2000 johnson 25 j25tessd overheating and SLOW at WOT

[Kloctower]

Outboard overheats goes into interrupted ignition phase (SLOW mode) to protect itself. Happens only at WOT once it's warm it surges up and down in rpms. Head gets too hot. Last owner changed head gasket. Could be in wrong??? Engine runs fine low idle maybe a little cough or sneeze now and then at idle but it overheats eventually. I used sea foam then ran into mud one day then this began.
All repairs listed happened this weekend I been busy and I'm frustrated.
New water pump, water tube good, tell tale OK
New power pack
2 new coils
New thermostat, spring, o ring, cover gasket
New fuel line to tank and both connectors
New fuel and oil mix , new line to motor inside cowling
Fuel pump rebuilt
Carb. Rebuilt
Blew air through tell tale which did make the exhaust relief spray out water with exhaust. It has not done that before until after the air.
The motor had no thermostat when I opened it up. It runs hotter now that I put the thermostat in. Made the problem worse.
I'm sure you hear this a lot but I am a worthy mechanic. Just not an outboard mechanic. I work in the automotive manufacturing industry. On robots and electronic or pneumatic or hydraulic equipment. Small engines and automotive tech. my college major (failed English)

My next course of action is to take the head out and check that then the exhaust gaskets next. I'm thinking I have water jackets blocked inside the motor somewhere.

 

[Kloctower]

12 views with 0 responses I'm getting scared

 

[Kloctower]

I just pulled the head cover and the head itself off. The water jackets look clear of any obstructions except for the top and bottom there are rubber plugs that look Factory the one on the bottom is degrading and a gentle touch with my pic rendered parts and pieces to be useless which fell out. I wish I could upload the pictures but my phone won't take a small enough image from me to upload it to the site it keeps rejecting the upload for being too too large. The head gasket does look like maybe maybe some water was getting past but the cylinders and the spark plugs did not show any signs of water in the cylinders I'm really at a loss here should I go for the exhaust gaskets? Or am I just an idiot that overlooked a simple fuel starvation problem that was causing my motor to overheat? Someone please help me even if I wanted to take my boat to a mechanic no one can work on it for a month because of winterizing and it's my duck boat motor so I need it now it's duck season

 

[Kloctower]

Well could one of you guys direct me to someone or some forum better suited to answer my problems please? I was told this is the best forum for this kind of problem. Buddy said there are many good outboard mechanics on here and this forum is the fastest one to use... am I doing something wrong here or is this just out of the wheel house for the guys on this forum? How can I make my thread better for the diagnosis? I mean I know people are busy but thirty plus views and no one has a clue? How can I upload pics?

 

[racerone]

Those rubber plugs guide cooling water around the block.------Install new ones.------------Do I have a clue ?-------Well I own more than a dozen of those motors I think.---Rebuilt some already.

 

[Kloctower]

I'm new to this forum I didn't mean it like that what I meant was if there is a better area to post my questions I would like to put them there because I've had 30 people read my story and zero replies except yours. I have good water flow the rubber grommet is in good shape I'm getting good water up to the motor and through the thermostat it was shooting out of The Telltale hole about eight feet when I took the tube off but it's not hot it's cold water even though it's coming out of the exhaust side. Is there supposed to be 2 or 3 of those rubber plugs inside the water jacket? Because I have one on the top and one on the bottom right that is corroded and damaged. I did not mean to offend you or anyone else I just felt like I was not drawing enough attention so maybe my post was in the wrong area

 

[racerone]

The parts book shows 3 deflectors ( rubber tubes ) in the block.-----`Water coming out the tell tale indicates that the water pump is working.-----------This absolutely does not mean that the motor is cooling properly !!------------A very , very common but mistaken belief of many novice outboard owners.

 

[Kloctower]

Thank you for your time and replys!!

The parts book shows 3 deflectors ( rubber tubes ) in the block.-----`Water coming out the tell tale indicates that the water pump is working.-----------This absolutely does not mean that the motor is cooling properly !!------------A very , very common but mistaken belief of many novice outboard owners.

I am very aware the that the tell tale working does not mean it is cooling. Just stating the facts to get to the point. The water is cold I just wanted the reader to know this. I understand the water is not getting to the right places for some reason. At least that's what I think. I'm thinking the exhaust gaskets are shot. I'm no marine mechanic but definitely not a novice either. I own six Johnson outboard motors and do all maintenance myself. Just not trained and feel uncomfortable inside these power heads without guidance.

 

[boobie]

If you put new water deflectors in the block make sure you have them in the right places. Service manual shows where they go..

 

[Kloctower]

Thank you guys for the help.
I am going to replace them all. I see the places in the manual plus there are tabs in the casting to hold them in place that's how I knew one was missing. I think the missing one is somewhere else in the block in pieces this causing my problem

 

[jakedaawg]

I would be removing the lower and back flushing through jackets while head is off and then through thermostat cover once assembled till I was sure there are no more bits of old diverters or mud in there.

 

[Kloctower]

Yes sir I agree. That is worth the extra effort

 

[Kloctower]

So I removed the exhaust cover and there is nothing out of place. No obstruction. Starting to get worried here. What else can it be? Timing off? Stator problem? Pinched water tube or bad grommet? Something stuck in the water jackets at the bottom of the block? Exhaust housing looks normal. Could this be caused by a warped head?

 

[jakedaawg]

Did you back flushed and retry? Did you replace e diverter and install correctly?

 

[Kloctower]

No I'm waiting for parts to get here. No local parts available. Got all The surfaces ready to go back together with fresh gaskets. I'm planning on dropping the lower again tomorrow morning and trying to shoot some water up the water tube. Anything else to look for ?

 

[jakedaawg]

If you had a missing/moved diverter, that could explain your overheat.

Shoot the water in the power head and out the water tube with lower removed. In through stat assembly opening works well but it must have the heads on and diverter in place and lower removed.

 

[Kloctower]

Did you back flushed and retry? Did you replace e diverter and install correctly?

Install diverters correctly? Just want to make sure don't miss what your getting at. Thanks

 

[jakedaawg]

In the.proper place, and seated correct depth. Flush with deck

 

[Kloctower]

Quick question on the powerhead what gaskets get a sealing compound like 3M 847 and what ones go on dry? I know that the head gasket does not get any of the 3M 847 what about the water jacket in the exhaust gaskets?

 

[Kloctower]

Could this problem be caused by the stator? Or the timing being off? As I dig deeper and deeper into this outboard I continue to find no problems. I'm starting to think maybe it was electrical all along.