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Ask Noel Schembri Your Own Question
Noel Schembri
Noel Schembri, Marine Technician
Category: Boat
Satisfied Customers: 1951
Experience:  Advanced technical diploma
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2005 mercury 225 optimax I just installed on my 20' bass cat

Customer Question

2005 mercury 225 optimax I just installed on my 20' bass cat bass boat. It will fire right up and idle fin but when I go to the lake it wont get the boat on plane. I have changed spark plug, check fire and check compression all is good. What could be causing this problem of not getting n plane? And I have a throhy 24p 4 blade prop on it also.
JA: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Is there anything else important you think the Marine Mechanic should know?
Customer: no
Submitted: 10 months ago.
Category: Boat
Expert:  Noel Schembri replied 10 months ago.

Hello my name is ***** ***** I will assist you. The problem here could be with the air compressor. Take off the top cover and see if the belt of the compressor is still ok. If the belt is ok then next thing to check is the air and fuel pressure but to do so you wuold require some special tools. If you think you can check then please advise so that i will help you further.


Customer: replied 10 months ago.
I can check that. Can you tell me what tools and how to check it?
Customer: replied 10 months ago.
Do you think I have the correct size prop on this motor also? I took it off of the 1994 Mariner 200 motor that was on the boat before I put this optimax on.
Expert:  Noel Schembri replied 10 months ago.

I do not think it is a prop problem as it should be able to plain the boat with a 24 pitch prop. So yes what you need to do is to connect a fuel pressure gauge to the fuel and air line. The air pressure should be between 78 - 82 psi and the fuel pressure should be between 88 and 92 psi. If those are ok then next thing you need to do is to perform a cylinder misfire test by means of a diagnostic tool. Here you would need to check the air and fuel injectors one by one and also the coils, as if one cylinder is not running properly the engine will loose its power.


Customer: replied 10 months ago.
Something I forgot to tell you was that the first time I took it out and ran it at the lake it was slow but it did plane out and then the next time it would not plane out and finally got on plane.
Customer: replied 10 months ago.
Can I use a automotive fuel pressure gauge to check the fuel pressure? Do you have a diagram as to where I should connect to the air and fuel to check the pressure? And does the motor need to be running to check the air and fuel pressure or just turn the motorover?
Expert:  Noel Schembri replied 10 months ago.

Ok but still you need to follow that procedure as it seems that one of the cylinders is not functioning properly. Yes you can use an automotive pressure gauge. You would need to connect at the back of the engine where there are the bars of the air and fuel injectors, you have shnorr valves similar there.

Yes youy need to check it while running.


Customer: replied 10 months ago.
Do I check the air by the air valve that is on the back of the motor with a tire pressure air gauge?
Expert:  Noel Schembri replied 10 months ago.

You can use a tyre pressure gauge or the one you used for fuel

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