Johnson 88 SPL water blockage?

[RoGun_Mako171]

After replacing the head gasket on the port side, I noticed cylinder 2 and 4 becoming very hot within 2 minutes or so while connected to muffs, while 1 and 3 were very cool to touch. I could keep my hand on the 2 or 4 cylinder for 5-7 seconds, so somewhere in the 130-140 degree range. Thinking I had a bad thermostat, I did a thermostat service and no corrosion (engine is only used in non-salt water) and both thermostats operate the same, so I put it back together, swapping the thermostats and found the same results.

After doing some research, I decided to run it for a bit with the hoses from the heads to the thermostat housing disconnected and (thankfully) no more heating of the port side! Very happy to rule out water getting into the heads from my head gasket replacement. So now I'm thinking I must have a blockage somewhere, but I'm not sure where. Some additional info is that the port side idle relief does not spray water when running on muffs, but the starboard side does. And the drain hole on the port side of the lower unit does not have the same water pressure as the starboard side.

Any ideas where I should start looking for the blockage?

 

[oldboat1]

Possibly T.stat bypass blocked?

Fresh impeller? Test in a drum or the lake, water depth a few inches above pump. (Can't really test on muffs -- hose pressure does the work.)

 

[RoGun_Mako171]

The thermostat bypass looked fine when I pulled apart the housing and serviced. The impeller is old and does need to be replaced. I will test it on the lake tomorrow or barrel tonight and will report back. Thanks!

 

[oldboat1]

Just to be clear, muffs will cover for a weak or failing fuel pump. Best to replace the impeller, and go from there -- don't want to overheat or bust up an old impeller (or both).

 

[F_R]

The thermostat bypass looked fine when I pulled apart the housing and serviced. The impeller is old and does need to be replaced. I will test it on the lake tomorrow or barrel tonight and will report back. Thanks!

I'm glad to see you say that, because I was about to. You cannot test a water pump while running on muffs. Get it in the lake and see what you have.

 

[RoGun_Mako171]

I tested in a barrel with the same results. Strong spray from the overboard water indicator, port side block heated up to the hot range in a couple of minutes. I will be ordering a water pump repair kit to get that out of the way. Looking past the water pump, what else should I expect to take apart next? I want to order the gaskets, etc. for the next option when I order the water pump kit. Also, the trim tab screw is in there very tight and I was wondering if PB Blaster or heat would be the best option to help get it free? Don't want to break anything.

 

[oldboat1]

Didn't mean to refer to the fuel pump earlier, obviously -- water pump. But now that you raise an open question, if the motor is new to you carb or fuel pump service is often on the agenda. But not necessarily. Don't fix it if... you know.

If you don't have one, an open air spark tester is essential for troubleshooting, and an IR gun too (both cheap, if you need to get them).

 

[RoGun_Mako171]

Thanks for the input. Have owned the boat a year and have been doing a lot of learning with it, it's my first boat. When I was asking about looking past the water pump, I was more referring to where the potential water blockage may be if fixing the water pump does not resolve my issue with the port side cylinders heating up, but does not heat up when the hoses from the cylinder head to the thermostat housing is disconnected.

I have to admit that I don't understand how the water flows on the engine. How does it get from the thermostat housing to the exhaust and the idle relief ports?

 

[oldboat1]

With a saltwater motor, the water passages become corroded -- can also happen if running in silty water. Solution is to pull off the head covers and clean out the passages. If you didn't find corrosion around the t.stats, passages are probably clean.

Got a compression tester? Can always borrow one from an auto parts store -- good to have baseline numbers.

(Can't answer the water flow question on yours without a chart -- may need FR for that.)

 

[RoGun_Mako171]

Yes, the compression in the cylinders is #1=110psi, #2=105psi, #3=110psi and #4=105psi after replacing the head gasket on the port side. Had the head cover off and replaced the head cover gasket on the port side, all passages are clear.

 

[oldboat1]

Manual for reference here, maybe: http://162.144.28.33/lib/library.html

 

[interalian]

Thanks for the input. Have owned the boat a year and have been doing a lot of learning with it, it's my first boat. When I was asking about looking past the water pump, I was more referring to where the potential water blockage may be if fixing the water pump does not resolve my issue with the port side cylinders heating up, but does not heat up when the hoses from the cylinder head to the thermostat housing is disconnected.

I have to admit that I don't understand how the water flows on the engine. How does it get from the thermostat housing to the exhaust and the idle relief ports?

Once the water passes the thermosats, it's just dumped down the outside of the exhaust horn for cooling.

 

[RoGun_Mako171]

Ok, so I guess I will need to pull the power head too to see if there is something blocking the water from the port side thermostat. I did pull the power head once for a nasty leak of black ooze down the outside of the midsection that resulted from the air silencer base return hose being clogged/deteriorated. It made a huge mess of everything where the power head and midsection meet. Perhaps a missed something when I cleaned that up. While I have the power head and lower unit removed for the water pump maintenance, I will have access to the exhaust housing to clean that up too and replace the gaskets.

As for removing the lower unit, the trim tab screw is in there very tight and I was wondering if PB Blaster or heat would be the best option to help get it free? I have a history of just using my breaker bar and have broken more than one thing in using it. Don't want to go there.

 

[interalian]

The back side of the thermostat plate is a common cavity for both sides to flow out. I don't think you have a problem there.

If the tiny relief hole in the thermostat plate is blocked, no water will pass the thermostat and it will stay cold, and therefore closed. This changes at high throttle as the water pressure will overcome the spring tension on the poppet and allow water to pass. I would take the thermostat plate off again and check the two small holes are clear. Consider enlarging them slightly as well - not too much though. Benefit to enlarging them is they are less likely to clog. Con is that they flow too much water and can make the motor run too cold.

 

[interalian]

[No message]

 

[Rustywrench]

I don't see where you mentioned why you replaced the port head gasket? If you look at the picture that was provided you will see the middle water diverter. It must be in position so it doesn't block wayer flow. After time passes or a motor has been hot the hose collapses & moves out of place against the block. This will impede the water flow. Just a possibility. You can order new water diverters.

 

[RoGun_Mako171]

Ok, I will check out the thermostat plate holes and make sure they are clear. Thank you interalian!

 

[RoGun_Mako171]

Thanks for the input RustyWrench. I replaced the head gasket because of low compression (100psi in each port side cylinder, while 110psi in starboard side) and had a theory it contributed to excessive white smoke, which I think was wrong because I did not have water in the cylinders. I regained 5 psi in each port side cylinder after the head gasket replacement. And I did make sure the water diverters were in their proper place.

 

[RoGun_Mako171]

I have the thermostat housing apart again and find there is only one hole in the thermostat valve body, but the hole lines up with the center divider in the thermostat cover which seems like it would render it useless. When I look up the part on crowleymarine, the diagram shows it has two holes that would line up with each thermostat chamber in the cover. But the picture of the part only shows one hole in the middle, the same as I see on my boat. I'm trying to upload .jpg pictures, but am getting "unknown error", which is sad because pictures really help explain. I'm just question why the starboard side works if the divider is covering that hole.

I'm thinking of busting out my drill and making a hole in the valve plate so the water can pass through on the port side. Any thoughts on that?

 

[interalian]

From memory (it's been a while), the bleed holes are inside an oval slot. They're only about 1/16" diameter. The slot is supposed to straddle the divider in the thermostat cover. The motor side of the assembly is one large opening. Assembly of the thermostats is not intuitive. A photo would definitely help.

Photos to this site can only be 400kB max. Try re-sizing.