Needing help 1993 40hp Mercury higher rpm issues

[LacyAllen]

First off thanks for having me I am new here. I have a 1993 crest 2 21' small tubes pontoon I have issues since I bought it 2.5 years ago there was little to no forward movement when just off idle I was told that the hub was slipping in the prop I bought a new hub and prop. Nothing changed changed the lower unit(21") out with a used unit. Big difference I now have low to middle rpm but still full throttle it is like it loads and unloads I tried to trim either up or down and it didn't seem to make any different I need help.

 

[HotTommy]

You may have more luck posting your question on the forum here on Iboats.com that deals with the specific brand of engine you have. Click on the Forums link at the top and pick the Mercury outboard forum.

 

[LacyAllen]

You may have more luck posting your question on the forum here on Iboats.com that deals with the specific brand of engine you have. Click on the Forums link at the top and pick the Mercury outboard forum.

I will do so thank you

 

[ahicks]

You may have an issue with the motor mounted too high on the transom. High enough where the propeller is getting a mixture of air and water rather than the all water supply that it needs.

We might be able to help with that (confirm or deny) if you were to post some pictures that would clearly show the height of the motor in relation to the boat.

 

[LacyAllen]

I won't be back up to the pontoon till this coming weekend. I will try and get some photos. I am guessing you wanting the motor sitting basically straight up and down and then a side photo of mounting area?

 

[ahicks]

Yup, that would work.

 

[LacyAllen]

I will do my best we have a chance of rain all weekend, we need the rain for the lakes are way down but the timing well it could do it during the week.

 

[LacyAllen]

 

[HotTommy]

At first glance your engine does not appear to be mounted too high. Most folks start with the anti-ventilation plate (just above the propeller) about even with the bottom of the engine pod that supports the transom. When underway, the anti-ventilation plate should be a couple inches below the water.

Assuming this is not an engine problem (and it may be), your symptom sounds like something is intermittently interrupting the flow of water to the propeller. Check for anything that might cause that. ... If the problem is not at the propeller, it may be something like a restricted fuel flow problem -- enough fuel for lower RPM but not wide open throttle. If your fuel line has a bulb on it, try pumping it when the symptom arises and see what happens.

 

[ahicks]

Very difficult to see much due to the reflections, but I don't see anything jumping out at me as far as glaring errors. Motor height looks fine.

I am left wondering though regarding the function of that chain and float. What is that used for?

Have you had anyone local look at this? Maybe a mobille marine service? Do you know what size prop is on it?

There's no tree branch or anything else fouling up the water in front of the prop is there?

 

[LacyAllen]

At first glance your engine does not appear to be mounted too high. Most folks start with the anti-ventilation plate (just above the propeller) about even with the bottom of the engine pod that supports the transom. When underway, the anti-ventilation plate should be a couple inches below the water.

Assuming this is not an engine problem (and it may be), your symptom sounds like something is intermittently interrupting the flow of water to the propeller. Check for anything that might cause that. ... If the problem is not at the propeller, it may be something like a restricted fuel flow problem -- enough fuel for lower RPM but not wide open throttle. If your fuel line has a bulb on it, try pumping it when the symptom arises and see what happens.

We haven't tried pumping the fuel bulb yet but he has tried a different fuel tank a new fuel line and bulb and went through and replaced I think all.the fuel lines leading to the carbs he said something about taking off them next maybe. ( also kidded about using the motor as a boat anchor) thanks for the help

 

[MRS]

What is the chain hooked to?

 

[LacyAllen]

What is the chain hooked to?

My anchor