Ventalation problem

[walleyehed]

Re: Ventalation problem

Lowering pitch is the last step we want to take...this causes a loss of total efficiency..and we don't need to drop pitch if the hole-shot is good and the WOT, normal load is at the top of the RPM range...slightly above is even better. No reason to cut the top if we have the bottom......

 

[npd4432]

Re: Ventalation problem

Lowering pitch is the last step we want to take...this causes a loss of total efficiency..and we don't need to drop pitch if the hole-shot is good and the WOT, normal load is at the top of the RPM range...slightly above is even better. No reason to cut the top if we have the bottom......

The RPM range for the motor is 5200-5800 rpm max. The boat with the 13 pitch is WOT about 6000-6100 rpm. I keep a good eye on it and rarely let it go over 5800, so I would not want to go any lower on the pitch, the hole shot is good and top speed is OK for what I use the boat for. The 13.75 dia. looks like it is the maximum I can go with as the clearance is minimal with the vent plate. I think a 14 would strike the plate, I would hate to see that, I will take pics of that too. This is why I have a hard time with the prop, the turning point hustler in the 13 pitch is 14" Dia. as are most.

The boat when I bought it came with a standard issue OMC 15 pitch 13.75 dia prop. The vent problem was the same but the boat would barely pull me out of the water when skiing, and when I mean barely I am talking about dragging for a good 75 yards.

 

[npd4432]

Re: Ventalation problem

First, let me add that at 13.75" diameter, this is slightly SMALLER than std diameter for the V4 JohnRude. Most of the OMC/BRP's in 13P for the 13 spline will be 14" diameter for 13 pitch.
One "slightly" dinged blade can cause the problems you have....so can a missing piece (even small) of gel-coat on the hull.
If I were to look into a prop, I'd say you'd have as good of luck with an aluminum OMC/BRP 14X13, as you would any aluminum.
Now, if you think you might want to go SS, I'd shoot for a Stiletto 13.25X13P, but we need to make sure there isn't something from the hull causing a vent pocket first.

The prop itself is in great shape, no dings. I have used it for two seasons of fairly heavy use. The motor is not a V4 it is a 75 HP inline 3 looper. I will get some pics up as soon as I get to my lake house. Give me a few days.

 

[MikDee]

Re: Ventalation problem

I don't see anything else wrong with your setup? I still say your prop design, & diameter, is too big causing the problem, here is a reasonable prop from iboats that seems more like what you need, I don't know if it has 13 splines, or if that's specific to your motor? It's made for a 3cyl 75hp thru-prop exhaust, 1975 up to 1985 though, and, if you read the review right there, it says "Great in turn's, better then the stock prop" also going to a 1 1/4" smaller diam. prop might mean you need more pitch too:
http://www.boat-props.com/propeller..._id=59&**********=835395197&*******=323132850

By the way, I have a 19' Bowrider with a 125hp outboard, and a 13"X19" 3 blade alum. prop, a heavier load, with more power then you, and it's fine, not loosing anything with the smaller diameter!

 

[walleyehed]

Re: Ventalation problem

Should be the exact distance, whether a V4 or 3cyl...they both use the same props on the 13 spline shafts with 4" gearcases.
14" props should run with plenty of clearance....in fact, I'll bet you your engine it will work.
To add another note here, just because diameter or pitch changes, does NOT mean we need to go up or down with the other...todays props are built with a higher tech level that takes pitch/diameter into account within the design, yet you can have a 14X17P built for stern-lift and low speed, the same demensions as an over-all lifter or bow-lifter.
The blade area and design may change, but the pitch and diameter may not. Mis-application is 99% of the prop trouble most people/dealers have.

 

[npd4432]

Re: Ventalation problem

The last two posts by Mikdee and Walleyhed bring up an intresting point. The propfinder area of Iboats has two types of 75 HP applications, one for "75HP thru hub exhaust" the one Mikdee recommended and "75HP thru hub exhaust pleasure 13 tooth spline" As Walleyhed stated a 14" dia prop should run with plenty clearance. My 13.75 does not have alot at all. Do I possibly have the wrong prop on the wrong gearcase?

Which is the proper application?? the "75HP thru hub exhaust" or the "75HP thru hub exhaust pleasure 13 tooth spline"

I am going to the lake tomorrow to snap pics, hopefully this will shed some light to the problem.

My motor is a 1983 Evinrude 75 HP model E75TRLCTE.

 

[walleyehed]

Re: Ventalation problem

Count the splines on your prop-shaft.
If it's an '83 it has 13 splines.

The Solas Amita in 13.75" diameter in 13 pitch is P/N 2411-138-13. This is for 13 spline prop-shafts....same as the V4's use, and your lower unit will handle a 14" diameter prop if needed.

 

[npd4432]

Re: Ventalation problem

here are the pics.

 

[walleyehed]

Re: Ventalation problem

Plenty of room for a 14" prop...but I don't think that's the issue as low as the engine is...that prop just lacks any significant cup...you need to go to a higher tech design.

 

[npd4432]

Re: Ventalation problem

Would the Turning Point Hustler be a good choice? any other recommendations??

 

[guy74]

Re: Ventalation problem

Count the splines on your prop-shaft.
If it's an '83 it has 13 splines.

The Solas Amita in 13.75" diameter in 13 pitch is P/N 2411-138-13. This is for 13 spline prop-shafts....same as the V4's use, and your lower unit will handle a 14" diameter prop if needed.

A 14 inch prop wouldn't fit on my 1988 60hp Johnson without clearancing the trim tab. I have ran a 13 3/4 X 15, and a 14 X 13 Turning Point Hustler props on my 60hp, both with good results. The Hustler props realy held on to the water, and were alot harder to make ventilate than the factory OMC props.

 

[npd4432]

Re: Ventalation problem

I am leaning toward the 14X13 Turning Point Hustler, but am open to other suggestions.

 

[guy74]

Re: Ventalation problem

My Glastron V156 with a 60hp Johnson was a little under propped with the 14X13 Hustler prop. (WOT of 6250-6350 @ 28mph). Made it pull really good when pulling up a skier, but really drank gas trying to pull at skiing speed. I settled on the 13 3/4X15 hustler prop, after I ported it, it performed as well as I could expect ( WOT 5900 @ 34mph). Shoot me a PM if you want more details on my experience with those props.

 

[walleyehed]

Re: Ventalation problem

"A 14 inch prop wouldn't fit on my 1988 60hp Johnson without clearancing the trim tab."

Not a real problem there...notch the tab.
You don't mention the prop that wouldn't fit, but the 14" is not the problem, apparently Rake was.
Watch the slip ratio on the hustler...it might bite but the design lacks efficiency. The cup is not placed correctly for some reason. Every one of these I have tested showed high slip numbers.....I don't care for them, and there isn't many props I haven't run in aluminum.
If they've changed the design of the Hustler, maybe it's getting better, but the 2007 stock I ran pulled hard, just didn't produce the speed for the drop in RPM....

 

[guy74]

Re: Ventalation problem

"A 14 inch prop wouldn't fit on my 1988 60hp Johnson without clearancing the trim tab."

Not a real problem there...notch the tab.
You don't mention the prop that wouldn't fit, but the 14" is not the problem, apparently Rake was.
Watch the slip ratio on the hustler...it might bite but the design lacks efficiency. The cup is not placed correctly for some reason. Every one of these I have tested showed high slip numbers.....I don't care for them, and there isn't many props I haven't run in aluminum.
If they've changed the design of the Hustler, maybe it's getting better, but the 2007 stock I ran pulled hard, just didn't produce the speed for the drop in RPM....

The diameter was the problem, I had to clearance the bace of the trim tab. Everyone talks as if the 3cylinder and V4 J/E LUs are the same, but the V4 unit is longer from the ventilation plate to the prop shaft, it also has a longer skeg. At least those are the differences between the 2 I have ('88 60hp & '89 100hp). The 14x13 Hustler had very little rake, more of a high thrust design with large rounded blades. As far as slip ratio, and efficiency I would guess you are right on the money with those comments. I feel that I got the performance that I paid for, the Hustler props were the lowest priced props I could find here on Iboats at the time.

 

[walleyehed]

Re: Ventalation problem

The distance on these 2 units should be the same...they are both 20" shaft models and if they were different, the AV plate would not match-up the same. You could install a 70, or a 90 and the AV plate is in the same location. They both are 20" shafts, so the prop is in the same location, unless it's an older non 13 spline....then the gearcase is different and so is the prop.

 

[guy74]

Re: Ventalation problem

The distance on these 2 units should be the same...they are both 20" shaft models and if they were different, the AV plate would not match-up the same. You could install a 70, or a 90 and the AV plate is in the same location. They both are 20" shafts, so the prop is in the same location, unless it's an older non 13 spline....then the gearcase is different and so is the prop.

I went out and measured the two I have in the shed, a 1988 60hp johnson(3 cylinder) and a 1989 100hp evinrude (V4). The distances from the AV plate are: 6 15/16" (3 cyl), and 7 1/4" (V4). Also measured from the AV plate to the bottom of the skeg 14 1/2" (3 cyl), and 15 3/4" (V4). I really have no good way to measure the "shaft length", but as I noted when I changed between these two motors on my boat, the V4's AV plate is about a 1/4" lower when placed parallel to the bottom of the boat. That is with both motors in the top holes (as low as I can mount them). I'm not trying to be agumentative here, but as I said the 14" props wouldn't fit the 3 cyl LU without relieving the base of the trim tab, or at least they won't fit mine.

 

[walleyehed]

Re: Ventalation problem

You could verywell be correct..Last year I ran 3 MWC props on a 70hp...1 was a 14X17...and there were no clearance issues. I ran the exact three props on a Suzuki 115 and a Johnson 115 looper with hub kits for each engine.

Here's some P/N's..and apps..
This is for 45-75hp thru-hub 13 spline shafts...from 1971-up.
ALL 9 P/N's for OMC 2 and 3cyl engines are the EXACT P/N's listed for all V4 thru-hub 13 spline (V4 case) for 85-140hp.
Of those listed, there is a 14X11, 14X13, 14X17, 14X19, and a 14X21.
That's from OMC.
MWC lists 7 pitches in 14" diameter for the same engines.
Also, according to my OMC book, the only way those 2 dimensions could be different on the lower unit is that the one measuring 6-15/16 is the 1985 and older thru-hub lower unit. The 1988 60hp measures the same as the V4.

I would have to question your trim tab....the base should be flush with bottom of AV plate, but it may be the wrong lower unit....

 

[guy74]

Re: Ventalation problem

Also, according to my OMC book, the only way those 2 dimensions could be different on the lower unit is that the one measuring 6-15/16 is the 1985 and older thru-hub lower unit. The 1988 60hp measures the same as the V4.

I would have to question your trim tab....the base should be flush with bottom of AV plate, but it may be the wrong lower unit....

My 1988 60hp has the original LU on it, but that doesn't mean it wasn't assembled with an older LU from the factory. The trim tab is correct and flush with the bottom of the AV plate. I don't know how to explain the differences that I have, but I do know that when I slide either of the 14" dia. props I have on the 60hp they hit the trim tab. I know all the catalogs call for 14" props for that motor, but sometimes catalogs are wrong. The pictures from the member who started this thread, showing his LU with a 13 3/4" dia prop, the clearance on that prop look identical to mine with that size prop. He might have trouble fitting a 14" dia. prop too, thats the only reason I included my info. Upon further research, it would seem that mechanical shift, 3 cyl gearcases are divided at the 1988-89 model change. Maybe a 14" prop fits on the later gearcase without any problems, I don't have one to measure.

 

[walleyehed]

Re: Ventalation problem

I've got a customer here with a 70hp Johnson but I wasn't sure of the year...it's an '87 on a 15ft+ Glastron...he's running a 14X17 on it...
It doesn't turn the RPM I've told him it should, but you can lead a horse to water...bla, bla, bla...etc...
The only problems I've had were with the older small gearcase 2's and 3's...they swing a prop in the 11-13" range...
I wish I had a better answer to why you had the tab problem, but I'm using the OEM and aftermarket books for reference, and I sell props as a part of my living...I've had no issues with the intermediate gearcase. It's one of those areas where you just learn the applications...I can't say for sure why this isn't the case with yours.