Force '89 125hp lacks power and top end speed

[The Force power]

Force power, The plugs are new and the spark test showed a good spark at 9/16". The Re-circ system test is next. I assume that consists of just spraying carb cleaner around all components and mating surfaces on intake related parts? Also, is there a preferred motor speed for trying the Re-circ test? Thanks.

To inspect Clean the Re-circulation system (hoses/check-valve/screens) you may have to flip the bracket of the ignition)
on the same side as your ignition packs/ coils are you see a few thin hoses running remove one by one!!
(so you don't mess up the order)

There's are "dog-bone" shape covers and a screen behind it check & clean as necessary (also clean the internal passage in the cover)
823715.pdf

check on page 26

 

[Gearhard]

To inspect Clean the Re-circulation system (hoses/check-valve/screens) you may have to flip the bracket of the ignition)
on the same side as your ignition packs/ coils are you see a few thin hoses running remove one by one!!
(so you don't mess up the order)

There's are "dog-bone" shape covers and a screen behind it check & clean as necessary (also clean the internal passage in the cover)
823715.pdf

check on page 26

Force power, Thanks for the info, but there is no connection to the pdf file you sent, and I don't know what page 26 would be.

 

[Gearhard]

There’s a set screw which screws into a metal clip which connects the two carbs; so they open simultaneously( in my case; my top carb butterfly needed to be ever so slightly adjusted forward of my bottom). I know it sounds crazy but it calmed the beast, hole shot and in forward idle gear are significantly much better. If that makes any sense

puffitu, how were you able to determine that you needed to make that adjustment?

 

[puffitu]

Trial and error...luck...frustration and patience. Again, that was in my case. Most guys here will probably say it’s crazy but in my case it worked-maybe the previous owner jammed something into the carbs and bent the flapper; who knows, all I know I had to do that to make it run better. These are good old motors-I love them

 

[The Force power]

Force power, Thanks for the info, but there is no connection to the pdf file you sent, and I don't know what page 26 would be.

It should work??
I send it from computer & I tried it at home on my PC and it works
Try it now

823715.pdf

SORRY!!! they're on on the opposite side

 

[The Force power]

puffitu, how were you able to determine that you needed to make that adjustment?

Part of the link & sync.
Did we not tell you to this first

 

[Gearhard]

Part of the link & sync.
Did we not tell you to this first

Force power, this is the message I get clicking on the pdf link. I have done a link and sync and adjusted that linkage but I made them open the same amount simultaneously.

"Invalid Page URL. If this is an error and the page should exist, please contact the system administrator and tell them how you got this message."

Not sure why it's not jumping to that page. I assume the dog-bone covers are the ones under the fuel pump?

 

[The Force power]

They're not directly under the fuel pump

 

[Gearhard]

They're not directly under the fuel pump

Force power, ok, I see there are port covers and drain covers. The drain covers are more dog-bone, and the port covers more trapezoid. I'm thinking both types may need to be removed and checked. Hoses run from port cover approx cyl 1 to cyl 2 drain cover, and cyl 3 to cyl 4. I would like to be sure before I disassemble so that I can get replacement gaskets. Some gaskets don't seem available, so do I have to make my own? Do I also need to remove the port covers or just the drain covers? Thanks for your help.

 

[The Force power]

Force power, ok, I see there are port covers and drain covers. The drain covers are more dog-bone, and the port covers more trapezoid. I'm thinking both types may need to be removed and checked. Hoses run from port cover approx cyl 1 to cyl 2 drain cover, and cyl 3 to cyl 4. I would like to be sure before I disassemble so that I can get replacement gaskets. Some gaskets don't seem available, so do I have to make my own? Do I also need to remove the port covers or just the drain covers? Thanks for your help.

Funny!! I have not heard the word trapezoid since high school


The "drain cover(s)" are to be removed & cleaned (screen(s)
The "port covers can stay!! , just remove elbow-fitting(s) & other straight fittings (some are check-valves for inspection/cleaning

Make sure you note the sequence of the hoses & fittings; do a set at the time

The gaskets "usually" stay on either the cover or block, use a sharp putting knife to ensure the gasket stay or come off on one side only

 

[Gearhard]

The "drain cover(s)" are to be removed & cleaned (screen(s)
The "port covers can stay!! , just remove elbow-fitting(s) & other straight fittings (some are check-valves for inspection/cleaning

Make sure you note the sequence of the hoses & fittings; do a set at the time

The gaskets "usually" stay on either the cover or block, use a sharp putting knife to ensure the gasket stay or come off on one side only

Done, covers removed and components cleaned, although they were not what I would think is called "dirty". Not sure if screens needed be removed from covers for cleaning, so I just cleaned them in place rather than dislodging them. Hoses showed a little age related cracking, so they were replaced, even though they didn't look to be bad enough to leak. Anyhow, another test needed to judge effect of cleaning.

 

[The Force power]

Done, covers removed and components cleaned, although they were not what I would think is called "dirty". Not sure if screens needed be removed from covers for cleaning, so I just cleaned them in place rather than dislodging them. Hoses showed a little age related cracking, so they were replaced, even though they didn't look to be bad enough to leak. Anyhow, another test needed to judge effect of cleaning.

The Screens can stay in place (the chunks are on the out side anyways) just make sure the passage ports are cleaned.
The cracks in the hoses is usually the black paint but good job on replacing the hoses regardless

 

[Gearhard]

Water tested the motor today with mixed feelings. The motor idled well and ran smoothly thru the full throttle range. Out of curiosity I changed the prop from 15P to a 17P with expected results, hole shot got worse and WOT RPMs dropped about 600 RPMs. It took about 100yrds to plane and maybe 200yrds to hit max RPMs. Problem being that max RPMs at WOT only achieved just under 4000 RPMs. Max GPS speed was 32mph. I'm sure that another 1000RPMs would get me close to 40mph and I would be fine with that. Overall, the motor sounded very good and was smooth and even, but low top end speed. Is 5000 RPMs too much to expect out of the motor? Tomorrow I'll do another compression test, just to verify all is still right at 150psi. Does anyone have an idea why this motor seems to under-perform? Thanks.

 

[The Force power]

A 17 P on a 125 HP should be running WOT at 5500 easily but what seize / weight is it moving?

 

[Gearhard]

A 17 P on a 125 HP should be running WOT at 5500 easily but what seize / weight is it moving?

Force power-my boat is an 18" CC Wellcraft Fish. Spec sheet lists it at 1740#.

I verified the RPMs with tach/timing light and dash tach matched. Verified throttle plates horizontal at WOT. Verified timing at 28° static and was 30° dynamic. At least 3/4 tank was fresh fuel. Spark test jumped 9/16" gap on all cyl with bright blue spark. Linked throttle roller between marks on throttle cam disconnected from tower. Compression on all cyl 150+/- 5psi. Replaced Stator 3yrs ago. Rectifier recently replaced with voltage regulator, running around 14V WOT.

I am running out of ideas on things that could be causing low RPMs, and afraid thing causing it could cause other problems, ie. burned pistons.

Do the idle jets contribute fuel at WOT? Wondering since turning instructions warn of running too lean after carb adjustment.
Could PO have changed main jets? Is there a way to check for correct main jets?
Unsure of what to check next or how to proceed.

 

[The Force power]

My boat is an 18" CC Wellcraft Fish. Spec sheet lists it at 1740#.


Do the idle jets contribute fuel at WOT? Wondering since turning instructions warn of running too lean after carb adjustment.
Could PO have changed main jets? Is there a way to check for correct main jets?

-The motor should easily handle the boat.
-IF the air/fuel mixture screw set too lean & damage/melt piston(s) at WOT is debatable?!?! some experts say yes & some say no AND I'm not an expert!

- Jets There were a couple dozen different carbs used on those motor.

Find carb part number, like
tc119a
tc107a
tc138a

MAIN Jet sizes for a 3 cylinder motor with 3 carbs are .070, .074, etc.

MAIN Jets for a 4 cylinder with two carbs are larger, .092, .094, etc.

Id the carb, then verify the correct jet installed for your altitude.

you can sort through all the carbs, and the corresponding jets per altitude, on
the mercruiser parts dot com web site.

Note, the top/middle/bottom carbs are not necessarily the same, and the jets aren't either.

 

[Gearhard]

Find carb part number, like
tc119a
tc107a
tc138a

MAIN Jets for a 4 cylinder with two carbs are larger, .092, .094, etc.

Id the carb, then verify the correct jet installed for your altitude.

you can sort through all the carbs, and the corresponding jets per altitude, on
the mercruiser parts dot com web site.

I found the carb #s and have 'TC101A 824 664061-1' top, and 'TC100A 824 589061-2' bottom. There are 14 of the 53 different 125hp for 1989 that match those combinations of carbs. I'll have to pull carbs to verify jet sizes but all '"B" that match those carbs use the same size jets for sea level -1500'. Is this grasping at straws to suspect the jets?

lIs there any type of legend that explains what all the characters in the model numbers mean? My motor did not have any model numbers on it when I got the boat. Apparently the search on the carbs has narrowed the model numbers to 14 and "B" models. Having a legend might help is determining the rest of my model number and make ordering parts easier.

 

[Gearhard]

Can anyone tell me if the larger jet goes in the top or bottom carb? I can disassemble and reassemble easily enough, but need to verify which carb gets which jet, in case they're not right. Thanks!

 

[The Force power]

Fo14191 1 main fuel jet std. .0937 sea level - 1500 ft. (bottom carburetor)
fo18010 1 main fuel jet std. .101 sea level - 1500 ft. (top carburetor)


https://www.mercurymarine.com/en/ca...erm=en&utm_source=Overlay_IP=ca&utm_medium=us

 

[Gearhard]

Fo14191 1 main fuel jet std. .0937 sea level - 1500 ft. (bottom carburetor)
fo18010 1 main fuel jet std. .101 sea level - 1500 ft. (top carburetor)


https://www.mercurymarine.com/en/ca/...&utm_medium=us

Force Power...Thank you for the info and link. That's the best site I've seen for parts breakdown. Actually, I was mistaken on the main jets, was confusing them with the main nozzle. It looks like the jets can be changed without removing the carbs because of size and location. I'll find out when I can get back to the motor. I imagine that they have to be marked somehow to indicate size?

Edit: since it looks as though bowls need to be removed, I will take carbs off for better access. With carbs off I will also soak and clean the carbs.