rpms accelerate in rough water, lose of speed

[dpatwelk]

Hello,

I have a 2012 4 stroke 175 hp Suzuki. The motor is on a Glasstream 2012 22ft center console.

I have noticed when I'm in rough water I will be on plane and experience a surge in rpms and loose speed. The rpms will stay high and the speed continues to drop until I throttle down. When I throttle down and essentially start over I will get back on plane until the incident happens again. I have never had an issue when the water is calm or has a moderate chop. This started happening over the summer.

The only solution I have found is to go super slow in rough waters. Last week it took me almost two hours to run 22 miles in two foot seas.

Any suggestions...

[Solarman]

df175, 2012, RPMs & speed problem

Sounds like your prop is slipping. Two years old is quite new for it to start slipping from age, or use. It may have started slipping if you hit a sand/ mud bank. It can be rebuilt, but you may need to check with your dealer for nearest prop repair shop. Or, google it for your zip.
Good luck.

[artdf175]

one other thing to double check .. height of motor ..
if mounted too high it could be trapping air in the prop and not digging back into the water ..
my engine was mounted about one hole setting too high
I was not having a noticeable problem.. but upon having it put at the proper level - made a huge difference in performance ..
Art

[Moonlighter]

Have you added anything to the hull at around the time the problem started to occur, for example, any thru-hull fittings such as a transducer in the hull ahead of the engine?

Anything that has changed the water flow under the hull towards the motor may have affected the grip of the prop on the water. Even shifting load in the boat towards the bow may have shifted the balance point of the boat and lifted the stern higher.

Also, as others have suggested, any damage to the prop, however slight, can cause these sorts of issues. Getting it fixed is not too much of an issue. A stainless prop will also grip better than any alloy prop.

Also, if you changed prop from one size, or one brand, to another, can cause these issues.

[BillCon]

Sounds like your prop is ventilating, similar to cavitation but different, I, can make mine do that in 2-3 ft waves also, even running a 24" SS 3 blade prop when I, trim all the way up and trim tabs down, you may have to lower your motor an inch or even two.

[Harper2]

My vote is for prop ventilation.........

[dpatwelk]

Feedback

My takeaway is the motor shouldn't be doing that. My boat is very light compared to most boats its size. Could that be bringing the boat out of the water more in rough water? I have a stainless steal prop and run in clean water.

Thanks,

[Harper2]

Well, in rougher water, it's not that your motor shouldn't be doing that, it WILL do that if you make it do it. The point is that if it's not doing it in smoother water on plane, then you probably don't have a problem, and in rougher waters, when the bow drops off a wave, you're lifting the stern and the prop out of the water column enough to cause it to ventilate, i.e., catch air, lose grip on the water, therefore lose thrust, increase RPMs and lose speed. Then as the next wave approaches, and the bow lifts, you regain "traction" ......until you top that wave, at which time, it starts all over.

[dpatwelk]

Thanks for the reply. What seems to puzzle me is it hasn't always done it in rough water. It use to not do it.

[Harper2]

Well, I can't specifically answer your "hasn't always done it" comment, but your Glasstream is similar to my boat. Yours is a couple feet longer, 150 lbs heavier, holds 9 gallons more fuel, and I think mine is a little deeper "V". I have a DF150 and it will do what I outline in the previous post in the gulf with 4-6' rollers if I try to run too fast, or in 2-3' chop on plane, it will occasionally catch air. Have you done anything lately to add weight to the bow, such as a trolling motor and more forward-mounted batteries? If your hull is clean and you haven't added any thru-hull fixtures as Moonlighter has suggested, and haven't damaged the prop at all, about all that's left to consider is adjusting the trim downward a bit more than you have been running in those conditions in which you find it occuring.

[Solarman]

df175, 12, cavitation problem

Dpatwelk, you can check prop to see if slipping by marking the hub, and prop nut. If your marks change alignment, it's slipping then repair/ replace.
If your boat weight has changed, added heavy cooler to bow area, or something like that, then this could also change how your boat runs in higher seas.
We can only offer you suggestions of those things that can cause your problems. Everyone here is trying to help you understand your situation. You are the one that best knows your boat, and if anything has changed, or is different.
Good luck, and let us know of you find out what is causing your problem.

[dpatwelk]

Thanks, Mike.

Adding weight upfront would likely help. 2-3 chop is prob when its the worst. I talked about adding a trolling motor and the batteries for that would be upfront too.

I will check into the moonlight.

[Solarman]

cavitation problems

Actually, it seems that less weight up front might be better for your problem. The more weight in the bow will raise motor higher, and cause more problems.
If adding a trolling motor to bow, mount the batteries in the stern, as far back as able. Not in bow, or the console.
Good luck.

[Harper2]

Thanks, Mike.

Adding weight upfront would likely help. 2-3 chop is prob when its the worst. I talked about adding a trolling motor and the batteries for that would be upfront too.

I will check into the moonlight.

You misunderstood my question. I asked if you had added addition weight in the front recently, thinking that if you did, it might have coincided with when you say the problem started. Adding weight now will likely exascerbate the problem.

[BillCon]

I, have a DT150 on an 18 HydraSports and I, can slip a 24' prop in a heartbeat, in rough water with just a 1 second bump of the trim switch up past smooth running. my point is the slightest change in weight distribution or trim can make a big difference, I, can put on my 22" 4 blade and it grips like velcro, drop the motor an inch and it should stop