Spark advance arm adjustment 75 horse Mariner

[starkyb]

Got my boat back from some carb service and the mechanic adjusted my timing. Now I have lost some of my top end, about 500 rpms worth. I also notice that it vibrates intermittently at wot. It just doesn't have the umph it used to. All the adjustments he made in a tank but he never put it on the water. Could some minor adjustments of the spark advance help or am I barking up the wrong tree?

 

[CharlieB]

Re: Spark advance arm adjustment 75 horse Mariner

You paid to have it done, you should not be changing anything.

Return it and tell him exactly what you have told us.

He may have retarded the timing a couple of degrees to allow for a lower quality fuel. Depending on your area that may not be a bad thing, but generally the fuel in the U.S. is acceptable to most all motors.

 

[starkyb]

Re: Spark advance arm adjustment 75 horse Mariner

Unfortunately I don't have that much confidence in his ability. I was hoping to take it out on the water and tweak it myself. I was hoping to get some advice on how to do it myself. I can do it in a little bit of time as opposed to driving it to him and waiting for him to do it. I would still have use of my boat.

 

[Texasmark]

Re: Spark advance arm adjustment 75 horse Mariner

I have a 90 triple like your 75. My manual covering our engines says that idle advance is about TDC and WOT is 20 BTDC at cranking speeds.

You really to get a manual as the timing sequence is somewhat involved. Not complicated but there are several parts to the linkage which must be lined up properly to get the timing right.

Mark