2005 f115 runs rich surging no apparent loss of power.

[mahtzo22]

I have a 2005 f115. 804 hours. in march? it developed a miss at the end of the day. Water in cylinder. Head gasket leaking/blown. new head gasket. motor back together and it seemed fine. Initial sea trial 5.6k rpm wot and 30kts which is slightly better than it did before head gasket. Ran it to one of the local Islands and noticed what seemed like an intermittent miss in harbor at end of day at 1.4k rpms. #1 Plug fouled and smelled rich. On hose it seemed to run fine. switched injectors because I/we suspected a problem with injector. the same issue (intermittent miss/rough at 1.4k rpm) but performance fine at high rpm (wot 5.6k rpm and 30knts). Same plug fouled and running rich (could easily smell on boat when running). Put on hose today and it doesn't appear to miss at 1.4k but it surges noticeably beginning at approx 1.4k and continues to do so up to 2.2k rpm. (didn't run higher than that on hose).

While I am fairly mechanically inclined, I don't claim to be a knowledgeable or good mechanic. I can follow procedures. I was hoping that someone here could point me in the right direction.

I have yds but don't really know what to look for. Still figuring out how to use the basics of the program.

[TownsendsFJR1300]

I'd try new plugs to start with.. It's possible #1 plug is bad...

[mahtzo22]

Thanks, I forgot to mention that I tried that.
put a complete new set in when I switched the injectors.

it may or may not be relevant...two days ago at end of day (was running on hose), the #1 plug was cold while others were warm. put a new plug in and ran again yesterday and all plugs warm.

[99yam40]

which cylinder was getting water in it before changing the head gasket?
if it was #1 then there is a chance it is still getting some in there and fouling the plug keeping it from burning fuel properly

have you checked for spark on #1 with a spark tester?
if there shows to be spark voltage there but the plug is not jumping the spark to burn the fuel , then that cylinder and spark plug will be cooler than the others

[mahtzo22]

Thanks
#4 cylinder had water.
I checked the #1 with a spark tester using yds. I set the gap at 7/16 initially and increased to 5/8' with good spark. (daylight had trouble seeing spark but could hear it snap pretty clearly).

edit: also checked #2 with spark tester for comparison. they seemed to both be sparking the same.

[mahtzo22]

A guy that saw me working on it yesterday suggested it could be water in fuel. could that have that effect on only one cylinder? I would guess that water in fuel would not be localized to one cyl. Also, would water in fuel cause it to run rich? Possibly mess with a sensor? I suppose I don't know for a fact that the only issue is with cyl #1...just assumed it to be the issue because the other plugs all seemed normal.

[mahtzo22]

I also even checked valve clearance because I found some info on line regarding honda engines with valve clearances too tight (exhaust) leading to misfires. thought perhaps it could apply to Yammys. There were a few (4) that were slightly out of spec (1 intake .010" and the others exhaust .015, .016, .015). I ordered new pucks but they have not yet arrived. I don't expect that it would make a difference because the issues with the honda's appeared to be for clearances that were too tight.

Also, forgot to mention that I had the injectors cleaned as preventative maintenance at the same time that I changed the head gasket.

[TownsendsFJR1300]

If there's any doubt about the fuel, get a small aux tank and fill it with fresh fuel...

I would also drain the VST and catch what comes out specifically looking for water.

You are correct about the valves.. Valves too tight will cause misfires, overheating of the valve(not enough "seat time"). Being somewhat loose shouldn't cause your issues, it'd still run, just not 100%

Lastly, not mentioned was any type of compression / leak down test.. I would do a "leakdown" test on all cylinders. It's possible damage occurred with the blown head gasket.. Very loose valves (they tend to tighten with use) could be an indicator of damage to the valves.

I gather the valve timing belt alignment was re-checked after assembly..

[mahtzo22]

Thanks Scott! I appreciate your help. (and you too 99yam40.
I have done a leakdown test. It checked out fine. Didn't do a compression test but I gather the leakdown test should be enough?
Yesterday and today I changed the two onboard filters immedicately before and after the the mechanical fuel pump and the racor 92 micron filter. Racor didn't have any water in it. I am guessing if it doesnt' show up there it wouldn't be in the vst? Ran it today and it seems to be running better. no fuel smell and engine doesnt' seem to be surging/hesitating. Perhaps you are correct about the fuel? My guess/theory is that the filter clogged enough to cause issues withe the original old gas. Since then I have run new gas so the current tank has (mostly?) newer gas but the filter was still clogged. I will take it out on the water (just in the harbor) tomorrow to see if it still acts up. If it isn't fixed, the issue will show up almost immediately off the dock at approx 1400 rpm. If I have still have issues, I'll get a small tank to run fresh fuel.

All I can say is wish me luck!

[TownsendsFJR1300]

Of course good luck!!

Are you running ethanol fuel or non E-fuel? E fuel can cause issues within being a month old..



.

[mahtzo22]

Ethanol. Street gas. I generally run the boat at least 25 times per month, so it has never been a problem but she's been up for maintenance quite a bit the past year.

Thanks again.

[TownsendsFJR1300]

Did you get a chance to run it out on the water?

[mahtzo22]

Just got back. Ran great! Thanks again for your help. Next step is to take her out and use her like she is meant to be used!

There is one thing that I had forgotten amid all the concern over the miss/surging etc.

At the water intake where you put hte muffs, extremely small bubbles come out of hte vent. Initialllly upon startup there is more and they decrease at idle after a while. When revved sllightly the bubbles increase until the point where the exhaust out of the hub is strong enough so that you can't tell what the "micro bubbles" are doing.

Do you think that is an exhaust leak? if it is, Is that serious? (is that a stupid question?).

Thanks,
Louis

[pstephens46]

Just got back. Ran great! Thanks again for your help. Next step is to take her out and use her like she is meant to be used!

There is one thing that I had forgotten amid all the concern over the miss/surging etc.

At the water intake where you put hte muffs, extremely small bubbles come out of hte vent. Initialllly upon startup there is more and they decrease at idle after a while. When revved sllightly the bubbles increase until the point where the exhaust out of the hub is strong enough so that you can't tell what the "micro bubbles" are doing.

Do you think that is an exhaust leak? if it is, Is that serious? (is that a stupid question?).

Thanks,
Louis

Can you post a video? What vent?

[mahtzo22]

it is on the side of the lower unit (horizontal openings) roughly the same height as the prop. I cover it with the muffs when rinsing. I will try to get a video but don't think I can get a video this week. not sure when I can get one. Wish I had thought of it today when the boat was in the water.