Issue: My 1987 Force 125 won't idle with the cowling on
Issue: My 1987 Force 125 won't idle with the cowling on when its in the lake...(of course it works fine on the muffs)...
Description: My Force 125 is acting up this summer...I can start it up fine...but after about 1-5 minutes of idle it chokes out. If you remove the engine cowling you can see some exhaust you can't really tell where it was coming from. If you get it in gear before it dies you can run no problem. Only issue is I eventually need to dock it and nothing sucks worse than rough lake water and a dead motor around 10 other boats. Plus it gets harder and harder to start too after you start snuffing it out. Sound familiar? I've seen about 10 posts like this...we'll my turn...and I'm going to show you what I'm doing to fix it. (Hopefully...)
I checked the basics like the rubber boot on the water jet thing...and the donut seal near the bottom on day 1. Muffs worked fine...launched it and it snuffed out after about 3-5 minutes of idle. I recently changed out the lower unit and was concerned that possibly that was the issue b/c it worked fine last season...but its not the lower unit I'm convinced...I think I just finally have to "pay the piper" on this one....
As it stands...I'm about 51% done with what I think will be the repair and wanted to solve a few mysteries along the way.
The photo 64.jpg attached shows the view down the motor leg where the exhaust snout fits. You can see 2 drain tubes on the top and the water line that comes up from the impeller on the bottom of the screen. I mention this photo b/c when I examined my idle rubber boot/spring thing...it had one of the drain tubes jammed in it. I didn't know any better so I put it all back together like I found it. I hear a lot of guys on the board say ...there was this tube thing in my spring...I didn't know what it was until I took the motor off the leg and realized ...it had washed out of its proper place and was trying to be flushed out by the engine . I took some marine grade 5200 RTV and glued them both back in place.
Nearly done scraping off the old RTV...
The next photo shows the bottom of the motor...You can see where the exhaust snout/leg fits on. What I say is I'm pretty sure that I was leaking exhaust between the exhaust snout and the shift lever area "somehow." Exhaust was killing the idle...I knew that for sure...but where? I sooooo just wanted to patch a leak with a little J B Weld and call it done. Considered cutting 2 four inch holes in the cowling...anything but this...
Anyway...after dismantling...I'm pretty sure the gasket area wasn't 100% intact all over the "important places" inside the motor...few areas with some water type scale/calcium surely were leaking (if I had to guess from the result...) I couldn't see smoke pouring out...but it was enough to snuff the motor after a few minutes..kind of like a fog when you took the cover off. I notcied that the exhaust snout leg gasket was intact...but probably not making great contact b/c it was all covered in scale/calcium type gunk. Surely not a air tight seal. What you should realize too is that the water tube coming up from the impeller is not air tight...so surely exhaust can come up that tiny hole around the tube. Which makes me think that if you get a good seal around the exhaust section...you're golden. If you don't then its going to be leaking out the shift lever etc...
As I do this I'm a bit concerned to see if I can get a good water tight connection between the impeller water tube and the bottom of the motor after I install new gaskets and RTV...it will change the distance between the previous incoming water tube height and the bottom of the motor. I may try and push the water tube up 1/4 of an inch and then let the motor weight push it back down the right distance.
Anyway...hope I have the patience to let the RTV fully cure before I crank it up and hopefully this is the ticket. So far its not too bad...but it is surely a job you don't want to do twice. I'll think about that before I turn the key too early...
Re: Issue: My 1987 Force 125 won't idle with the cowling on
The gasket and hole around the water tube make no difference because at idle they are under water.
The white plastic tubes serve to keep the top of the leg filled with water while running. This keeps the exhaust down tube cooler and also cools the midleg so it does not radiate heat to the rear cowl cover. Second photo: Notice the rectangular opening at the rear of the match plate? This is where used cooling water exits into the leg. When the water level rises, some exits the idle relief holes in the back of the shroud and some exits through the exhaust. The real purpose of the two holes in the rear shroud is to relieve exhaust back pressure when the engine is sitting low in the water--like at idle. At that point exhaust will preferentially exit these holes instead of backing up into the engine exhaust ports. Thus, idle is improved.
I see you have broken at least one bolt on the exhaust down tube. That's a fun job to fix! No gasket is used on the down tube to match plate and no gasket is used on the match plate to leg. A thin coating of silicne RTV is used at the match plate surface. Do not use too much as you can see a water passage around the perimeter of the match plate. You do not want to clog this groove.
Re: Issue: My 1987 Force 125 won't idle with the cowling on
Thanks for the suggestions...I've learned a lot from this board and your information was very helpful.
The broken bolt was fun to drill and replace for sure. Lost another near the top rim of the leg cover (no big deal - left it out). I didn't catch your comment about the groove/water passage until after I put it all back together... But think I did a pretty good job making sure I didn't over do it with the RTV near that section. I am sure that passage was totally plugged solid w/ RTV when I disassembled my motor which was surely not a good thing and its better now.
After I got all the parts back together it was hard to wait the 24 hrs for the RTV to cure before I fired it up to test it out...but I waited.....
The outcome? Its freaking working! Yea! Which is a relief making the time and effort worth it. The idle is sold with the cover on or off and the more idle throttle you give it the harder it runs...vs before it would ramp up a bit but then because of more exhaust in the cover it would pretty much snuff it out and not want to restart... Now I can idle away a full tank gas.
It will occasionally conk out during docking maneuvers fwd/idle/rev sessions....but immediately restarts and runs fine. Thinking I need to tweak the idle speed/idle fuel mixture a bit. (Time to read up on this...) Then again its probably always done that . Maybe fuel pump or carb work? Not sure how to tell when its time to service these guys vs. just swapping parts (aka throwing money at the problem vs. fixing it).
Bonus - Found my replacement "used" lower unit is full of "milky" oil....I've barely had it in the water for more than an hour actual running time since I got it done. (I did have the boat in the slip for 3 days.) The guy is going to pressure test and replace the seal(s) for me. I changed the lower unit oil and will run it an hour or two to test out my exhaust job before I send it off for a replacement seal(s).
Here are the things I learned doing this job I'd wish someone told me before I started...
1) All in all...you only need a few socket sizes...4-6 total. But I'd say you need a about every socket and universal joint extension known to mankind...in all 3 sizes (1/8, 1/4 and 1/2) and you're good to go. Bring 'em all to the site. Use hex wrenches/sockets if you can vs. 12 pt b/c if you strip one of these guys at the torques you may be using to get loose..you're going to wishing you didn't.
2) I used the "freeze" spray penetrating oil which successfully got the main motor bolts off without breaking them. (I was pretty worried b/c they looked pretty nasty...rusty etc). I liked the price $5 for the can of freeze stuff since I don't own a torch.
3) The surprise was needing a "crow foot wrenches" to get 2 really really awkward bolts off on both sides where the shift level comes up. Its a 14mm size. I just couldn't get the torque on my small "open ended" wrenches and I'm a pretty strong guy. Socket won't fit etc. That was a bear to get loose and would consider it the make/break moment of the repair...if those don't come out...you're done for. I didn't want to take off the intake etc but you could go after it that way making more room or possibly making it worse if the intake bolts break off.
4) Don't RTV shut the water passage near the exhaust as Frank pointed out.
5) Get the exhaust snout gasket ahead of time...got mine on ebay...new old stock...$5 + free shipping. Cheapo.
6) Takes about 85% of 1 tube of the black RTV...oil resistant kind is what I used...like <$8.
7) You can man handle the engine off the motor mount after you remove all the bolts...I'd say its about 120 lbs more or less guessing. I thought I might need an engine hoist etc...I leaned it on the side away from the fuel filter across the base of the motor cowling...while I clean the gaskets etc...But I prefer 2 people to remount it b/c you have to get the gear shifter up the hole etc and keep wires out of the way etc.
8) Be afraid of the little bolts...those were the ones that twisted off on me. If it doesn't give with reasonable effort...consider how much you need to take it off before you "go for it". i.e. I probably could have left the motor exhaust snout on but I redid the RTV there too breaking off a small bolt...rather than trust it was "good enough".
9) See #8 - Give up on screw extractors if you already twisted off the bolt...just drill it out possibly under size if you are near the edge of the material and call it day. The extractors break off and are MUCH harder to drill them out too than just softer bolt steel. The #1 cost of this job was cobalt drill bits to fix a mistake...drilling out the broken extractor. I think I literally blew 50 bucks on about 8 of the little buggers...plus the screw extractors which broke. All for 2 little broken bolts. Ugh and the time...wasted.
10) Save your receipts...I over bought a few things like drill bits,replacement nuts in the event the originals stripped out on me and extra RTV...returned $25 in materials I didn't end up needing. If I was bit more organized I'd have not spent 30 minutes tracking them down after the job was done.
The whole job cost 1 tube of RTV, lots of time and leveraged my existing tools and is in the realm of the hack mechanic assuming it all stays together . My situation added in $50 for the drill bits and extractors for the two bolts that snapped off which hopefully you can avoid.