motor height on a 265? can't find orig. post

[jekyl]

Sorry but I can't find my original post in which i asked this question.
Rich (JUST IN TIME) asked for pics as I was about to lift my motors; 200hpdi's, 1 hole and he was concerned that it would lose grip. In the pics the motors are on their current setting with only one more hole left to the highest position.

I have done 5 trips( approx 290 n. miles) so far in very fair conditions with no real problems. I have yet to use them in rough conditions which is obviously when problems are most likely to occur.

Just looking at the fuel management gauge I would appear to have a saving of around 5 litres per hour at cruise (4,000 rpm). Around 7% improvement.

I decided to go down this route as on the merc site it said it was pointless changing props until the ones you had were operating at their optimum efficiency ie. setup at the right height, and that the top of the cav plates should be just visible. Well see for yourself but mine are still just under.........I don't think I would go any higher, there does appear to be a slight "burning" on the back of the blades and I'm wondering if that is slippage? Tanami is slightly slower onto the plane (but that was never an issue anyway) and certainly if trimmed too high will overrev more easily.

I will take all opinions on board as i have not had enough time to make up my mind yet. Certainly at times she seems the best she has ever been.Coming home from 50 miles out on Sunday we still had 200litres on board, 5 crew and a kill tank full of NQ Spanish mackeral (much different to yours i think) I we were doing 4,300rpm and 31.6 knots on both GPS'.

I am not 100% convinced until I have had her out in more challenging conditions. And I have yet to go to WOT to see if i have picked up the additional revs i was looking for.

 

[gradyfish22]

If you upgrade props you will surely add rpm's, right now you have either aluminum props or painted SS, either way a polished SS prop will pick up rpm and be more efficieny, the smoother the surface the better typically, assuming it is the right size. As you state, before you waste time looking for a prop, get the right prop height. I will be in Wed, if I remember I will take a peak at my trim plate height, to be honest I haven;t paid much attention to it since she turns up nicely for me, but it is something I should look at too, maybe burn a little less fuel if it is not correct height. Not sure what the proper mounting hole for the HPDI or F225 was honestly. If you have seen a gain your heading in the right direction it seems, as far as rough seas, that can make a little difference, but if you turn her hard over on plane and she does not cavitate bad you should be ok, but until your in the rough stuff there is no 100% surefire way to tell until the real thing.

 

[jekyl]

Thanks Tom I would appreciate any advice or info.

I am especially interested if anyone has seen this burning on the back of the blades? I seem to recall seeing pics somewhere else and they stated that it was due to prop slip?

Or am i just being too sensitive ?????

 

[gradyfish22]

It is true that over time a prop will slip and cause some cavitation depending on how good of a prop selection and material it is. I know Yamaha props hold up ok, but do see some wear over time, mine are in good shape, but not as nice as I'd like to see them, seems merc props have a better finish on them and last longer from my research. The small holes on the back end of your prop are without a doubt caused by caviation, it could be from a thru hull below the waterline and forward of the engines, a transducer, or just prop slip or prop height, but you do have cavitation occuring from the look of your prop. Not positive what is causing the burning mark, have not seen much of that, I will look into that a little more for you though.

I do not feel your over analyzing anything, if I saw that on my prop I would surely wonder what was causing it as well and wonder how it is effecting my performance and such as well. As far as the height of the motor, you are doing the right thing noticing you might not be performing how you wish and playing around with it to get it better, and from your findings so far it seems like your assumptions are proving true and the new higher hole position is running better. A lot of owners are not conscience of these items and ignore them or do not think of them. It is good to know your boat and know if something is not ideal and to make it better, it will benefit you and also shows you care about your craft.

 

[JUST-IN-TIME]

they look right on
you can see the red stripe on them

the true way is install a water pressure gauge
look what they run now
then look what they run next hole up

if your fully trimmed out, it looks good

 

[KingJ]

That's how my HPDI runs, with the red stripe showing. Our aluminum prop shows a wear-streak mid-blade (at about 300 hrs)., and our trusted mech says this is quite normal. Hope this can help some.

Cheers,
Jim

 

[jekyl]

Thanks for the replies guys. I am waiting for some bad weather to arrive while i'm out in it to confirm the height is ok.

 

[fishingFINattic]

Maybe I missed it, but what hole are you running in now and what did it come with?
Mine has never been changed and set in the lowest holes possible.

Tim

 

[twinyams265]

My hpdi's were mounted at the lowest hole as well. When I was getting ready to swap mototrs (newer hpdi's), I called Grady and they told me to definitely mount them at the lowest hole and that the hull was designed to run as such.

 

[jekyl]

At the top of the page i have detailed it is now 1 hole from the top and before that was 2 holes from the highest position.
Whilst I respect Grady's advice, the position which is going to cause least issues for the most folks, is probably also the lowest. However if you are looking for efficiency gains and know your usage and current requirements then there is generally room for improvement.
The analogy i would use is just because my 4x4 tyre manufacturer says to run at 35 psi doesn't mean I will run them at that pressure when at 45psi I can get up to 20% more durability and less rolling resistance thereby less fuel usage and for the type of driving i do have no negative performance characteristics.........
Obviously higher means less drag and props actually can work better, sometimes, closer to the surface.
The Mercury site (i think) has pictures of motors with their cav plates clear of the water. As i am looking at getting other props it makes sense to make sure I have my current ones at their maximum performance/efficiency before introducing other things into the picture....

 

[gradyfish22]

I agree 100% about them being able to go higher, a lot of Grady's tests are done at the lowest mounting hole, if you look at Yamah's for the same boat they are higher, and Yamaha's results are typically better. Also, my 265 likes to run engines trimmed high, but it doesn't always like that running angle and sometimes does better with a little tab down, but I'm losing some efficiency by using the tab, if my engines were a hole higher I would probably have the best of both works but I am fairly happy with my performance overall and do not wish to invest the cash into fiddling with that right now. If I were going to buy new props I might consider going a hole higher as well from what I've notcied/experienced. As stated above, many Merc engines run very high and outperform Yamaha's for just that reason, for our boat design's though, going as high as some merc's are run might not be best, but going higher might benefit us if done in moderation. I agree 100% Grady is playing it super safe, they are a very conseravtive company, yes they do key in close to the right height, but consider that few of our boats are "stock" from the factory, we all customize them so none run identical, especially tho a factory boat so our numbers and theirs always differ.