1995 40HP Force Carb questions

[Rudy H]

1995 40HP Force outboard. Boat is new to me and runs well at idle and low speeds but out on the lake boat will not get above about 3500rpm and boat won't get up on plane. I run the boat at high elevation (4800ft) in Colorado. Thought it was related to prop pitch but have already removed this as being the problem through purchase of significantly lower pitched prop with same result. Currently cleaning carb to remove this as root cause. A couple questions related to the carb:
1 - I don't have a way to measure the current main jet size but it seems like the hole diameter is just slightly less than a 1/16 inch drill bit (.0625) so I'm assuming the main jet is sized for sea level (.062). I plan to purchase a .056 main jet so that it doesn't run so rich at high altitude. Is it possible or even likely that this is the main reason for why I can't reach high rpms?
2 - My service manual refers to a main fuel jet (which I have removed) but then also refers to an "intermediate fuel jet". I can't find an "intermediate fuel jet" either on my carb or in the parts diagrams for my carb. I'm guessing it's a typo in the service manual but just want to be sure I'm not literally missing something on my carb that is causing it to not work correctly. Does anyone know if there truly is an "intermediate fuel jet" on this carb?
3 - I have seen people talking about replacing "reeds" in relation to high elevation. I don't see anything in my service manual or on my carb that is referred to as a "reed". Do I need to find/change my reeds for high elevation or is that something that isn't used on my motor/carb?
4 - My bowl gasket fell apart as I was removing it so I will need to buy a seals kit for my carb. Any recommendations (with part numbers if possible) for which kit is best for rebuilding my carb?
I think that's all my questions for now. Thanks in advance to those willing to share their expertise.

 

[racerone]

Might be running on one cylinder.----Compression test and check for spark on both leads.-----Remote possibility that boat is water logged too.------I am not there to observe some of the facts.----Reed valves are not part of the carburetor .----They are found inside the intake manifold.

 

[Rudy H]

Thanks racerone. I did a compression check when I bought it (110psi both plugs) but the engine wasn't warm so I need to re-do it. Will report findings once I am able to do the test. Read up on reed valves and now realize that they shouldn't have much to do with my power loss. However, with carb off I did look in and could see all the reeds and there didn't appear to be any damage. I see multiple ways to check spark and the owner's manual says to use a spark tester but really don't want to buy one. Is the screw-driver stuck in the boot with the shaft a little ways from the end of the spark plug while turning over the engine the best/safest way to check? Seems like there's lots of strong opinions on how to do it. Also read about jetting for altitude and am becoming more convinced that it could be the root cause of my power problem. Carb was very clean. Cleaned it anyway and am waiting for new gaskets and the smaller jet for 5000+ feet elevation. Is it okay to check compression and spark with the carb removed from the motor? Seems like it shouldn't cause any problems doing it that way... right?

 

[Nordin]

I suggest you to follow racerone.
Check for spark at each cylinder and boat logged of water.

Easiest way to check for spark is to pull the plugs and connect them to the HT wires.
Hold the thread of the plugs to good ground, crank the engine over with the starter and with the ignition ON.

There are cheap spark tester to buy for about 10-15 dollars.

 

[jerryjerry05]

It sounds like your "manual" is a Clymer or Seloc publication???
They're ok for very minor things but don't usually get the important things right.

It sounds like your only running on 1 cyl???
The 40 actually runs pretty good on just one cyl.

The carb: it sounds like your getting WAY to technical and don't need to do anything other than make sure the
main jet is clear (actually at 3500rpm's it sounds like it is).
You only have 1 jet in your carb.At 5000 it should be a .056
The jet should be marked?? Magnifying glass??

Reeds: if the carb is spitting fuel out the front of the carb?? then the reeds might be bad???

Compression: both at 110# the low reading might be the gauge (cheapo, Harbor Freight) or the way it was done?
Cold motor makes no difference.
Both plugs out while doing test?
Carb off is ok.

Spark tester $8

 

[Rudy H]

The manual I’m using is the original service manual for the motor (by Force) so that’s why I was confused. Pretty sure it’s just a typo at this point. Not too concerned about boat being waterlogged due to excellent condition of flooring but I suppose I can weigh it somewhere to be sure. New jet for 5000+ is on its way and I’ll recheck compression and spark and report back. There is gas coming out front of carb when running but it’s not spraying out... more of just a wetness. At this point I’m assuming that the jet being too large may be causing that.

 

[roscoe]

Debbie Downer here: Reality check.

When you get this all running perfectly, you will likely still have issues.

NADA lists that boat at over 900#, plus passengers.
Pushing that kink of weight up on plane with possibly only 27-30 hp, is not going to work.

That rig struggled at sea level when it was new.

Now at altitude.... no way, Prepare to be disappointed and buy more boat and motor, .

 

[jerryjerry05]

I didn't see anywhere he mentioned a make or model of the boat??
Did I miss something?

The jet should have no affect on fuel coming from the carb.
The reeds or the float would cause that.

You can try: remove the carb and turn the motor over as it spins, spray WD or a carb cleaner in the intake.
If it doesn't spray back then the reeds are ok.

 

[roscoe]

Rudy H
Cadet

Force 40HP
January 16th, 2019, 10:52 AM
I have a 40hp Force outboard on a 14ft Bayliner Capri 1401 LS. I use it at high elevation (5000ft). Motor runs well but boat won’t get up on plane.




https://forums.iboats.com/forum/gen...and-topics/10696904-force-40hp-prop-selection

 

[Rudy H]

Yes, the boat and motor should weigh 960 lbs according to the specs at the Bayliner website. Thanks for the easy way to check the reeds. I’ll try that out.

 

[mfkirkland]

delete comment about spinning on hub, missed new prop in original post

 

[Rudy H]

Had the time and equipment to check the things that have been mentioned thus far. 1 - reed check - air is only going into engine while turning over so reeds are working properly.
2 - spark check - both plugs and wires are giving good spark.
3 - compression check - 105 top and 115 bottom.
While putting carb back together it dawned on me that the float "may" have been in upside down when I dismantled it. I say "may" have because I hadn't taken apart a carb before but it seems like I remember it not sitting level when I was taking it apart but now it does sit level. Perhaps a previous owner had it upside down. If it really was upside down then it seems like that would cause flooding, low power at high rpms, and wetness coming from the front of the carb while running. I'm still waiting for my new high altitude jet and carb seals to show up but I'm guessing this things going to run much better when I test it on the water next time if it was both jetted for low altitude as well as having the float upside down. We'll see...

 

[Rudy H]

NOTE: Compression check was on cold engine with carb off and gas disconnected. Seems like warm engine plus gas going into the cylinders would have made a better seal and higher numbers but won't know that for sure until the carb parts show up and I can do a "proper" compression check on a warm engine. Either way, it sounds like anything north of 100 on this engine is still in reasonable range... correct?

 

[Rudy H]

NOTE to NOTE: after reading about compression checks, realized that my compression check reading moved up very slowly and required quite a few engine revolutions before reaching max pressure. I guess I may have ring problems but I'm going to wait until the motor is put all back together and warm before making any assumptions about needing a rebuild. Stinks though...

 

[jerryjerry05]

Comp test can be done on a cold engine and the results will be the same or very close.
Carb off?? no difference.

The first thing I'd do is get a different tester and not a cheapo.
Brand new Harbor Freight testers can read as much as 70# lower than a good gauge.

Did a test on a 2002 225 Mercury I was selling.
The new owner brought a new gauge(HF) and started testing.
#1 cyl 85# #2 85#
I stopped them and said here use my tester.
I bought mine in 87 160$ MAC Tools
Retested #1 150# #2 152# and the rest were the same.

Your poor results will tell you something.
If all cyl. are about the same?? say 100#
Then the motors probably got good comp and the gauge is bad or procedure
was done wrong.
Remove all plugs, throttle all the way open, jump solenoid and let it spin until the
gauge stops going up. Might take 8-9 turns?? Maybe 3??

Bad rings, spray some WD in the cyl and then do the test.
If the results go way up? then the rings might be stuck.

But since your results are all the same??
I'd say the gauge is suspect??

 

[Rudy H]

I guess I'm not too worried that the gauge is wrong. It is a loaner from Autozone. I'll try the WD-40 test. I did everything in your procedure except "jump solenoid". Turned over engine for probably 15-20 cranks, let it rest, and then did that 2 more times before it topped out the reading. I'll need to figure out how to jump the solenoid since that is probably to protect the electronics so they don't build up too much charge that can't be released because the plugs are not in... correct? Hope I didn't already do any damage.

 

[roscoe]

Just trip the kill switch, that will ground out the ignition so there is no spark.

 

[Rudy H]

That’s an easy solution. Hopefully will have time to do test tonight.

 

[Rudy H]

Tripped the kill switch and made sure that there was no spark at the plugs. Plugs out, throttle open, kill switch off, top compression check prior to spraying with WD40 acted just like before... building up really slowly to max pressure. Removed compression meter and sprayed WD40 in thru the plug hole opening, reinstalled compression meter and ran test. Ended up with same result except that it seemed like it was pumping up even slower than before. Not sure what this means... maybe I really do need to get a better compression meter. Thing I'm confused on is what is actually lubricating the rings during this test. I have the carb off and the gas line disconnected from the motor. I thought it was the oil mix in the gas that lubricated the pistons. Aren't I doing damage by turning over the engine so much without any lubrication going into the chamber? I really don't want to be creating additional problems at this point.

 

[kbh121956]

WD40 has lubricant in it. Rent or borrow a good compression gauge.