? about force 120 on 20 foot trophy

[kobe24]

I recently bought a 1998 trophy 2002 FF W/A with a force 120 outboard. I took it out for the first time on sunday and found that i could only hit 21mph at WOT 4,000 rpm and cruise at 18mph and 3,500 rpm. I cant get anywhere near the 5,250 max rpm.

Im thinking somethings not write. At that speed its going to take me almost an hour to get to my fishing hole 15.2 miles from the marina on flat seas :facepalm:. The question is do i have to live with that until i re-power with a 175 optimax in a few years. Or is something not rite.

I have good compression on all cylinders and the motor sounds fine at speed. Could it be a prop isue. the only numbers i can find on the prop are ( 4a or 4r - 77344 - c1 - 17 )...

 

[chrome dome]

Re: ? about force 120 on 20 foot trophy

motor seems a little on the small size for that size boat,
but you're right, somethings not quite rite with those RPMs,
at a guess, l'll bet it's a fuel delivery problem, carbs/fuel pump may need cleaning or rebuiding

 

[Frank Acampora]

Re: ? about force 120 on 20 foot trophy



You are correct: Something is not right.

This 21 foot cuddy with a 1989 Force 125 reached between 33 and 35 MPH --probably at about 5000--with a 17 pitch prop.

Your newer force with a Mercury ignition and Mercury lower unit should easily be able to match that.

First re-check compression on all cylinders. Good compression should be up around 140-145. Check that carbs are opening fully, check that there is no fuel delivery problems, and check that all cylinders are getting a good spark.

Read and follow the FAQs Sticky: Synchronizing carbs and timing. It was written for older Force engines but yours will be very similar.

 

[roscoe]

Re: ? about force 120 on 20 foot trophy

I recently bought a 1998 trophy 2002 FF W/A with a force 120 outboard. I took it out for the first time on sunday and found that i could only hit 21mph at WOT 4,000 rpm and cruise at 18mph and 3,500 rpm. I cant get anywhere near the 5,250 max rpm.

Im thinking somethings not write. At that speed its going to take me almost an hour to get to my fishing hole 15.2 miles from the marina on flat seas :facepalm:. The question is do i have to live with that until i re-power with a 175 optimax in a few years. Or is something not rite.

I have good compression on all cylinders and the motor sounds fine at speed. Could it be a prop isue. the only numbers i can find on the prop are ( 4a or 4r - 77344 - c1 - 17 )...

Hate to be the one to say it, but hopefully it will help others that read this.

You really should have taken it out for a sea trial before you bought it.

Yes, something is not right. You should be getting more rpm and speed.

# on prop likely are 48-77344-xx17

That is a Mercury prop, diameter measuring 13.25", 17pitch

 

[jerryjerry05]

Re: ? about force 120 on 20 foot trophy

What's good compression?
Test the spark?

 

[kobe24]

Re: ? about force 120 on 20 foot trophy

The last time i had the compression checked it was between 118 - 127 psi. It had the fuel pump diaphragm replaced in 2010. But im not sure about the carbs. They where last serviced in 2010.

Yea i know i should have had a sea trial but i didn't own a tow vehicle at the time. ether did the guy i bought it from. I had to settle for a barrel test:facepalm:.

I had a mobile marine mechanic come with me to go thru the motor before i bought it and the mechanic said all was well and gave me the green light. i guess i wasted $150 bucks on a bum mechanic.

I only paid 5,000 for it, well actually 2,500 i have a partner. so is it worth fixing or should i sell it. The boat it self is in realy good shape. I was hurt at work a while back and have a bad shoulder so i cant really work on it my self at this point in time. I would have to take it in. thanks again for the help.

 

[Frank Acampora]

Re: ? about force 120 on 20 foot trophy

Well, you are taking the owner's word for facts. If you did not own the boat in 2010, then it is time to replace the fuel pump parts--very easy if it is the old type Force pump OR the newer Square Mercury pump--and cheap too. Compression is a little low, but if it is equal across all four cylinders, it may just be that specific gauge. Re-check it anyway. You can also check the carbs yourself. Simply follow the sync sticky in the FAQs at the top of the forum.

Even if you have never worked on an outboard, you can not fail. You will get all the help you need here (except physical labor).

 

[kobe24]

Re: ? about force 120 on 20 foot trophy

I didnt just take the owners word for it. Im not stupid..lol . I have the records for all service done. I even verified it with the prev owners mecanic.

But im pritty shure i just found the prob. the plug wire on cyl 3 was disconnected:facepalm:LMAO. I'll take it out again next weekend and report back. Thanks again for all the help guys. I really apreceate it.

P.s - Do you think some ring free or sea foam would help with the low compression. Or would i need to have the cylinders honed and new rings installed?

 

[roscoe]

Re: ? about force 120 on 20 foot trophy

Plug wire would do it.

Ring Free or Seafoam added to gas will help to maintain the fuel system.

A thorough decarb of the engine with SeaFoam will help to clean her out, and may increase compression. Can't hurt to try.

There are detailed instructions in the FAQ forum.



They combined 2 decarb methods into one thread, here:
http://forums.iboats.com/engine-frequently-asked-questions-faq/decarbing-faq-158076.html

 

[jerryjerry05]

Re: ? about force 120 on 20 foot trophy

The comp should be around 150#.The top and bottom cylinder a bit lower than the others.
For some reason it was designed that way.
If the pistons are low in comp, are carboned enough to need a Seafoam treatment it might need new rings or cylinders bored???????
Ge a good tester and post the #s
The oil used in the gas shouldn't allow the deposits/carbon to build up.
They do if the motor's not set up right. The carbs out of adjustment, the fuel recirc system clogged.
Timing off??
Make sure the comp is good and the systems are set right and it should last a long time.

Have twin 88/85's new they carboned up fast. Then they introduced the newer TCW-2 then TCW-3
After that not 1 problem with carbon. But mine are always tinkered with and I know they are set up right.

 

[Jiggz]

Re: ? about force 120 on 20 foot trophy

That's a good find on the disconnected plug wire. Do a sea test again and report back. If it hits 5000 RPM you should be good to go.