Motor height....need some expert advice

[walleyehed]

Re: Motor height....need some expert advice

Can you trim the motor all the way out or close to it without massive ventilation???<br />If you can, you still need to go up with the motor some...you'll gain more R's and speed.<br />Find the optimum set-up for the engine before waisting time swapping props.<br />Been there, done that.<br />BTW, the Trophy is a good prop but it won't do anymore than your 2+2 Turbo.

 

[walleyehed]

Re: Motor height....need some expert advice

currently 4300rpm (max trimmed all the way out) @ 54mph<br />

P.S. - I do also have a turbo 2+2 (4 blade) 13 3/4 x 26 which lowers the rpm by about 300 rpm and looses about 2 or 3 mph. So I am selling the turbo. <br />

These both tell me your engine is still not high enough.....the reason the Turbo drops in RPM is because it is a more efficient design on top of more pitch, which allows higher running heigth, which is what you want.

 

[spego]

Re: Motor height....need some expert advice

Well I do agree with you Walleyehed. The motor probably could go up more but goign back to the beginning with the fact it is a XL shaft it will look pretty weird on there if I keep goign up with it. It does not vent when trimmed back all the way....but yet the angel of the transom is quite steep so you don't get a lot of trim back out of it. I guess thats why the holeshot is so good with trimming it down all the way its tilted back under quite a way. But anyway I might be able to do another 1" up without it starting to look totally stupid but that may be it. Really the resolve would be to change the motor like we talked about before but this will have to do. So you don't think it will be worth getting rid of the prop then? Hang onto it?

 

[spego]

Re: Motor height....need some expert advice

Would goign up an inch make a big difference? I might do another inch but no more.

 

[walleyehed]

Re: Motor height....need some expert advice

1 inch "could" be 200 rpm...better than the max R's you're at now.<br />The Turbo hooks up good and if you can get some drag removed from the Lower unit and get the prop through the surface, you may see some speed rise as well.<br />One thing to watch for is cooling system water pressure with higher eng. heigth.<br />Make it look good, or make it perform.....the choice is yours.

 

[spego]

Re: Motor height....need some expert advice

Well let me try it then....worse case I can move it back down. I will try an inch or so (1/2 here or there) and see what it does. Next project!! LOL Let you know how I make out. Thanks

 

[KCLOST]

Re: Motor height....need some expert advice

spego,<br /><br />Like Walleyhed suggests, you should install a water pressure guage....

 

[spego]

Re: Motor height....need some expert advice

Yeah the boat has one on it. Well its not a gauge with numbers....its is Suzuki's digital gauge that show bars on the water level (pressure). Since my move the gauge really has not been effected much at all. But I am keeping a close eye on it and making sure the motor doesn't get hot.

 

[Winger Ed.]

Re: Motor height....need some expert advice

Originally posted by spego:<br />gauge that show bars on the water level (pressure).

That's good. It means you can still safely raise the engine a bit more. From looking at the pictures,,, your engine has rather high water pickups compared to a Merc. for example.<br />Since you're still in a very safe zone in relation to your rpm with your present prop.<br /> <br />If you really really want to tweek the last little bit of speed out of it:<br /><br />Keep raising the engine. When your water pressure falls off noticably at speed, block the top 1/2 inch or 1 inch of its intake holes, or let the engine back down an inch. If kept clean, the remaining holes will still let plenty of water in, provided you keep up with with maint. and always have a good healty water pump impeller.<br /><br />You could keep going up from there to get a little bit more, but you'd need to get into minor surgery in reguard to low water pickups like racing boats use. Which in your case, probably wouldn't be worth the time & trouble of fooling with.<br /><br />Ohh, I didn't want to get away without thanking you for sharing your endavors, and keeping us informed with the progress of this project. Not to mention the time you've spent working on it with (what I call)a 'make do' engine. Most folks who couldn't go down to the boat shop, whip out a credit card, and tell them to 'fix it', would have been content with hanging that extra long shaft on there and just living with it at 35 mph/3800rpm or whatever. <br /><br />And, using the arrow for a reference point was brilliant. It helped diagnois your situation better in 2 seconds, than trying to grasp 5 pages of dictionary size print trying to explain your situation could. <br /><br /><br />This thread has been a whole lot more interesting than discussing the finer points of rotted floors, transoms full of wet sawdust, and discussions of 'Why won't my boat start'? from someone with one posting, then you never see them again......<br /><br />...... which are good too, but this thread has been one of my favorites to watch and hopefully contribute to.<br /><br />Ed.

 

[spego]

Re: Motor height....need some expert advice

Well thats great. I am glad to hear that I have brought up something that interests everyone. You all have been a big help.<br /><br />

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<br /><br />Some measurements for you:<br /><br />V to propshaft - 5 3/4" (after I moved it 1" this morning)<br /><br />setback - 4 3/4"<br /><br />bolt size - 3/4" (installed this morning)<br /><br />center to center measurement of bolts on plate (side) - 8 1/2"<br /><br />bottom plate bolt (side) to top engine bolt - 16 3/4"<br /><br />transom top bolt to engine top bolt - 10 1/2" (total lift)<br /><br />plate length (boat side) - 19"<br /><br />plate legth (motor side) - 21"<br /><br /><br />Ok so I moved it up 1 inch and it ran faster and got about 5000 - 5050 rpm out of it. It was hard to hold it there though. The wind was blowing and it was getting up under the boat and causing ti walk and plus I was running it with only myself in it. I seemed to be uneven and chine walked at the high end.<br /><br />But anyway I got 5000 (maybe 5050) @ 58mph<br /><br />I might be able to get more but like I said I think I would need a calmer day. I am going to try the 3 blade next time though.....should get more rpm out of it and the boat should stay down in the water a little further.<br /><br />I still cannot get the prop to blow out at full tilt but it now shoots a big tail and starts to loose a little speed so I trimmed it back in and it was good.<br /><br />I could let you know how the 3 blade works sometime during the week.

 

[Winger Ed.]

Re: Motor height....need some expert advice

I'd say you're about there. <br />For a regular working boat, I think you've just about run out of horsepower to get much more speed out of it for the weight you're carrying and hull design. If it was a tunnel hull or a Molinari, you might get a little more since the boat lifts up out of the water with air pressure.<br /><br />You can tinker around with different props and get your rpm up a little, but the trade off in increased speed will probably be all but un-noticable. Since you aren't racing it, the next few weeks spent struggling with moving the engine up another inch or two, dealing low water pickups, nose cones, etc. may or may not be worth another 6mph to ya. At least not until we talk about having your cyl. heads cut, and other such mods.. LOL...<br /><br /><br />All in all,,,,<br />That's a good looking set up. And running about 60 is a rush ain't it? At most places, you'd start running out of lake pretty quick. <br />Ed.

 

[walleyehed]

Re: Motor height....need some expert advice

I believe you have met the max speed the hull design will allow without some help. In particular, Smart Tabs....<br />My boat is a foot and a half longer than yours with the same hull design, and for fear of being "found out", I'm not gonna tell ya how much HP I've got on the transom, but I will tell you it's over 100HP more than max recommended.<br />My point is 60MPH is great, and at those speeds, I've found the smart tabs to be the ONLY thing that lets me remain in control, "cruising" at 60...<br />EDIT: I should add I use the "Mobster Tabs" by Nauticus, (makers of smart tabs)due to the speeds exceeding 70MPH, such that would be used on Bass boats.

 

[spego]

Re: Motor height....need some expert advice

Yeah I was thinking the same....probably all I am getting. Which is totally fine by me. If I can cruise at 45 or 50 that is awesome. I dont need much you know....like Ed said it doesn't take long to run out of lake at close to 60 anyway unless your on a finger lake or great lakes.....but I don't visit them too much anyway. I might some day think abotu smart tabs but not right now I don't think I will mess with them. Would for sure fix the problem. I will try out the 3 blade prop this week and see what that looks like and see what to do from there. I am assuming the 3 blade will put me at about 5300 or 5400 rpm. I should be good there. So this issue may be just about solved!! (woo hoo!! lol) Now let me see....whats next. lol

 

[Winger Ed.]

Re: Motor height....need some expert advice

53-5400 is good. For a work-a-day fishing boat, you've got good speed, decent fuel economy for the size engine & hull, and you can get where ya want to go in reasonable amount of time. Plus, you can out run all but the biggest of the water lice(jetskis).<br /><br />And, at 5400, the engine is doing what it was designed to do, and it will keep doing that for many years to come, and unlike the guy that runs along at 8-10,000 rpm,,,,,, getting a extra 12 mph...<br /><br />You won't have to think to yourself----<br />Gosh, the engine has almost 10 hours on it,,,, I need to order gaskets and rings again, so I can ovewrhaul this thing next weekend......

 

[walleyehed]

Re: Motor height....need some expert advice

Winger, I never made it past 7 hrs.....How do you get 10????????????

 

[Winger Ed.]

Re: Motor height....need some expert advice

Originally posted by walleyehed:<br /> Winger, I never made it past 7 hrs.....How do you get 10????????????

......<br /><br />Buy the cheapest, oldest, and most foul smelling gas you can find ---- like I do. <br /><br />It pops and sputters a bit, but hey!!, I do get 3 extra hours on the Hobbs meter before I need a overhaul.

 

[spego]

Re: Motor height....need some expert advice

Just to let you guys know.<br /><br />I ran the 3 blade....the motor is up too high now for the 3 blade to catch. It ran 5800 @ 51 mph and shot a hell of a tail behind it. I am leaving everything be I think and putting the 4 blade back on there. 5000 is in the range it should operate at (per Suzuki manual 5000-5600) and the speed is the best I have gotten so far. I may next year think about sending the prop to a shop and having them tweek it a bit to see if they can get the R's up more (will loose some of the speed though). So problem solved I guess.

 

[spego]

Re: Motor height....need some expert advice

Well that brings me back to another question....monster tabs were brought up. Do they cause drag at top speed? will they knock off mph? Christmas is coming up and I was considering asking for smart tabs (189) or monster tabs (229) but I do not want them if they are going to shave off the top end. Hell I can back off to 55 or 56 and not chine walk at all and really that would be one of the main reasons I would want them.

 

[Jdeagro]

Re: Motor height....need some expert advice

spego;<br /><br />They are called MOBster Tabs (Steal The Hole) meaning that they will make the boat accelerate faster, plane faster, ride cleaner and increase top end. <br /><br />Your Boat should run about 62 MPH and turn about 5400 to 5500 RPMs. Obviously your have been on the right track in getting the motor up higher, but don't kid yourself about the SE Sport Foil being up out of the water at speed. It is still lifting the back. The splash of the water at speed is producing a lot of water pressure (like a fire hose) on the foil. This is lifting the stern and forcing you to trim the motor up too much just to get the bow up. The extra stern lift ( at speeds) is a disadvantage to speed. And it does not take much to scrub off three or four MPH. <br /><br />Take the foil off ( I know you will loose your hole shot ) and see if the boat runs faster - it is easy to do. If it does ( assuming the boat does not porpoise and chine walk too much) then call me and we will work on getting the stability and speed up to 60+. (800-233-0194)<br /><br />All this aside you should remember that "bass boat don't need trim tabs" (ask any of the boat dealers) and you would be considered "odd" having them on your boat. Even if they do allow you to run faster and smoother. Just a little sarcasm! Sorry! I hear it all the time! <br /><br />The short story is that a properly balanced hull with make the boat accelerate faster, run smoother, and get more top speed. The hull effeciency is more important than the horse power.

 

[spego]

Re: Motor height....need some expert advice

I might be taking it out fishing tomorrow. I might just do that to try it. I will let you know the results. Thanks