Help with an 08 225 Mercury Optimax

[DrawDown]

I recently purchased a used 2008 225 Mercury optimax to repower my 21ft Kenner Vision. Boat was underpowered with a 135. Anyways, prior to purchasing it, the gentleman had it looked through at Chris' Marine (which I was present for). No problems, no fault codes, good compression. Plugs and filters fresh. It was on a 24' Kenner which I rode in prior to them removing the motor. Ran great. Good hole shot, good top end etc. it was running a 19 pitch Rev 4 prop with all the plugs removed. Bought the motor, got it home and had Capt Kirks install it along with a 6" Bobs action jack, and a water pressure gauge. They did a really good job. I wanted a Rev 4 prop since i was pretty happy the way it performed. I figured since my 21ft Kenner is about 4-500 pounds lighter than the 24ft it came off, I'd go up to a 21 pitch. Got it back, put the prop on (new) with a new hub kit, fill it up with gas and take it to the lake today to test it out. Motor fires up first crank and idles nice. Handles good around dock with that prop. Buddy says well lets see what it'll do. Rolling at just under 1000 rpm I hammer it. Uhhhh, wow not what I expected lol. Best I can describe is the motor climbs very slowly in rpm, like it's lugging I guess. When it hits around 2500 rpm, hold on son cuz its a rocket ship. That is coincidently about the rpm it planed at. Motor runs fine once past that point at any rpm and will hold that plane real slow. I tried all different jack plate settings and trim settings. Same thing. I thought maybe it's over propped, but it's running 58-60 at 55-5700 rpm, so I mean it's right where it needs to be. I tried removing all the plugs from my prop and it did the same thing but blew out as soon as it got on plane. Motor is still under an extended warranty so I'm covered, but thought I would get y'alls opinions if it's the prop or something more severe. I also have the 19 pitch Vengeance from the 135 I can try too. Any thoughts? Sorry for this being so long.

[Revolution141]

Just the prop mate. Was the plugs you had in full blanks? Try a plug with a medium size hole (or drill out solid plugs gradually getting bigger until you find happy medium).
From what you described the prop isn't aerating enough. Then when you removed plugs its just blowing out completely. Bear in mind these motors are not rocket ships on the plane(unless your way overpowered), rather they pull onto plane. I have a 300xs on a 21' ski race boat and it doesn't even launch so don't be concerned.
Also the setback of the jack plate will result in slower plane. If you have tabs try planing with tabs in as this will force nose down and result in quicker planing. Once your on the plane, as you said, she's a rocket.

[DrawDown]

I do have tabs and will try that. The plugs in the prop were the solid ones which are what I pulled out. I will say this, the 135 that came off the boat planed the boat MUCH quicker. I thought it would've been the oposite considering the 225 is up 90 horsepower and it is a larger 3.0 compared to the 135's 2.5

[gregpro50]

Is the motor firing on all 6?

I had an issue with my optimax where it was coming on plane like a freight train going up hill. Once it got on plane it would still rev out to 5500 or so.

I started unplugging the coils until I found a cyl that wasn't firing. Turns out I had a bad spark plug. I replaced the plug and the boat would almost jump out of the water and hit the 6300 rpm rev limiter easy.

The funny thing is that the motor still started and idled nice on 5 cyls. It even seemed to run pretty smooth.

[DrawDown]

When the motor was checked out right before I picked it up, I saw the mechanic cut spark to each cylinder using the diagnostic tool and each one cut spark then went back to normal as it should've, so im assuming that it's firing on all 6. Im pretty mechanically inclined when it comes to car engines, but havent done much on outboards. Is unplugging coils one by one the best way to check? Does this sound like it could be a coil? I really appreciate everyones help.

[gregpro50]

Unplugging coils is the easiest way and you won't get zapped like if you pull the wires off the plug.

These motors are known for having coils fail.

Mine ran perfect for a week after I got it and then a plug went bad...

Might as well give it a shot since it is pretty easy. Just un plug them one by one when it is running. You will hear a significant difference when you do it. If it makes no difference then no spark on that cyl.

[ar300johnson]

If your boat won't plane quickly, your prop is not ventilating enough. If your plugs are completely removed, you may need another row of PVS holes. On both my 4 and 5 blade Hydromotives, I have 2 rows of Pvs holes. I add or subtract plugs untill my props spins up to @ 4000 RPM and my boat easily gets on plane regardless of fuel load or number of passengers. Any reputable prop shop can do this for a reasonable price. It sounds like your full throttle RPM is about right and on plane performance is good. Get some more ventilation and it sounds like your prop will be good.

[sashweer15]

Nice discussions going.... keep on posting... very useful information are there....:-)

[gen2flight]

Enormous blade area on the rev 4, they are the slowest props I've tried in initial holeshot regardless of pitch, vent plugs removed ect. The 17" rev4 was as big a pig out of the hole as the 21 I tried although like you have said, once you are rolling they pull hard. Try a trophy plus in a similar pitch and you will end up with completely different result especially a faster holeshot with a higher initial rpm, much more in line with the torque curve of your 2 stroke.The trophy will perform better at the higher engine heights as well and will fix that holesot/acceleration issue right up. prop changes will fix your problems that rev4 is a better verado prop.

[stokernick]

just had an issue with my Optimax,and it was a bad coil,subject to recall,replacing all 6 under warranty[nice,since they're $121. a piece!!]