1998 5.7 Merc Tach problems

[spearops]

I recently had some work done on my carb and while the mechanic was test driving the boat the engine was getting 40mph and only turning 3600 rpm at WOT. I explained that this engine and the previous engine had the same reading at WOT. He sugguested switching the prop from my current 19p to a 17p which I did. The engine seems to run smoother but still only getting 3600rpm at WOT. I expected the rpm to jump up about 600rpm or so. I am trouble shooting and the common denominator to this engine and the last engine is the tach. It is a teleflex international and has setting in the back for 4c/2p, 6c/3p, 8c/4p, 5p and 6p. I naturally selected 8c but is this the correct setting for this engine?

 

[John_S]

Re: 1998 5.7 Merc Tach problems

I recently had some work done on my carb and while the mechanic was test driving the boat the engine was getting 40mph and only turning 3600 rpm at WOT. I explained that this engine and the previous engine had the same reading at WOT. He sugguested switching the prop from my current 19p to a 17p which I did. The engine seems to run smoother but still only getting 3600rpm at WOT. I expected the rpm to jump up about 600rpm or so. I am trouble shooting and the common denominator to this engine and the last engine is the tach. It is a teleflex international and has setting in the back for 4c/2p, 6c/3p, 8c/4p, 5p and 6p. I naturally selected 8c but is this the correct setting for this engine?

Welcome to iBoats.

8c should mean 8 cylinder which is correct for 5.7L. If it was on 4c or 6c, the readings would have been higher than actual. If it was on the 5p or 6p, that may explain the low reading. Doesn't explain why it didn't change though, so might need a new tach anyway. Best just to compare to a shop tach, to make sure.

 

[Don S]

Re: 1998 5.7 Merc Tach problems

You need to get a shop tach and verify the rpm of your tach.

 

[Burns363R]

What did you ever find with this? What did you end up setting your tach to?

 

[GA_Boater]

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