Merc 500 holds back when warm

[dutchman89]

Hi guys,

When my merc 500 thunderbold is cold she runs perfect! With 3 people on board she runs up to 5100 rpm in a hartbeat. But when the motor is warm, the motor holds back. It takes a lot longer to get up in plane and tops at 4700 rpm. Also when i hit the throttle the motor holds back for a sec and then start climbing in rpm, but a lot slower then when she is cold.

Does anybody have an advice on what to do or check?

Need your help...

Greetings from Holland

 

[ckangaroo70]

Re: Merc 500 holds back when warm

Sounds like she may be too lean. Pull the spark plugs out and take a look at them. If they look like they have been burning real hot..then that would indicate the engine is being run lean. There are several charts you find online that will kinda give you an idea of what you want your plug to look like. I like a dark tan or even a lil bit of burnt oil showning, but if that plug is burning white or even a really light tan you are running lean. I have a 50 hp Merc Thunderbolt as well and you will really thank yourself if you take the time to get that thing dialed in just right. Remember to do your adjusting with the boat in the water. Trying to adjust an engine using muffs is not going to get good results. That engine needs to be dialed in on the water and running. Good luck.

 

[dutchman89]

Re: Merc 500 holds back when warm

Thanks a lot for your reply!

I looked at the plugs and they look clean. 1 of them was a bit black. I use 1:50 and normal fuel.

I recently cleaned out my carbs and reassembled them. Now I was looking around and I found this part (part 17 on the foto) outside the carb. Does anyone now what the function of this pcs is? Personally I think the motor holds back because it gets to little air/to much fuel. Does this part have an influence on those points?

Hope to hear from you!

Greetings from Holland