What can you tell from this wake?

[JustPhish]

OK this may be odd but I figure there has to be someone on here that can do something with this. Last season I was having a problem with my trim tabs. They were barely moving and my fuel consumption seemed to be ridiculous. This season I topped off the resevoir for the hydraulic pump and now the tabs move, barely breaking the plane of the hull of my boat. I called Bennett and they said that I should only be getting 2.5" of movement out of the cylinders. It appears I am getting that.

So now I see a much better improvement on my fuel consumption this year so far but I am curious if I am trimming my boat properly. Can anything be gathered from this video?

Boat is a 29' 82 Chris Craft 281 Catalina
Engines are 2 x 350 Merc crusiers? inboard
RPM at the time was 2800 for both engines and speed was around 17.5knots (I still am unsure what RPM is optimum for these engines and thinking my boat should really be going faster). Loaded with only me, my wife and two small children that were below deck.

Hmm, when I look at thread I only hear audio and see no video so I am including a link to the video on YouTube just in case

http://www.youtube.com/watch?v=zPQEGwBQjb0&feature=plcp

 

[shrew]

Re: What can you tell from this wake?

The max RPM range for the Mercruiser 5.7L should be between 4400-4800. That is MAX rpm range, which is where you should be at Wide Open Throttle (WOT). This is not necessarily the optimal rpm range. What are your RPM's at WOT?

 

[UncleWillie]

Re: What can you tell from this wake?

It looks like you are too Bow Down (Over Trimmed).
But Hard to tell from the Video.

Get another video looking over the transom at the tabs.
Are they skimming the surface or do you have "Drag Brakes" with the tabs buried under the water?

 

[Ned L]

Re: What can you tell from this wake?

2800 RPM, 17.5 knts, wake looks nice to me, I'm thinking it all seems pretty good.

 

[JustPhish]

Re: What can you tell from this wake?

The max RPM range for the Mercruiser 5.7L should be between 4400-4800. That is MAX rpm range, which is where you should be at Wide Open Throttle (WOT). This is not necessarily the optimal rpm range. What are your RPM's at WOT?

I've never had the throttles all the way forward because I was worried about redlining the engines. I think the max I have put them up was maybe 3200rpm. I have never seen the second set of barrels in in my carburetors open.

 

[JustPhish]

Re: What can you tell from this wake?

It looks like you are too Bow Down (Over Trimmed).
But Hard to tell from the Video.

Get another video looking over the transom at the tabs.
Are they skimming the surface or do you have "Drag Brakes" with the tabs buried under the water?

I'm not sure I could get much of a view of anything with my tabs under my swim platform but here's what they looked like when I got them fully extended down after working on them. When I was trimming I just kept an eye on my speed. When my speed started to drop back down after peaking, I brought the bow back up a little bit until the speed got back up to peak.

 

[JustPhish]

Re: What can you tell from this wake?

Thanks for the input Ned. I am in CT as well, my boat is docked in the Housatonic. Do any boating my way?

 

[Ned L]

Re: What can you tell from this wake?

It sounds like you have a pretty good understanding of adjusting them. --- Sorry to say I'm in the other end of the state (N.E. corner), and only pass thought that area when I go back to the Jersey shore where I grew up.

 

[UncleWillie]

Re: What can you tell from this wake?

... here's what they looked like when I got them fully extended down
View attachment 153900

Definitely NOT drag brakes!
That looks almost like the UP position.

You need to open it up to see if you have a problem.
4500 rpm will sound like something you have never heard. But it is OK!
Running up to 4800 is not going make it blow up.
If it goes above 5000 just back it down a little.

Just be prepared the see the fuel gage moving.

 

[Philster]

Re: What can you tell from this wake?

Ned: Where'd ya grow up along the Jersey shore?



JustPhish:

The wake looks good. Doesn't mean that much though. What I did see above the wake was steam. I want to ask about the age of the exhaust components and was going to ask about whether she's a saltwater boat, but now know she is.

So, wake ok... but I feel compelled to mention the steam.

 

[JustPhish]

Re: What can you tell from this wake?

Ned: Where'd ya grow up along the Jersey shore?



JustPhish:

The wake looks good. Doesn't mean that much though. What I did see above the wake was steam. I want to ask about the age of the exhaust components and was going to ask about whether she's a saltwater boat, but now know she is.

So, wake ok... but I feel compelled to mention the steam.

What should I be concerned about with the steam? One thing I notice this year which wasn't so obvius last year is when swimming and I approach the platform I get a strong smell of fuel. That was only the second time I took the boat out since being winterized and the first time I opened it up that much since last season.

 

[wutleak]

Re: What can you tell from this wake?

New to this site and low rank but here's my two cents.

You want to make sure your entire power train is working properly and configured correctly. you also want to get an adea of what you boat, based on your configuration should do. I have found this site helpfull http://vicprop.com/calculator.htm.

then you can start to look for the problem. max rpms for your engine is 4400. best operating rpm (generaly) is 75 to 85 % of max RPM. if prop and drive are working properly you may want to look at your engine(s). and, if engine and drive are working properly it may be the prop, and so on.

I would make sure these items are in order before attacking the rest of the boat. you may find your boat is already working as it should.

wutleak out.

 

[Ned L]

Re: What can you tell from this wake?

I grew up boating on the Shrewsbury & Navesink Rivers, and Sandy Hook Bay. I don't think I'd be concerned about that much steam if your temp gauges read fine. Are your engiens raw water or fresh water cooled?

 

[UncleWillie]

Re: What can you tell from this wake?

I've never had the throttles all the way forward because I was worried about redlining the engines. I think the max I have put them up was maybe 3200rpm. I have never seen the second set of barrels in in my carburetors open.

Optimum cruise RPM (Max Miles/Gal) typically falls between 3000 and 3500 RPM for most boats.
Go faster you may find you also go cheaper!

 

[JustPhish]

Re: What can you tell from this wake?

I grew up boating on the Shrewsbury & Navesink Rivers, and Sandy Hook Bay. I don't think I'd be concerned about that much steam if your temp gauges read fine. Are your engiens raw water or fresh water cooled?

I want to say my gauges barely go past a quarter of the way and are at 140? I think? I'll have to pay attention tomorrow. They are usually pretty close to the same between port and starboard. They're cooled with raw water I guess. Ioften am out in the sound but it's docked in pretty much freshwater as far up the river as I can go. That spot right there where the video was taken was right at the metro north bridge in Stratford/Milford so mostly saltwater. Last night when I docked around midnight with absolutely no breeze it did look like a ton of steam coming out and lingering.

 

[UncleWillie]

Re: What can you tell from this wake?

... when swimming and I approach the platform I get a strong smell of fuel...

Please don't tell us you have swimmers in the water with the engines running!

 

[JustPhish]

Re: What can you tell from this wake?

Optimum cruise RPM (Max Miles/Gal) typically falls between 3000 and 3500 RPM for most boats.
Go faster you may find you also go cheaper!

Thanks Uncle Willie, I did notice a big difference this year like I said with the consumption already. Last season a trip down the river would cost me almost a quarter tank of fuel on a 120 gal tank and then another quarter on the way back home. This year I have been up and down twice, (two down, two up) and I have JUST used a quarter tank last night. And that was only because I was only moving at 8-9knots because of navigation and the engines were around 2200 rpm. I can see the difference in going slower and plowing through the water and revving up the engines but sitting on top of the water. I'll give 3500 a shot tomorrow when I am in the sound.

 

[JustPhish]

Re: What can you tell from this wake?

Please don't tell us you have swimmers in the water with the engines running!

Come on! Who does that? It's not a pleasure craft/salad shooter. The exhausts are right on either side of the swim platform. When I get back on the boat and pass the exhausts I can smell fuel.

 

[Philster]

Re: What can you tell from this wake?

Steam can indicate manifold/riser issues (internal leaking). In salt water, the have a service life of about 5 years and it can be as short as 3 years.

The number one cause of marine engine failure is water intrusion from leaking exhaust systems.

(could also be a head/gasket leak)

.

 

[UncleWillie]

Re: What can you tell from this wake?

Come on! Who does that? It's not a pleasure craft/salad shooter. The exhausts are right on either side of the swim platform. When I get back on the boat and pass the exhausts I can smell fuel.

I feel better Now!

If your exhausts are the above the Waterline/Transom exhausts, your hot exhaust gasses are blowing through the cooling water on the way out the exhaust.
Steam is to be expected, especially on a humid or cool day.