Logo
FULL SITE MENU

1998 25 HP Force running smooth but very slow at full throttle HELP

B

bryniehenry

New member
Hello all, First post. I bought today and took to lake and it starts first pull smooth idle and when i open it up up at full throttle it goes maybe 10 mph. I had a 9.9 that ran faster. My johnson 25 hp that was a 2000 model just recently broke and it ran me 30mph so there can't be that much of a difference. I noticed that a rubber tube with a very small opening had no water coming out under the hood of it but seen it test run with a hose and the water came out under the water level with holes in the shaft is that normal? I am really new to boat motors so have no idea. The motor was cool to the touch after 15 minutes of running so it must be circulating. I also took the hood off and seen that the butterfly opened up all the way and seems that there is plenty of gas squirting in. The choke is off so out of ideas. Please help. Thanks
 
Compression test.
Spark test.
Then go for a ride.
Figure out the RPM's at wide open.
No Tach? Get a Tiny Tach.
I bought one for cheap. Amazon.
If the prop is wrong then it's not letting the motor spin up and your not gonna get the speed.
 
14 ft semi v aluminum. A very light boat trim looks about right
getting ready to head out and try the spark test and pick up a compression check plug do i just pull the rope on the compression test or let it start if it can
 
The compression should be close on all 3.
Pulling the rope to do a comp test is the hard way but can be done.
Try to ground out the plugs so there is no damage to the ecm.

The trim: Set it as straight up anddown or even with the transom.
Then 1 hole out. Then once your up and running you can adjust from there.


Pics can help a bunch so post a bunch.
The transom, the cavitation plate where it's setting compared to the bottom.
Lots o pics??Lots o help!!
 
i did the spark test and found the top cylinder has no fire and the bottom 2 do so now what it looks like the wire goes under the flywheel somewhere
 
it was bought on craigslist so no refund will try to pull the flywheel will it hurt if i run it all year on 2 cylinders till winter. I don't need to go real fast where I'm at
 
The link you gave is that the right part? I could order and then take apart and replace if its really bad and if its a ground or gap then i could have a spare. I would just assume to fix while its apart
 
Before you pull the flywheel.
Go to outboard ignition . com
They have test procedures for your motor.
The 98 used Mercury parts so your stuff can still be found(maybe).
e-bay is a good place to look.
 
After i looked and ran numbers it shows that the part needed is 850899t1 when you read about tho apart it says it is for 5 to 15 hp and i have the 25 so I'm confused if i should buy this or not. it is a hard to find part and they do have one on ebay now so does anyone have any information on this situation before i buy. Thanks for your quick response please.
 
Fishinmotors, Welcome.
You should start your own thread.
Add it to another's and it can get ignored.
Try outboard ignition.com for test procedures.
 
Back
Top