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Repower 1986 15' Classic Sport Center Console
braxclark	#1  Posted on 05/01/20 - 1:11 PM
Member Posts: 4 Comments: 0 Joined: 05/01/20	Good day! I am doing some upgrades to a 1986 Sport Center Console interior and ready it for 11 year old twins to start making it there own. It is a special boat and I want my efforts to be just what it needed. I am wanting to repower the engine with a 4 stroke. When I purchased the boat years back it has a 1996 Yamaha 75hp 2 stroke. It is like new with minimal run time, but mama wants quiet and no smoke! I am looking for recommendations on engines for this size skiff as I WANT IT TO BE RIGHT and not run or drive poorly(porpoise) given my children are operating it. I need it safe and reliable. I am open to suggestions as I was looking at a new mercury 50-60hp or a Yamaha 60hp. Both brands are 4 strokes and weigh equally at 247 lbs. which is 1 lbs off from the 75 2 stroke I have on it now. Any help would be a huge help in our decision and any comments on things I should avoid or not do in the process of going to a 4 stroke. I just want it to operate at its peak and drive like it should without a lot of "rigging". Thanks in advance and hope everyone is well. Cheers!
Joe Kriz	#2  Posted on 05/01/20 - 1:41 PM
Site Owner Personal Page Personal Album Photo Albums Project Albums Posts: 11447 Comments: 452 Joined: 03/18/05	Yamaha F70 is the lightest and you already have the controls so you won't need to install or buy new controls. https://www.whalercentral.com/article...icle_id=77
braxclark	#3  Posted on 05/01/20 - 1:56 PM
Member Posts: 4 Comments: 0 Joined: 05/01/20	Thanks Joe! I was searching for something like that to spell it out! You are by far the seasoned veteran! Thank you. So the 70 hp yamaha wont weigh too much and cause it to porpoise while driving? It just seems awful big. The kids will end up using for water skiing, wake boarding, and such. Need to make sure it is propped right. Any suggestions on brand? One better than the other nowadays with regards to performance? Thanks again for all your help! BC Edited by braxclark on 05/01/20 - 2:05 PM
Joe Kriz	#4  Posted on 05/01/20 - 2:37 PM
Site Owner Personal Page Personal Album Photo Albums Project Albums Posts: 11447 Comments: 452 Joined: 03/18/05	Don't forget to add oil weight with your 75hp 2 stroke Yamaha. That would probably weigh more than the 70hp 4 stroke at 253 pounds. The older Evinrude 70hp 2 stokes in the past weighed 248 pounds plus the oil and container onboard. Others might be able to give you hands on experience with their 15' with that Yamaha F70. I know there are several members here with that motor. Also see this thread on engine mounting height: https://www.whalercentral.com/forum/v...d_id=26512
Finnegan	#5  Posted on 05/01/20 - 11:12 PM
Member Posts: 1926 Comments: 16 Joined: 05/02/08	The Mercury and Yamaha 50 & 60's are identical engine powerheads, same bore and stroke, both born out of the 1993 Joint Venture 50 hp models both offered back then. Yamaha then added dual overhead cams and 4 valves per cylinder to achieve the 70HP version. Mercury decided not to do it. It is probably only 1 or 2 MPH faster than either brand's 60. You would have to determine whether it's worth the premium extra price. For kids, if it were me, I'd look at the 50 HP or 60 HP as plenty of power for that hull, either brand, and the kids will be safer. All of these are basically the same engine, just different dress and color. My hunch is that the best overall cost/deal for the 15 is a 50 hp engine, about 35 MPH, especially for young operators.
braxclark	#6  Posted on 05/02/20 - 7:08 AM
Member Posts: 4 Comments: 0 Joined: 05/01/20	Thank you for the insight. I was thinking more 60 and see what you are saying. I have heard from others that if you are really dialed in you cannot tell the difference in the 70 except for the ride being a little "bow up". more money more weight for no real value. esp. with kids that are not worried about the detail like me! I had heard also what you were referring to on both brands being similar. Thank you again for the note. Anything else comes to mind fire away. Looking to make the call in the next week. having some gelcoat chips repaired then on to repower. The current 75hp Yamaha 2 stroke (1996) that is on there has never missed a service and is in tip top shape (wife wants less noise and no smoke) and runs like a top. what is that thing worth? When they pull it off they are going to send me home with it and I have no use for it. Not sure what it is worth to sell it. Thank you
Finnegan	#7  Posted on 05/02/20 - 12:19 PM
Member Posts: 1926 Comments: 16 Joined: 05/02/08	For water skiing, the choice of a 60HP engine is probably good, especially since you are changing to a 4-stroke with a little less acceleration power. As described your Yamaha 75 2 stroke is an engine in demand, and people are still looking to find one. I would ask 2800 and settle for 2500. It will sell! If you are selling it yourself, I would also sell it before you take it off the boat. Much easier to sell an outboard that way, and someone can see it run, etc. The buyer can then meet you at your new engine dealer, and the switch can be made easily. Don't get talked out of doing it this way. Be sure to clean up and buff the transom, with gelcoat if necessary, before the new engine goes on. Mount the new engine up in the third (from the top) set of bolt holes, or even the 4th. My guess would be the current engine is probably mounted too low. Same holes in transom can be used.
biggiefl	#8  Posted on 05/04/20 - 8:18 AM
Member Posts: 890 Comments: 4 Joined: 05/08/06	Are the twins going to be solo on this boat or will a parent/adult be present? I would not give an 11 year old a boat capable of 40+ speeds. What experience do they have boating? A yamaha will be able to use your controls and gauges and possibly wiring harness which will save you money. A mercury can use your yamaha controls but nothing else. 24 Whalers so far....
braxclark	#9  Posted on 05/20/20 - 6:51 PM
Member Posts: 4 Comments: 0 Joined: 05/01/20	Thank you all for your help and info. I am in line for 60hp 4 stroke to be installed. Got all the rails and wood of and replacing the mahogany. Finished the 2nd coat of west system epoxy then 4 coats of varnish. I appreciate the concern as well. I bought the boat to clean up and teach my children how to use it and when they reach the age and comfort they will be ready. Looking forward to the new engine and seeing how it turns out. Everyone was a big help in the project. I forwarded on the mounting suggestion as well always up for advise to make it right. Attach a pic when i am done. Any more suggestions are welcome! Thank you all. BC braxclark attached the following image: [111.08Kb]