'73 150hp bogging down.

[wekenav8r]

This engine was serviced by a Mercury mechanic. The compression is an even 120 lbs on all six holes. After a series of troubleshooting tests, including tearing down the carbs a couple of times, the powerhead was removed and the exhaust tuner was found to be in pieces, and was replaced with a used part. The engine starts right up, and idles great. Put it in the lake it will only make 3800 rpm, boggs down and hesitates under load. Seems worse after it warms up (a rich condition). The mechanic gave up on it. Another mechanic checked it out for me, and thought the #3 plug was too clean, maybe sucking water. Suggested that the used exhaust tuner might be warped, and should have been resurfaced before it was installed. I have a manual on this motor, but can't even find a diagram or picture of this part in question. Can anyone help? Thanks in advance!<br />Tim

 

[Clams Canino]

Re: '73 150hp bogging down.

Perhaps it's as simple as being over-propped. Try dropping a few pitches and try again.<br /><br />-W

 

[wekenav8r]

Re: '73 150hp bogging down.

That's been checked too. My mechanic put on a smaller prop to see if it would rev up, replaced the fuel pump, checked all the usual things. The engine just acts as if it's too rich. All six plugs are firing at WOT, and the carbs are all working and not leaking. If anyone who has pulled the powerhead on one of these could tell me what an exhaust tuner looks like, and how it is attached to the powerhead, I'd appreciate it. I'm almost ready to pull the powerhead off now. <br />Thanks for your reply clams.<br />Tim

 

[wekenav8r]

Re: '73 150hp bogging down.

It was also suggested to me that bad reeds could cause this, one cylinder leaking compression into another?

 

[Clams Canino]

Re: '73 150hp bogging down.

Bad reeds show up FIRST as an idle issue. Also anyone check the size of the main jets? They outta be .080<br /><br />-W

 

[stant1man]

Re: '73 150hp bogging down.

What exactly is an exhaust tuner?

 

[wekenav8r]

Re: '73 150hp bogging down.

I've had a couple of mechanics tell me that the exhaust extension is not my problem. I think I've narrowed the cause down to water entering the combustion chamber at speeds above idle (since it seems to idle fine). I've had a mechanic pull the exhaust cover and plate and don't think that's the problem. Could it be the bottom main seal?<br />Thanks, Tim