Re: 125 hp force low power in forward good power in reverse

Like Jiggz said, the missing exhaust snout will prevent the propeller from generating sufficient thrust. It's not even worthwhile to do any testing in the water without it. It's very important to have the snout installed otherwise you'll experience poor performance. Did you get a chance to check the stator resistance?
 

Mikkohart

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May 22, 2013
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Re: 125 hp force low power in forward good power in reverse

Ok. I bought a multimeter but need now to learn to use it =). Will have help during weekend. Do I need have the engine running while measuring, noticed that it shuts down if any blue or yellow wires are disconnected while running.
 

pnwboat

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Re: 125 hp force low power in forward good power in reverse

You check the stator wires by disconnecting them with the motor turned off.
 

Jiggz

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Oct 23, 2009
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3,817
Re: 125 hp force low power in forward good power in reverse

Ok. I bought a multimeter but need now to learn to use it =). Will have help during weekend. Do I need have the engine running while measuring, noticed that it shuts down if any blue or yellow wires are disconnected while running.

Those blue or yellow wires provide power to the CDM, obviously when disconnected will turn off the engine. Since there is no sign of misfiring (unless you diagnose wrong) you can try doing the resistance check (between blu/Yel wires) which should be around 680-800 ohms. You need to ascertain you do not have misfiring at all speeds or RPM's. Verify compressions for low compressions could mean the engine lacks power and require rebuilding.
 

Mikkohart

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Joined
May 22, 2013
Messages
17
Re: 125 hp force low power in forward good power in reverse

Hello, sorry for late update! The stator was replaced and now the boat takes off and planes easily. I changed to 17" prop and now the top rpm is 4500 and speed 27 mph. I might still miss some power but seems like stator was one of the problems.
 

Mikkohart

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May 22, 2013
Messages
17
This summer I learned how to replace the reed plates and now get 5500 RPM and 36 mph.
 

pnwboat

Rear Admiral
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Oct 8, 2007
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4,251
There you go. 5500 ROM's is more like it. Sure beats the 3500 you were getting when you first started. Good job!
 
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