Johnson 70 2 stroke only reaching 3500 rpms at WOT

[jakedaawg]

Ohhh okay didn't know they were numbered lol. Is there a way to test the max WOT timing?

A timing light

 

[Jimmyb617]

Has this boat ever run well that you "personally" witnessed?

What size prop do you have on there? A 70 on a 17 ft wellcraft is horribly under powered. I would expect about a 11 or 13p.

How old is the boat? Has it lived outside? Boats get waterlogged. They can look beautiful but weigh an extra grand or so. There is no way to get the water out of the foam.

If the carbs have been cleaned, its got compression and spark, and nobody messed with the linkage then its something else in or on the boat.

Have you checked Max timing?

If I did try a new sized prop do you think that would really increase the RPMs or would it not matter because there is not enough power anyway

 

[jakedaawg]

No point in a prop till post #14 Is done. Then it's just up to you. I have a couple more suggestions but things must be done in order.

 

[cfauvel]

Has this boat ever run well that you "personally" witnessed?

This is question was important...without a baseline, there is no way to know if the engine is running fine and just under powered or over propped....or if there IS something wrong with the engine...I wish the OP well...maybe time to think about getting a replacement 115 or 130 hp.