Optimax issue?

[James31]

2018 Optimax Pro XS 150 hp, serial# 2B532368

I have a 2018 Optimax Pro XS 150hp. 2 weeks ago, I was fishing on a rather warm 85° sunny day, but we had a cold front coming in midday. When the front got there, it had rained heavily for about an hour and the temp dropped fast into the low 70's and continued dropping throughout the day. But, that 15° drop in temp was within the first 30-45 minutes. I do not know if this will be relevant information moving forward or not.

The motor ran perfectly fine up to that point. After attempting to start the motor back up following that temp drop, it did not want to stay running. After checking, I had lost prime to the engine. I primed the bulb, and she fired right back up.

The next outing, the boat was hard to start. It took about 3 times to get it to sputter where I gently brought the RPMs up to about 800 for about 30 seconds. She seemed to do ok after that, it did seem a bit harder to start after fishing a while, but ran just fine.

At this point, I'm chalking it up to having 195hrs on this set of plugs and my filter is at 95 hrs. I figured the weekend before, fishing in the rain with the dramatic temp change and having about 12 gallons of fuel in my 41 gallon tank could've gotten a lot of water caught in the separator.

I swapped the separator/filter with a new spare I keep in the boat after getting back to the house that day. After putting the muffs of, she fired right up and idled perfectly. I thought that was the issue.

This past weekend, I took the boat out again, and again, it was difficult to start and keep running at first. Again, feather the RPMs a bit, and it seemed to do fine. I had put fresh gas in my tank along with a bottle of quick clean (which I run the quick clean every 3rd fill up and always run the Lucus marine stabilizer/cleaner with every tank of gas). My goal was to just run the boat. I burned about 30 of the 41 gallons running at various RPMs from 4200(minimum RPM on plane) to 5650 (WOT).

After about an hour and a half of running, I shut the engine off and trolled around a bit just messing with the livescope. I'd guess that I had the engine off for about 2 hrs. She fired up on the first crank. Cool, I was thinking she was fixed at this point.

I made the run back to the long no wake zone leading into the marina. About 45 seconds after setting the boat down and idling in, she started sputtering again. It isn't rhythmic, but a random miss. If I touch the hot foot it minimizes the shutter and above 1000 RPMs it is running fine, no loss of midrange or top end performance.

I got back home, and noticed that the bolt on my pulse pump had came completely loose, like to the point that it should've fallen out if a wiring harness wasn't blocking it. Thinking to myself, "this has got to be the culprit" I tightend the bolt up and put her on the muffs. Again she fired right up on the muffs.

I went back to the lake and yet again. In the water, she is difficult to start initially. Then idles fine until I put it in gear where she will sputter and miss until I bump the RPMs above 1000?

No I have not changed the plugs yet. That was my next step, but when I pulled them and they looked "good" with the exception of being a little ashy. Which I assume is from a lean idle situation.

My guess at this point would be the pulse pump was likely damaged from the bolt coming loose and it's not keeping the fuel supplied properly at low RPM. I mainly think this because it idles fine after a run for about a minute, then begins stuttering again.

Sorry for the long post, but I feel that details are important and I wanted to provide all the information that I know at this time.

Anyone experienced anything like this, or have any ideas that I may have missed? I am very mechanicaly inclined and have always did all my own work on the older engines, but I've opted to alway have this one done professionally. Unfortunately, all the local shops are 6 weeks or more out.

[SilverFox579]

Pumping the bulb prior to every engine start? Should be.

Spark plugs are long overdue for replacement, service interval is annual or 100hrs whichever comes first. You should be using Quickare (or Quickstor if appropriate) and Quickleen in every tank of fuel, 1oz each per 5gals fuel, 87 octane only. See the FAQ at the top of this forum for several excellent DIY topics, a few key ones linked below.

Oil, Battery, Spark Plugs, Fuel and Fuel Additive Recommendations

Recommended Annual Maintenance or Winterization for Optimax Engines

Compressor STRAINER Cleaning

[EuropeanAM]

Good suggestions for the above links. Let's keep this brief: You've got some OVERDUE items to address.

Please follow each of the below links EXACTLY as suggested, without deviating. Follow the Recommended Maintenance from here on out:


FUEL LINES AND PERFORMANCE PROBLEMS


Recommended Annual Maintenance for Optimax Engines

[James31]

Good suggestions for the above links. Let's keep this brief: You've got some OVERDUE items to address.

Please follow each of the below links EXACTLY as suggested, without deviating. Follow the Recommended Maintenance from here on out:


FUEL LINES AND PERFORMANCE PROBLEMS


Recommended Annual Maintenance for Optimax Engines

I always prime before initially starting. The 1st time it was hard to start, I assumed that maybe I had gotten sidetracked and failed to properly prime the fuel.

Up until last years 100 hr service, the plugs and water pump have been part of the service. However, last year the guy that's serviced my boat since it was new, stated that the plugs (and water pump) are part if the 300 hr service and was not needed. Especially, with this year being my 300 hr service. I did insist on the water pump because I am a dirty water angler and the motor sees a lot of sand and debris. Also, because I fish grass lakes and areas with a lot of debris, the compressor strainer is something I do at least monthly along with a good 20 minute back flush.

I thought that I've read somewhere that the plugs should've been every 100 hrs, probably on here when I was researching when I first got the boat. Everything else should be up to date for PMs. I will be replacing the belt, plugs and pulse pump this weekend.

The fuel line has been replaced, although it was replaced with black alcohol resistant fuel line. The grey fuel line had NOT deteriorated yet.

I have been running the Lucus marine stabilizer over the Merc stuff simply because it is available. It's supposed to have "cleaner" in it, which is why I've always ran the quick clean every 3rd tank.

Now, about the fuel? I've always ran ethanol free whenever possible, sometimes it just isn't possible. I'd say out of maybe 400 gallons a year, less than 100 gallons would be 87 octane E-10 the rest of the gas was either 89 or 90 octane rec fuel. Should I stop that and just start running 87 octane E-10?

[EuropeanAM]

Missed about 85% of the "Fuel Lines and Performance Problems" steps. Strongly suggest you go back and do them EXACTLY as described, don't substitute materials or skip ANY item.

Plugs, filters and maintenance (including the water pump) are shown in the Maintenance section of the Owner's Manual, Service Manual, and of course, the links provided above.

As for fuel and additives: The info provided is based on TENS of thousands of injectors we've seen. At about $800 a pop now, anything you can do to help protect those little round gems we call Direct Injectors is a good investment. We've provided (in detail) the best information and results we have seen: You get the information for free. And if you choose to go a different route and use different fuels, different additives, or nothing at all, that's absolutely your choice.

Just know we've provided you options to best protect your investment. Choose wisely. :)

[Aj14]

Engines are expensive.
You just got some free advice from Don and Silverfox.
What you do with that advice is now up to you. I would take their advice.
Welcome to BBC.

[James31]

Don, please do not take anything I've been saying as argumentative or contradictive. This is showing my ignorance of this "modern" motor, I am here to learn from those who know this motor better than I.

As far as the fuel additives, I will make the switch on my next fill up. I will also begin swapping the prime bulb, fuel line and pulse pump over this weekend.

If I am reading the fuel line recommendation correctly, I need to swap my 3/8" line from the prime bulb over to a 5/16", then have it directly hooked to the pulse pump? Currently, either from factory or rigging from the dealer, there is a barb/union as the fuel line enters the lower cowling. I've questioned that myself as being a restriction or additional failure point, but the mechanic insisted that I leave it there.

As to my selection of fuel additives, I've always ran fuel stabilizer in one form or another in every boat I've owned. I was merely continuing that trend with this motor. When I bought the boat, the mechanic told me to run Quickclean every few tanks.

The boat really doesn't set much as I use it basically every weekend year around with the exception of deer season, and even then, I still run it a couple times a month Sept-Nov.

[JOE54]

do away with the connection on the fuel line , OEM bulbs are 3/8 in and 5/16 out to pulse pump connector is a potential problem for sure , swap to cocktail in fuel , be October before you know it

[James31]

Update so far.

I have not swapped the fuel line to the OEM line, or replace the pulse pump, that will be done this weekend when I'm able to obtain the supplies.

I did swap the prime bulb and replace the 3/8 fuel line with some 5/16" I had and directly hooked it to the pulse pump. Eliminating the barb/union that was originally there as a temporary thing to do a "test run" until I get the OEM line.

I was able to go ahead and replace the belt and plugs last night. (The old belt had definitely stretched.) Properly gaped the plugs between 0.041" and 0.043". I measured this gap with a "pin gauge" I had my son (a machinist) turn down and polish on a lathe at his work. I confirmed the thickness at 0.042" with my mics prior to checking the plugs.

As a side note, after pulling the old plugs, I cleaned them up to remove any carbon and they were all over the place. All of the old plugs were gaped too small for the pin gauge. According to the little gap tool you get from Autozone, they ranged from 0.027" to 0.038", with 4 of the 6 falling around 0.035" +/- 0.002".

After completing what I have done so far, I primed the bulb, kicked on the key for the pump to engage, squeezed the bulb again, engaged the pump again, and turned the engine over. The same problem occurred. Crank, crank, crank, fire, stall. Again, crank, crank, crank, fire, sputter, but remained running. I had my son squeeze the prime bulb while she was sputtering and it began idling smoothly a few seconds later.

I immediately shut off the engine (it had only been running maybe 20 seconds, yes I had the muffs on) and let it set about 10 minutes. I turned the key over again and it instantly fired back up. This is the same symptoms it has been having on the muffs and thus far has been creating an issue when in gear on the water.

Considering how quickly it smoothed out when the prime bulb was squeezed while it was sputtering, I'm leaning more towards a bad pulse pump that isn't supplying enough fuel to the VST at low RPMs. But, then again, I don't quite understand the hard start? Shouldn't the pulse pump only show symptoms AFTER the engine starts?

Again, I'm trying to learn more about how this system works and I'm kinda thinking out loud while keeping you up to date on progress. I'll post another update tomorrow after I get the OEM fuel line and pulse pump installed.

Thanks for the help so far.

[JOE54]

if the pulse pimp diaphragm has a hoe in it you are pushing raw fuel into crank case via the pulse hole and hose that activates diaphragm , generally this causes rpm flair at startup , does negine smoke when it cranks ???? do you have a set of gages (correct ones ) to test fuel/air psi for bleed off you possibly have a failing diaphragm in one of the rails very common on optimax engines

[EuropeanAM]

If your problem is on the supply side: And you don't follow the directions provided earlier EXACTLY as described (rather than trying this, then trying that, then changing this, then going and getting that), you may very well spend the entire season chasing something that you've literally moved from one bad component into a new component, and later into another.

That's as clearly as I can state it. Please report back after you've done ALL of those items, ALL NEW, ALL AT THE SAME TIME.

[James31]

if the pulse pimp diaphragm has a hoe in it you are pushing raw fuel into crank case via the pulse hole and hose that activates diaphragm , generally this causes rpm flair at startup , does negine smoke when it cranks ???? do you have a set of gages (correct ones ) to test fuel/air psi for bleed off you possibly have a failing diaphragm in one of the rails very common on optimax engines

I do not have the gages to check air/fuel pressures.

Yes, the engine revs up a small amount when it first starts. If it smokes at startup, it is a very small amount.

[James31]

Fuel line system setup replaced with OEM parts, new pulse pump replaced.

Still experiencing the same symptoms.

The guy that had the pulse pump told me to check the shrader valve on the air side while experiencing the issue. If gas comes out, it's most likely the air/fuel diaphragm.

I checked that, and had raw fuel come out of the air side. I pulled the diaphragm out and it is indeed cracked. I found one locally (expensive little things). On my way back to install new fuel/air diaphragm.

[James31]

That fuel/air separator diaphragm was the issue. The boat ran perfectly after I was able to get it started.

[JOE54]

"revs up" now you know why i asked

[James31]

"revs up" now you know why i asked

Thank you!

In the videos that I saw about troubleshooting that diaphragm, the motor would fluctuate badly at idle. Mine wasn't doing that, so I discounted that as the issue. My motor would rev up, but less than a second before settling down. Also, I did not notice any smoke outside of my garage, presumably due to the wind, but when I started it inside the garage, you could definitely see it.

[JOE54]

glad its fixed

[SilverFox579]

Thank you!

In the videos that I saw about troubleshooting that diaphragm, the motor would fluctuate badly at idle. Mine wasn't doing that, so I discounted that as the issue. My motor would rev up, but less than a second before settling down. Also, I did not notice any smoke outside of my garage, presumably due to the wind, but when I started it inside the garage, you could definitely see it.

This is the best place for correct advise with an Optimax, most videos you find online or the 'tube won't help much if any at all.

[JOE54]

and its free

[SilverFox579]

and always correct.