Force 125 bypass valve

When taking apart my 1986 force 125 the only bolt I snapped was one of the two holding the bypass valve. This motor has seen some salt water and the cavity for the valve, as well as the bottom #4 water jacket, were packed with sediment. I had to dig the valve out in pieces. Can someone explain how this operates and how can I prep it for rebuild. After carefully removing as much sediment as I can manually, I still can't find an orifice in the valve cavity. Is there a solution I can use to clean these areas?

Re: Force 125 bypass valve

They stopped puttin them in cause they were more of a problem than they were worth.
Usually they stick closed.
So all the water goes to the motor.
Now that you've dug out the parts they need to be put back in or make sure the impeller and pump is in good shape.
Your water pump produces way more water than your motor can use.
The relief valve opens under full throttle allowing excess water out the back of the motor.Or through the snout.
Once they stick closed all the water will still go out just the motor doesn't eed the full flow.
If it's stuck open,the motor won't get as much water at slower speeds.

Re: Force 125 bypass valve



When used, there were basically two different systems for the bypass. The only difference was from where the water was bypassed.

Water is delivered to the bottom of the block. Just above entry it passes into the water jacket. Now, in the old style bypass there is a hole drilled from the entry point through to the plastic valve plug. When the thermostat is closed, excessive pressure forces the plastic plug open and water passes down a square cast-in hole that exits right by the exhaust downtube. In the newer system, the drilled hole between the entry and plastic plug is not there. Instead, the water jacket has a separate small chamber at the bottom which is drilled down into the valve chamber. Now, when pressure get high, water will again force open the plastic plug and bypass down by the exhaust tube.

Later engines did not have a bypass at all. The reason: When the water pump pressure gets high, the vanes simply bend and bypass anyway-- that is a characteristic of centrifugal pumps.

Back to your engine---You probably have the newer system. Clean the lower chamber of the water jacket. probe the bottom of the block and open the bypass hole. Then drill out the old bolt and replace. If the block is not too badly thinned there, you may be able to tap oversized, but you should definitely be able to drill and tap deeper.

In the first photo, you can see the separate small chamber above the valve. Note that it is sepated from the rest of the water jacket by an aluminum web. In the second photo, the large hole is the water feed to the block, The smaller hole right next to it is blocked but is a drilled hole up into the separate chamber in the first photo. The bottom is blocked by the match plate gasket when the block is installed. Unfortunately, I did not notice it when I snapped the photo, but the rectangular bypass hole is hidden by the stud in the second photo. This is where the bypass water exits.

The bypass system is not needed and when plugged there will be a hot spot at the bottom of your block, but it should not harm anything. You could remove the valve assembly and fill the hole with epoxy.Then, drill a small hole in the web of the separate chamber so water will circulate through it.

Re: Force 125 bypass valve

Great information guys. Thank you. Frank, I don't find any photos included in your post. Seems it has to do with site maintenance. Hopefully I will find them soon so I might reference what you are talking about. I failed to mention that the spring was badly deformed and the plunger came out in pieces. Given this, would you try to replace these parts or go with the epoxy fill? Do you know of a solution that will break down the sediment? I've been digging around with everything in my tool box but I still can't find a hole in the valve chamber. Thanks for your time and input. I'm sure, as you know, manuals just can't answer every question.

Re: Force 125 bypass valve

On my 86 85hp the hole was far back and to the left (I think). I believe the hole was only 1/4 inch if that. Mine wasnt destroyed like yours so I opted to clean and reinstall it. I started with a flat head and removed all heavy corrosion. A battery terminal brush tool worked awesome for me. The male brush fit in perfectly and I just twisted it until the corrosion was gone. Bend a hanger and prick at the hole and make sure it is clean.