Buying an optimax for my boat

[loxboy1]

Hi all, I have a 2002 opti 225 xxl (30inch shaft) on my center console. I put a rod through the block. I dont have alot of money so im just going to replace it with another used one.

I found one but its a 25inch shaft, can i just take the lower and extention peice off mine and put it on the 25inch motor making it a 30??

Also my boat is somwhat custom in the the orig owner gutted this answer hull and redid it from the ground up and enclosed the transom and added a bracket. It has always had the 30inch motor and runs good 55mph, how can i tell if i need the 30inch shaft or if i can just keep the 25inch the way it is.

Also i dont have a computer to check the other motor when i go to look at it, is this a bad idea? I will however be starting it and performing a compression test.

Please let me know as im scheduled to go look at it some time tomorrow.

Thankyou

 

[Chris1956]

I am not sure how you are going to test that motor w/o the computer. A water test would be good, as they can idle real well and not rev up.

As for using the 25" motor, you need to see where the current motor is mounted, and where the antiventilation plate is in relation the the bottom of the hull.

I converted a XL shaft Merc to LS, by removing the water tube extension, spacer, using the LS gearcase and changing out the XL studs. That was on a '93 V6 motor. Not sure if the newer Mercs are the same. It would best to measure the midsection on both motors.

 

[Texasmark]

I never did it but my thoughts. Before you buy it consider you will need the old midsection outer casting, assume exhaust tuning horns would be identical, and water pickup tube. On the lower unit you would have to change out the drive shaft (might as well do your water pump and upper LU seals while in there) to the longer one which means popping the rear bearing retainer, pulling out R gear and bearing to access the nut at the bottom of the drive shaft inside the LU (while there might as well put in a new prop shaft seal. When you get your old shaft installed you have to check clearances which are listed in the manual and will need (as the manual states) an alignment tool to determine if you need any shims on any of the gear hook ups....pinion on drive mesh with F and R gears. Since you did the other two, might as well redo your shift shaft seal and new gaskets for your drain and vent plugs.

If you buy the engine with conviction that you will do the above if necessary I totally agree with Chris to check it out on the water with the 25 first. You didn't mention the size/weight/hull shape of your boat. 55 is fast for a boat, but a lot smaller engines produce that. Point here is that you may have had your LU too far in the water creating excess drag with your 30" With the bracket you have "setback" and the "old guns" on here used to have a number for that....in short you have to jack the engine up the farther you set it back due to how the water rises after the transom passes.

I suppost what Chris said about the AV plate but I don't agree with using the bottom of the hull for your metric. Get on the water and if it will, with best trim, maxed out at engine top rated rpms and have a look at where your AV plate is riding with respect to the surface of the water passing it. If it's at or just below that water level then you are good to go and if the engine is running like it should you should be on up in the 60 range due to the reduced lower unit drag.....then check the WOT engine rpms vs what you had with your current prop and if the new LU came with it's own, with that prop.

Course another alternative is moving the bracket or the engine mounting plate to get the correct distance back. If you decide to drop the plate following seas may get up around your powerhead. Course they are sealed pretty good but still, you may get a slight dunking. Air enters the top rear (I guess) so your performance shouldn't be effected I wouldn't think.

Check back.

 

[loxboy1]

Thanks for the replys guys. I picked up a 225 opti 25inch shaft. Bolted it on and took the boat for a spin. Wouldnt plane with the 25inch shaft. At 4000rpms is the hightes i could go otherwise the prop would cavitate. My hull has a deep V. I had the 30 inch lowerunit and 5inch midsection extention plate off my orig motor, bought a shift rod and water tube extention installed it all then whent out the following weekend, planes off fine and water is under the av plate like suppsed to.

 

[Texasmark]

Great