x-long shaft V6 Merc on long shaft transom

[kcrafton]

I have a quandry. I have a line on a nice '99 135 HP Optimax in which I can upgrade the ride on my 18' fish/ski boat and the price is right. The problem is the Optimax is an X-long shaft and my boat is not. I saw several posts on this site relating to this subject and the best I can determine is that a jackplate may allow this motor to work. The boat is rated for a 150 HP so it is not overpowered but what may happen raising the motor 5" or so with a jackplate? I am not into performance -- I am not one who runs down the lake wide open and I am not doing this for the increased speed. I am looking forward to a more reliable, less gas-burning engine than my current 115 hp inline 6 Merc. I saw some opinions that handling and performance could be compromised by raising the weight the extra 5" or so but with my expectations would this work? By adding a jackplate and raising the motor as such would it put additional stress on the transom? The weight difference in the two motors is approximately 125# so that is a jump already. Any insight into this opportunity would be greatly appreciated. I don't have any experience along these lines to make a good decision.

 

[DJ]

Re: x-long shaft V6 Merc on long shaft transom

kcrafton,<br /><br />Look for another engine. That 5" is a LOT to bridge. It may have to go even higher to perform correctly.<br /><br />You're right, it will stress the transom and may cause handling issues.<br /><br />Sorry!<br />

 

[kcrafton]

Re: x-long shaft V6 Merc on long shaft transom

DJ, <br /><br />I appreciate your input. But specifically what kind of performance or handling issues might I run into with the xl shaft and a jack plate? It would seem to me that if you get the motor at the right height there shouldn't be any issue with planing or cavitation. Would the "balance" of changing the weight distribution add a different kind of handling or performance issue? I saw a reference to "chime walking" but I am not familiar with what that means.

 

[DJ]

Re: x-long shaft V6 Merc on long shaft transom

KC,<br /><br />You will have a rather large powerhead sitting well above the boat. That can cause a top heavy issue.<br /><br />Chine walking is the side to side rocking of the boat at higher planing speeds. The powerhead sitting high will make it worse. It can get violent.<br /><br />Even if you do get the height right, you will have a great cantilever effect on the transom of the boat. That will push the bow down. Not to mention structural issues created by the engine pushing down and forward instead of just forward.

 

[MFG197]

Re: x-long shaft V6 Merc on long shaft transom

cant the shaft come apart like a smaller ob? is the xlong part removable?

 

[DJ]

Re: x-long shaft V6 Merc on long shaft transom

WWYC has a good point. I do not know on that model.<br /><br />A a minimum, you would need a new driveshaft and to reseal the lower unit, after installation.

 

[kcrafton]

Re: x-long shaft V6 Merc on long shaft transom

I am not opposed to investing further in this motor to convert it to a long shaft but I don't know where I can find a drive shaft and drive shaft housing at a reasonable price. One guy I talked to said the drive shaft from the dealer would be $700. Add the housing and the labor to do it makes it a tough swallow. But the motor is priced right and if I could find the parts "used" it could be worth it. Anybody know where there are some 2.5 liter Optimax mid-sections lying around?

 

[DJ]

Re: x-long shaft V6 Merc on long shaft transom

Check with these guys.<br /><br /><br />www.twincityoutboard.com

 

[kcrafton]

Re: x-long shaft V6 Merc on long shaft transom

Thanks DJ. It would make my day to pull this off.

 

[mattsaks]

Re: x-long shaft V6 Merc on long shaft transom

i am a bit suprised to hear about instability while planing... the guys over here (new zealand) with the big race boats are jacking their motors up so high that you wouldnt think they run! apparently its the fastest and most efficient way. i will be raising my transom to take an xl shaft 90hp tohatsu. it has to be better than my 32 year old 65 johnson!!