Figure this one out?!

[EdSmith]

I bought a pontoon boat from auction recently. It has a 2007 115hp 4 stroke with a new, unused lower unit. When I move the throttle control forward the boat reverses and move it back it goes forward. I have checked the linkage, throttle con*****er and, yes, even the propeller. Is there a chance I have a counter-rotating lower unit? If so, how would I know and is the best solution at counter-rotating propeller?

[hanksvilleman]

Lower unit.

I'm not sure about your motor, but I do know that on Mercury there is a sequence to removing and reinstalling the lower unit that makes it a lot easier and to make sure it shifts correctly. I would suggest finding out if there is a sequence that needs to be followed and remove the lower unit and reinstall using what you have learned. If anything, you can check the impeller while you're there.
If there is not a sequence, then the prop is probably the problem.
Hope this helps,
Dave

[99yam40]

I have checked the linkage, throttle con*****er and, yes, even the propeller. Is there a chance I have a counter-rotating lower unit? If so, how would I know and is the best solution at counter-rotating propeller?

Is your motor a counter-rotating one with a regular lower unit or a regular motor with a counter-rotating lower unit?
could be a linkage problem if the wrong lower unit was installed the linkage maybe different for the 2
If it is a counter-rotating lower unit the cheapest solution would be the counter-rotating prop, but you need to be sure of what is going on.
The thrust loading on the lower unit maybe a problem

Look at the parts break down for the motor and compare

[robert graham]

99yam40 may be on to your problem, and they could have just stuck the wrong prop on your lower unit, should be very easy to check. If that's the case, then maybe buy the correct prop. Hope that's it and turns out to be an easy/cheap fix!