2010 25 toh 4-stroke head gasket help

[steffco]

anyone have a link to the maint manual for a 2010 mfs 25b or could you pm me the head gasket procedure?
Ive been having issues with my oil level and some gray foam on the dipstick as well as an intermittent giant miss and rough running that comes and goes. Did a comp check and got 180, 120 and a funky 170 on the bottom cyl. Im gonna pull the head for a looksee.
local dealers cant look at it for quite a while.

 

[pvanv]

The 25B is EFI... good motor, same as the 30 except for the ECU. I would do a leak down test, looking especially on that low compression middle cylinder. Also make 100% sure the oil is not over full.

 

[steffco]

The 25B is EFI... good motor, same as the 30 except for the ECU. I would do a leak down test, looking especially on that low compression middle cylinder. Also make 100% sure the oil is not over full.

When I put the boat in service this year the oil was overfull and came out the dipstick hole, this had happened before 4ish years ago when I first got it and I thought the original owner had overfilled. I changed the oil and it has slightly increased as for the few hours Ive run it since but it has a white foam on the stick as well. oil does not smell like gas. The plugs all looked the same and the miss comes and goes.
how could a leakdown test help me since I have discolored oil and funky compression. I was hoping for something simple like fuel cooler or blocked breather but I don't think that would effect compression?
Id hate to keep running it and mess up a big ticket item.
Thanks for you input

 

[steffco]

When I put the boat in service this year the oil was overfull and came out the dipstick hole, this had happened before 4ish years ago when I first got it and I thought the original owner had overfilled. I changed the oil and it has slightly increased as for the few hours Ive run it since but it has a white foam on the stick as well. oil does not smell like gas. The plugs all looked the same and the miss comes and goes.
how could a leakdown test help me since I have discolored oil and funky compression. I was hoping for something simple like fuel cooler or blocked breather but I don't think that would effect compression?
Id hate to keep running it and mess up a big ticket item.
Thanks for you input

This is a fresh water engine on a pontoon that mostly goes low speed and sees maybe 50 hrs use a season. perhaps there is a ring seating issue but would that cause oil level increase and foam in oil?

 

[MattFL]

The leakdown could potentially help you verify a head gasket issue before taking it apart (or other leak into the cooling passage issue). When you apply the air to the trouble cylinder, you could remove the thermostat and listen for air leaking into the cooling passages. Compare to what you hear from the other cylinders. To confirm there is water in the oil, you can draw some out into a container and let it settle for a day or two. The water will separate.

 

[ahicks]

My experience with the Honda's run on pontoon boats - rarely much over an idle - is the thermostats need to keep the engine warm enough to burn off the carbon build up that occurs around the piston rings, especially the bottom one.

I have pulled engines with no thermostat and 80-90 psi down, cleaned the pistons and rings (un-sticking them), and using no other parts, just gaskets and a new thermostat, restored compression to 125-130 psi.

The engines must run warm enough to stay healthy!

 

[steffco]

Did my comp checks again and cold they are 120 on all three cyl.
After running for 15 min on the muffs they are 190,120 and 150.
What can cause comp to go up? maybe sticking/carboned up exhaust valve? the plugs all look good and the motor sounded fine while running on the muffs.
The dipstick has small amount of grey foam on the top above the normal fill level but the oil itself looks great, I just changed it and the filter and have run it 2 hours since.

 

[steffco]

after some research I found comp is supposed to be 164.
I had 120ish on all three then i sprayed in some oil and got 150-160 on all three. Im thinking I got stuck rings, Plan is to add seafoam to fuel and soak top end with intake spray cleaner and then run it hard for a bit to see if there is any changes. If no change Ill check valve adjustments.
I was wondering if I tilt the motor up if I could add seafoam(ATF) through the spark plug holes and let it soak overnight?

 

[pvanv]

Seafoam is basically mineral spirits. Never had any luck with it. Your mileage may vary. Possible the rings aren't fully seated if it's never been run really hard and hot. I have checked valves on tons of these, but never found one that needed adjustment. A decarbonizing spray session won't hurt.