Mercury Optimax help please!

I've posted this on 2 other forums, so please excuse if you see this again.. just trying to get some quick help.

2008 Optimax Pro XS 225 with 480hrs.

I just got a prop out of the shop and took the boat to test it out today. Started right up like usual, ran it for a few hours most of the time at WOT since speed is what this prop is supposed to accomplish. Not a hiccup, turned full RPM, ran perfect.

Anyway, go to power load on the trailer. Hammer down, and motor bogs down and wont go over about 1500rpm. Literally doesnt have the power to push the boat on the trailer. So I take it back off the trailer.... Go to run it again, and sure enough, jumps right out of the hole and once again runs wide open no problem. Go to get back on the trailer, same problem. Wont go over 1500rpm. Take back off trailer, run it even longer, screams like a new motor, then same thing happens when trying to power on the trailer. Weirdest thing I've ever seen!

Only thing I've done diagnostic wise (and I BELEIVE this might be the issue, but want to double check): I put my coil tester on and tested all 6 coils.. The #5 coil doesnt light up as bright as all the others, so I assume this may be my issue. However, the reason I ask is because I've already replaced 2 coils, but when those went bad, they didnt light up at all and the boat wouldn't even get on plane. #5 coil still lights up, but is much dimmer than the others.

Fuel filter is only a few weeks old.

Taking the boat out of town this Thursday which is why I'm trying to get some quick input before I buy a coil.

Any other ideas throw em at me. Thanks everyone

Are you trimmed up when you power load? Running at wide open throttle is trimmed down so assume you're trimmed up quite a ways when loading? Maybe has something to do with that? Fuel line kink trimmed up?

Yes sir trimmed up.. That's why the prop was in the shop in the first place, a boat ramp got it.. lol. I didnt think of that, could be possibly. But at the same time, when I'm on plane running WOT I'm trimmed up the same amount as I am loading up.

Well, then that ain't it. That's pretty crazy man.

You're telling me!

Like I said, one of the coils isnt lighting up as bright as the rest, so that's my assumption. But again, I'm getting assurance because the past two I replaced didnt light up at all and the boat wouldn't even plane

Did you change the number of pvs plugs? Might be getting too much bite now.

I didnt change anything on the prop. Literally just got it repaired (rounded the tips of the blades off.) Been running my back up prop for a while (3 blade 25p Fury.) Prop that got repaired and is the main prop is a Turbo OT4 23p 4 blade. It ran fine on this boat to begin with, but I was also thinking that maybe the prop is biting too much?? That doesnt make sense though considering like I said, it runs perfectly fine on the water

I'm going to take the back up 3 blade to the ramp tomorrow to see what happens. I've seen crazier things....

But does anyone think my current diagnosis on that coil may sound right?

But on the water the boat has some give, when on the trailer, it has no give and the motor wants to stall out. Now I don’t know why it would be different than before, that part is odd.


I have no clue on the coil, I don’t think it would run properly if that were the case; but I’m not a mechanic. Best place to ask would be on BBC, Merc boards. Some smart merc fellas there.

Thanks for yalls help!"

How much fuel is in boat? Any chance that when the boat is going up the incline of the ramp it is sucking air. I have seen that before. All the fuel would run to back of tank and the pickup tube was slightly ahead of center.

Alright well figured out the problem

Anyone who said it's a propping issue, beers for you.

Went down to my local ramp... backed it in with the 4 blade (the one I had fixed) and it was doing the same thing I mentioned. Wouldn't go over 1700rpm on the trailer.

Pulled out, threw my old 3 blade on, and I'll be god danged if it screamed like a new motor.

I repeated this process 6 times just to make sure it was the issue. Sure enough, everything runs perfectly fine with my 3 blade.

So now that we know this, heres the only I can think of.. is it possible that the prop is slipping on the shaft? My guess is when the motor feels that it's not under a load and not pushing, it wont rev over 1500rpm.. so the only thing I could guess is that the inside of the 4 blade is worn out and not getting a grip on the shaft

Like Grout-Stout Stated. Vent plugs. I run a 25 Fury on my Triton and have all holes plugged. Just to get it to load.

If the prop was slipping in the hub rpms would be very high, not low. Different props act very differently, higher speed props usually have less power for loading although I am a bit surprised you still have a good holeshot with it. Also it is a 24p compared to the 23p so it has less power there also. I have had a few setups that ran great on the water but did not power load well, usually had to back the trailer further down the ramp to load them...

You might have a coil issue as well. My 08 250 had a factory recall on the coils. Sounds like that’s not the culprit but may be something to take care of anyways.

Raise your jackplate up and get the motor out of the water. Mine did the same thing once and that fixed it.

If your motor is running good as you have stated then it’s fine.

Mine used to do it on steep ramps and the lower cowling was under the water

Just to clear things up

The 4 blade prop mentioned that is giving me trouble, I ran that prop on that boat since I got the boat in 2015. Never had a problem loading up or anything. I messed it up on a ramp so started running my 3 blade for a while until I got the other fixed. Now that it's fixed, I'm having this issue. So why did it run fine on the 4 blade for 4 years, but now all of a sudden wont push the boat on the trailer?

Also by the way, the boat runs faster with that 4 blade. I get 64 WOT on the 4 blade, about 58 WOT on the 3 blade. It's not a bass boat, it's a center console bay boat.

And again, it's not a motor problem. It runs perfect with the 3 blade on the water, loading up, everything. Soon as I put the 4 blade back on, wont push the boat on.

I'm not a prop expert, but on this particular prop theres no holes to plug it dont look like. It's a Turbo OT4 prop.

I have an 08 opti. As well. If my motor is trimmed up off the hydraulic pistons it will not rev over 1500 rpms and give a short 1 beep alarm.

A bay boat with a 250 that will run 64 WOT with a 4 blade........will push itself on a trailer with a TWO BLADE!

Not a typical bay boat, lol.. Majek Extreme. They are built for performance. It'll keep up no problem with any Ranger with a 250. 64mph WOT GPS.

And whether y'all realize it or not, there is a bay boat builder down here in south Texas called Simmons Custom Boats.. 22-25ft center consoles. They run 95mph+ all day no problem... lol. The 25ft version of my boat with the 300 runs lower 70's. Not all bay boats are slow pigs. You'd be surprised the looks on Ranger drivers faces on Sam Rayburn when I pass them up haha. The holeshot on these Extreme's will jump any bass boat any day.. I've beat my friend with a 20ft Blazer/250 HPDI out of the hole, and the Stratos/225 Rude we used to own. Obviously both took me on the top end, but not holeshot.

Anyway, I still haven't figured out why it won't go up the trailer with the 4 blade, cause I ran that same prop for 4 years. But I'm heading out of town with it tommorow so I put the 3 blade back on and called it good. I'll try and see whats up when I get back.

Only thing I can figure, is that the prop man changed the pitch of the prop when he fixed it. Nothing else really makes much sense.

This ^^^^^^^ or prop pitch was changed.

It may seem simple but just put the trailer deeper in the water. The angle of the ramp will also make a huge difference in loading.
rd

Man you really have a hard on for Ranger. I’ve read multiple posts of yours in the last few months of you saying Ranger sucks and comparing your superior boat to other Rangers. Ranger is just a boat maker not an ex gf to be jealous about.

My Ranger 521/250 Pro XS isn't anything unique for the combo, but it does more than 64! ...typically 71-72 mph.

I glad you have it figured out when I read it I knew it was probably the prop my old 2009 250 pro xs did this with a 4 blade prop.

Ha! That Ranger sucks comment is just to stir the pot on those threads.

And by the way, I know this rig isnt gonna leave a bass boat in its tracks.... I'd love to get back in to a bass boat, but I live 15 mins from Galveston so it makes more sense to have boat that will go to the bay and the lakes. I'm not try to chit on Ranger or any bass boat cause I love them, just trying to get my point across that this particular bay boat isnt some heavy slow pig

Interesting, never been in a Ranger so I wouldn't know.. my understanding was to expect mid 60's in a full size Ranger from things I've read on here. My mistake!

I called the shop that did the work on it, and he was at a loss on what it could be.. (I took it to a very reputable shop here in Houston (Baumann Propeller)... Great people!) He gave me the number to a guy that knows these Optimaxs up and down, and he told me that what I'm experiencing is very common when a 4 blade is put on these motors. What I'm still not understanding though is, why did I run this prop for 4 years with never a lick of issues loading up on the trailer, but now all of a sudden it wont go over 1500rpm?

However, every ranger ive ever had or been on loads on a trailer with no problem!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

maybe you should have got a 250 pro xs so it had enough power to load!

Here is your answer😉

I run a Trophy 4 blade on my 250 and have never had this problem. I think you're trimming your motor too high.

what an ignorant comment. Some people fail to read when I state that I've ran that 4 blade for 4 years, and never had a problem until prop man repaired it. I have no issue whatsoever pushing on the trailer with the 3 blade. And once AGAIN, never had a single issue with the 4 blade until it was repaired this week. If you are that offended by my Ranger comment then I'm sorry... I'll consider a Ranger when it can get up on plane in a foot of water and still maintain mid 60s when needed/wanted.

Thank you folks that are giving me genuine replies.. grout, that's the only thing I can figure too.. i called him like I said and he claims the prop was set back to how it was originally.

I actually took video of my tests I did yesterday to show prop man.. I'd gladly put them on YouTube for you folks to see

Too high? Everyone is telling me to trim up as far as I can and see if that fixes it.

When I get the chance I'll post the vids I took yesterday and put a link here. I'm heading out of town to Port O Connor with it in a few hours

Heres some pics of the 2 props if helps with a visual

Also a pic of where I run the motor loading up. Jack plate on 5, trimmed up on the 2 cylinders

You do want the thrust pushing as close to parallel to the keel of the boat as possible. That way, you are pushing the hull up the bunks, not pushing the stern down onto the bunks, where it will lock down and not move up onto the trailer. I've had this occur with a bass boat, but didn't have the engine bogging down part.

Given there is no harm in trying, I suggest you put the trim where the propshaft is parallel with the keel of the boat. (I know this makes the prop draft a bit more, but you'll get the best forward thrust.) Next, run that jackplate up as high as necessary for it to clear the ramp. You should be able to get an idea of what this is with the boat sitting on the trailer. If the trim is level to the keel, will the jackplate get you out of danger of a prop strike? If so, try that setup for loading. One thing I'm also trying to do with this suggestion is get away from a sensor that trips into "limited RPM mode". Maybe the trim you end up using with the 4 blade is close enough that it tricks the motor into limiting RPM.

I love the bungee cord around your power pole!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

you don't have enough motor to load your boat, your power pole is broke buuuuuuuuuuuuuut your rig is better then a ranger!!!!!

i love this thread

Sounds like a venting issue to me. I had a Champion 202 that was the exact same way with a Trophy 4 blade.

I'd take a Majek over a Ranger every day of the week and then 3-4 times on a Sunday.

Its the new prop and the number of plugs in it or probably not in in your case.

My power pole works perfectly fine, I put a bungee cord on because I've heard of accidental deployment going down tthe road

And it has plenty of power.. I'll post a video when I get home. It's a prop issue!!!!!! You are ignorant as they come sir

And it has plenty of power.. I'll post a video when I get home. It's a prop issue!!!!!! You are ignorant as they come sir