Primer bulb on Optimax 150

P

Propofloor

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Jan 20, 2019
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This is probably a pretty dumb question. How firm should the primer bulb get on an Optimax? I know with carbureted motors the float would close and the bulb would get firm. Should it be that firm with Direct Injection. I am having some issues with my motor idling rough and missing hard when over 4000 RPM. Changed the spark plugs and fuel separator/filter which were incredibly dirty and full. After that I noticed the bulb does not get firm with the motor off. If I clamp the line right before the motor it gets firm however, just wondering if this is part of my problem. Haven't been out since changing the filters, hoping that is all my problem is.
 
wrench 3

wrench 3

Commander
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Aug 12, 2012
Messages
2,108
The fuel is pumped into a vapor separator that has a float and a needle valve just like a carb. The fuel injection system then pumps the fuel out of that reservoir. So the bulb should feel similar to a carb system. There may be a little air trapped in the top of the fuel water separator but it should clear when the motor gets some running.
If the filter was in really bad shape it may be a good idea to drain the vapor separator. There should be a drain plug on the opposite end of the vapor separator from the filter.
 
M

Marine Services of Las Vegas

Seaman
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Mar 7, 2019
Messages
53
Where do you live? Are dirt dobbers prevalent in your area? In one of the images with the red arrow, at the base of the PH (you'll have to seperate the bottom cowl) is a picture of the discharge hose. This is where the compressor residual air exits the fuel/air system. If clogged could present issues... Take a fuel sample in the one labeled opti vst drain, the needle could be distorted (similiar to float level on carbs and we all know that the float is the most critical setting in a carburator. Do you have the cds software with the smart comms box? But most of all compression, compression, compression...
Have you done a compression test? You can't look at the reeds without pulling the plenum...when was the last time the engine ran good? If someone primes the bulb does it help, what size prop,

I will send you some suggestions via pm...I'm not posting any more visible images on the forum until the site administrators fix the problem I have addressed...
 
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Propofloor

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Jan 20, 2019
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Compression was fine when I got the boat a few months ago and had it checked. At that point it had a 3 blade prop on and I switched it to a 4 blade power tech 20 pitch. Actually when I switched the prop is when the issues started, but I am not sure how this would be a prop related thing the way the RPMs fall. I will check the things out you stated. I emptied the separators into glasses and they were filthy by the way. I have put about 50 hours on the boat in the last few months. Honestly you would never even know there is an issue until you go wide open. The motor is on a Pathfinder 1900v and I don’t have it opened all the way very much. I am usually cruising 32 MPH at 3000 RPM and have my wife and kid on board so I am not flying around the shallow water we have in SW Florida. I could ride the boat all day now and not notice anything unless I tried to pin it.
 
M

Marine Services of Las Vegas

Seaman
Joined
Mar 7, 2019
Messages
53
Propofloor said:
This is probably a pretty dumb question. How firm should the primer bulb get on an Optimax? I know with carburetor motors the float would close and the bulb would get firm. Should it be that firm with Direct Injection..
Click to expand...

But to answer your question yes it should get firm...FYI in that picture I sent you about the VST, if you know your boat is going to sit for long period of times I would drain that into a suitable container. The worst thing you can do is let it sit, FYI more blades to not equal better performance...in theory the most efficient prop is a one blade but do to its counteractive balance it is not practical. 3 blade quicker hole shot 4 blade more stability. I'll pm you a informative bulletin on props.
 
C

Chris1956

Supreme Mariner
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Mar 25, 2004
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28,571
20" pitch prop on a 19 footer with 150HP could be a bit overpropped. Can you put the old prop on for test purposes?
 
P

Propofloor

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Jan 20, 2019
Messages
12
Chris1956 said:
20" pitch prop on a 19 footer with 150HP could be a bit overpropped. Can you put the old prop on for test purposes?
Click to expand...

I will try out the old prop this weekend. Do you think that a prop could cause this type of problem? I have never heard of the prop causing bad RPM drops like this. It's almost like I am running out of gas, or hitting a rev limiter.
 
P

Propofloor

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Jan 20, 2019
Messages
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I believe I have found the solution to my problem. There was a section of the fuel line that was corroded and the inner liner was collapsed and severely restricting fuel flow. It was difficult to see without taking the fuel line off and holding it up to the light to look through it as it was not on the ends of the line. I took the boat out for about an hour today and ran it WOT for a while with no problems at all with myself on board. Thank you all for your help.
 
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