Reeds 1998 75 Force

[TwoFish]

1998 75 Force.

Still looking for the cause of the miss at idle.

Removed the reeds to check their condition and noticed what looks like a small tear in the inner gasket between no.1 and no 2 reed blocks. The close-up photo shows a recessed area in the adaptor plate which looks like it would be part of the original design.

Update

Just tore the gasket in the same area between no 2 &3 and there is a similar recess.

The edges of the original tear look dark as if gasses have been transferring between the two crank cases.

A couple of questions.

1. Do you think this tear could be causing the misfire?

2. The reeds look good to me except a couple do not close completely. (0.5 mm approx) Is this OK?

3. Do I need to remove the reed blocks from the adapter plate to clean up and fit a new gaskets.

4. Do the reed blocks have to go back into the adapter in exactly the same positions and orientation?

5. Do I need to use any thread locking compound on the screws?

6. Is there anything else I should be looking out for whilst I have the motor in this state?

Sorry about all the questions but this is all new to me and I value the advice giving by the people on this forum.

Thanks

TwoFish

 

[pnwboat]

Re: Reeds 1998 75 Force

1. Do you think this tear could be causing the misfire? Don't know for sure, but any torn gasket on the reed assy. should be replaced.

2. The reeds look good to me except a couple do not close completely. (0.5 mm approx) Is this OK? This is not OK. Maximum allowable gap is 0.25 mm. You can try flipping the reed petals over. Might even try bending them down slightly, but not sure I would do that unless it was a last resort. If I were a betting man, I would suspect that this may be the cause for your miss at idle, but don't hold me to that! LOL!

3. Do I need to remove the reed blocks from the adapter plate to clean up and fit a new gaskets. Yes, very easy to do.

4. Do the reed blocks have to go back into the adapter in exactly the same positions and orientation? Not 100% sure about that. I think that they'll go on either way. To be sure mark them before you remove them.

5. Do I need to use any thread locking compound on the screws? Personal preference. I always use thread locking compound on the reed petal screws. Not worth the risk of a screw coming loose and damaging the motor.

6. Is there anything else I should be looking out for whilst I have the motor in this state? I would think about looking for another set of reed petals if flipping them over or bending them helps your problem. I've seen quite a few of the 1995 - 1999 120HP motors that have cracked or broken reed petals. The ones on your 1998 75HP look to be the same design as the 120HP.

 

[TwoFish]

Re: Reeds 1998 75 Force

Thanks for the reply pnwboat.

Just measured the gap at the top of the reed and a couple are larger than 0.5 mm.

I take it that it best to replace all the reeds?

Online I have found them sold as complete reed block assemblies. Around $80.00 to $100.00 dollars a set. Is it possible or advisable to replace just the reed petals in the original blocks?

Thanks

TwoFish

 

[pnwboat]

Re: Reeds 1998 75 Force

This is the only place that I've seen that sells just the reed petals for your specific motor. They're based out of Florida. good price. They have three different types of reeds. Sport, race and drag. These are composite, not metal like the original. I've been using a set of Boyesen composite reeds in my motor. I have over 250 hours on them. I looked at them early this spring and they still look brand new.

http://www.ebay.com/itm/Force-Sport-Outboard-Reed-Reeds-70-90-hp-3-Cyl-1993-up-/280703552780?pt=Boat_Parts_Accessories_Gear&hash=item415b3c4d0c

 

[TwoFish]

Re: Reeds 1998 75 Force

Thanks again pnwboat,

I've contacted the link you supplied and Boysen to get more info.

The price of the reeds on ebay are certainly attractive. Hopefully they are reliable. In any case I have to replace the ones I have now.

The motor has only done 218 hours. I'm a bit disappointed the reeds only lasted that long.

I'll let you know how I get on.

Cheers

TwoFish

 

[kywings]

Re: Reeds 1998 75 Force

We have the same motor and last year you advised me correctly on repairing the fuel enrichment valve. I still have the miss but in Dec I replaced the reeds as a last resort and found the same gap between 1 and 2. I would recommend replacing the gasket and the thread lock on the reed pedals screws unless you buy new reeds. I wish I would of saved the $185 on the reeds and turned them over but I already bought them. After all this work the motor runs smoother, increased rpm by 200 and starts on the first try every time. Still miss at idle and slight high end miss. This fall I intend to go after timing no ideas after that.

 

[RRitt]

Re: Reeds 1998 75 Force

It is worth noting that there is a known issue with reeds in Mercury Force outboards leading to burned out powerheads. The neighborhood Mercury dealer is a family business dating back to 1970's. The lady behind counter says that there was a Mercury shop advisory at one time and that mercury was even replacing entire power heads free of charge back in the late 90's. She said the Force engines backfire when cold and cause mercury composite reeds to break. You can go dig for details but I think the lesson learned is not to run an engine with cracked or weakened reeds. Apparently it leads to catastrophic results.

 

[Jiggz]

Re: Reeds 1998 75 Force

Thanks for the reply pnwboat.

Just measured the gap at the top of the reed and a couple are larger than 0.5 mm.

I take it that it best to replace all the reeds?

Online I have found them sold as complete reed block assemblies. Around $80.00 to $100.00 dollars a set. Is it possible or advisable to replace just the reed petals in the original blocks?

Thanks

TwoFish

I had the same issue with my lower set of reeds being able to see light thru when placed against a light. But only on a couple of the leafs or reeds. I removed the leafs (nothing but screws) play with them a little bit, flipped them over, replaced gaskets problem solved. The leafs or reeds are very sensitive so just a slight push and always look thru light each time. Make sure you use some semi-permanent locktite on the flat-head screws since they don't have lock washers like the tiny screws on the back plate.

 

[TwoFish]

Re: Reeds 1998 75 Force

Thanks for the replies.

kywings. Good to hear your motor is running better. I thought of flipping the reeds but am currently looking at putting in Boyesen reeds. I have heard that these motors may be hard on the composite reeds as the motors have a tendency to sneeze when starting causing the reeds to break. Not sure which way to go on this one. I’m also reluctant to flip the reeds as this will make them bend in the other direction than they were before possibly causing metal fatigue. I think you may be better off in the long run replacing them like you have done.

I’m still chasing the miss as well. I’ll post if I find anything that may help you.

I did find the earth wire from the trigger was corroded at the eye chip where it bolts onto the plate that holds the CDM units. You may want to check yours.



RRitt. Thanks for pointing out the problem with the later Forces. I had read a couple of older posts which gave me the idea to check the reeds.



Jiggs. Thanks again for your input. I always find it helpful.

I’ll make sure I locktite the screws which ever way I go with the reeds

Cheers

TwoFish

 

[Jiggz]

Re: Reeds 1998 75 Force

You're absolutely right, sneezing on these motors seems to be the norm and always happens during cold start with or without the choke.

 

[TwoFish]

Re: Reeds 1998 75 Force

My guess is using a fuel enricher only supplies more fuel to start but leaves the motor running lean from there on until it warms up. A butterfly choke system keeps the fuel mixture richer until the motor warms up and the choke is turned off.

 

[Frank Acampora]

Re: Reeds 1998 75 Force

"Sneezing" on starting is a symptom of a too lean engine. Chokes on these engines were never richening the mixture until the engine warmed-up. They and the newer enrichening valve are push-to-choke and the minute you release the key the engine runs with no choke.

These engines do have an oil recirculation system to mainly improve the idle. It constantly injects excess oil into the combustion chamber or recirculates it to the bearings, depending upon year of engine and design. This keeps a cylinder of the engine from getting a large slug of oil at one time with the resultant loss of ignition or "miss." If this system is malfunctioning, excess oil and fuel can build-up and suddenly enter one cylinder. This will flood and foul the plug for that combustion cycle with the resultant miss

Reeds will not result in a miss but reed problems will result in a degree of loss of power as will a torn gasket---Except if the gasket is torn where it allows puddled fuel in the manifold to be recirculated. At any rate, replace the gasket. Look elsewhere than the reeds for the reason for the miss.

Reeds and Vee blocks are symmetrical and can be replaced in any opening in the manifold reed plate and in any position. Since the reed plate is plastic, use threadlocker compound on the vee block screws as you can not torque them too tightly because of the risk of breaking the plate. If you remove the reeds from the vee blocks, use thread locking compound on the mounting screws or peen the inside of them so they can not work out.

 

[TwoFish]

Re: Reeds 1998 75 Force

Thanks for the explanation Frank.

I find it hard to know where to look when chasing this miss. I find a split gasket and think I've found the problem. It's just as helpful knowing what won't cause a problem at times.

The recirculation check valves on my motor are not working properly. I'm hoping this is the cause of the miss.

It's been difficult to start. Usually needing 3 or more attempts. The setup was correct to the best of my ability. Hoping new reeds will help.

 

[kywings]

Re: Reeds 1998 75 Force

I will tell you that the reeds and gasket will not fix the miss. Mine was hard to start. Once I got it running it almost always died upon acceleration until fully warmed up. Now starts first or second try. Also I can go 2-3 weeks without touching the primer. Still a miss at idle more so when cold. Also a burble or sputter type miss at WOT. I think that causes the motor not to exceed 4800 rpm. I would recommend replacing or turning over all three sets to meet spec. Best thing I have done so far. Very easy as well.