2003 Optimax 135hp primer bulb going soft when trolling.

[SteveOwen]

Hello guys.

I hope someone out there can help me. I have a 2003 mercury Optimax 135hp. Serial number 0T774550.

the issue is I’m getting air in my fuel system. If I’m trolling at 1200rpm the engine seems to use more fuel than what can be delivered. If I try and get it up on plane after 10 mins of trolling it will cut out. Then I need to pump up the primer bulb and it will fire straight back up.
She will sit on plane all day. As long as I’m over 3200rpm it runs get and will rev out to 5300rpm with no issues.

I’ve replaced all 3 fuel pumps and I’ve removed and checked the tracker valve and fuel pressure regulator valve. Both look to be in good condition.

The boat was sat for 7 years before I bought it. Good engine compression. Around 120psi.

[EuropeanAM]

Pulse pump needs to be rebuilt and/or any of the following:

-Broken reed

-Low compression on one or more cylinders.

[SteveOwen]

Cylinder compression is good on all 6 cylinders. I’ve fitted a new pulse pump, it was after market thought.

In regard to the Reed valve, would I experience any other symptoms? It idles perfectly and it runs very smooth.

thanks.
steve.

[EuropeanAM]

Aftermarket pump will not do the job... either get a new OEM pump, or a kit to rebuild the original OEM. Check valves and diaphragms in the aftermarkets just don't function the same.

You might not even realize a reed was broken or damage.

[JOE54]

STEVE optimaxengines will run surprisingly well with a broken reed valve

[SteveOwen]

Thank you for the info. Do you supply Mercury parts? Ive had a quick look online and dont see too many genuine parts available. Id also fit the reeds as well. Steve

[JOE54]

contact EUROPEAN MARINE one of the sponsors on here thier banner is in post 2 and 4 pump kit # 857005A1

[SteveOwen]

Quick update. I fitted a genuine diaphragm fuel pump and it seems to of fixed the issue. I took her out for a few hours at 1200rpm yesterday and it didn’t cut out once. I’ll post again after a few more runs. Thanks to EuropeanAM for you support.

[JOE54]

amazing isnt it

[SteveOwen]

I can completely confirm it’s fixed now. Been out 5 or 6 times with no issues. I’ve seen this issue on other forums but no one has declared their boat was fixed. So here you go.
thanks again chaps. Fair weather to y’all.

[JOE54]

just cooler will be fine with me

[SteveOwen]

Same. It’s 105 here with no wind. You need to bring doing 30mph on the boat or in the water. Anything other than that and you’re melting.