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I have a 97 Mako with a 115 Merc. I have maybe 50 lbs of equipment. With 2 people, it has trouble getting on plane. It feels like its "Spinning Out". Also, the throttle is kinda funky. It dosnt accelerate smooth. When I give it gas, it picks up a little then BOOM, it all of a sudden picks way up. Is this my throttle linkage?? I've taken the cover off and gave it throttle by hand on the carb and its smooth. Anybody??????
Sounds to me like you've got a "spun hub" in your prop.
The prop has a sleeve that fits just over the prop shaft. Just ouside of this sleeve is a chunk of rubber that surrounds and secures the sleeve to the inner hub of the prop. Most likely, the rubber has broken loose from the inner hub of the prop. Remove the prop and look for any signs of chewed rubber around the sleeve or inner hub. You may also try spinning the prop by hand w/ the engine in gear (but turned off). If it's a spun hub, you should be able to turn the prop before you feel the motor go through it's compression stage.
It's cheap fix, around $40, that most prop shops can take care of for you in a day or less. If the blade edges are dinged up, have a total recondition done for about $80.
Does it feel like the throttle linkage is actually binding or do you mean that the tension remains constant and the engine all of the sudden revs way up as you push the throttle down further? If the latter, that would be when the engine reaches the point where the prop hub slips.
It's in neutral when I did it. When I am coming in and slowing down, right before I hit idle speed, I hear a noise from the motor, sounds like it comes from the foot, like a ratteling sound. Other than this the boat is awsome. Once it planes out, it cruises fine. And I have learned that when Im slowing up, I can move the throttle into a specific position to keep it from ratteling.
How about a little more information - gps speeds, tach readings, prop size (diameter and pitch) and material? I think that motor idles on two cylinders and switches to 4 cylinder mode around 2500 rpm, which would account for the power surge, I've heard other Merc. inline 4 owners complain about that before.
I dont have GPS speeds. Dont know why I havnt checked it. Not sure about the prop. I know its stainless. And Im not sure about engine speed. I know that when getting on plane, I give it "Alot" of throttle then back it off when it planes.
Dave - I'm in Columbia - if you want I'll be glad to look at it and see what the problem is. Just shoot me an e-mail or let me know how to contact you.
Nah, that's a good question finlanderrr. But yes, I do trim it down. I really dont think I have a big problem. I just think that Im soooo used to bass and ski boats that It feels awkward. BTW, I put it in gear and it was very hard to turn the prop.
I think that you are right. If the prop was spun you wouldn't be able to get up on plane (certainly not more than once or twice) when they're done they're DONE. I think trim tabs and/or a planing aid might help you and I do think the low rpm running qualities of that motor are affecting you also as I mentioned in my previous post(I wasn't joking - that motor really does run on 2 cylinders until it gets up to a certain rpm).
I knew you were serious. I've heard of the before. What I have been noticing though is that alot of the 171's have 90 hp motors on them. If those do the job, why is my 115 so slow out the hole?
1st I think that 90 is a 3 cylinder w/o the strange 2 cylinder idle, but that's why I was asking all the other information in the 1st post - you may not be propped correctly, but its just speculation till we have some more information....
Hey Dave,
Chris from Venice here. I just upgraded from a 1987 17' CC Mako w/ a 115 this last summer and can tell you that the only time(s) that I ever had trouble getting on plane (even when it was outfitted w/ a 90Hp) was when I had lost compression due to a failed VRO which ended in a powerhead rebuild. TRy a compression check yet?
Simple and inexpensive. The only other time I had planing problems is when the hull was filled with water due to a mis-cuminication about the bildge plug with my air headed girlfriend - 16 miles offshore & after a 35 min. dive!!
97 Mako 171 CC Planing???
