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Well, now I'm ashamed. Today I made sure to find a straight piece of wood and verified with a level for the photo and it IS raised a little bit, about 20mm or 3/4 inch. Either the hull developed a hook from spending too much time on the trailer or I messed up the previous measurement!
I still think that my $80 prop isn't optimal, but I can admit that it's a bit raised now, let's see if the images will show
Its up a bit but, still relatively low. Your cav plate is probably total submerged while running. I suspect the ventilation is the props issue more then height. You could easily go up one hole on bracket. Maybe you can have someone run the boat while you look over the back at gearcase.
One your prop there is a big difference between a cheap new prop and an old been banged up numerous times and reconditioned a bunch.
How about a pic of the prop for grins?
Roller trailers have ruined many boats with hooks. Bunks are definitely better for the boat when the bunks extended just beyond transom.
The old propeller (Solas) that were on the boat when I bought it looked like it were part of the Jaws-movie, large chunks missing!
Current one is a Turning point 14-1/4x19 (part-no 21501911), new in box at a bargain price and now it got ~25 hours of runtime.
Before I looked at fuel, timing and linkage sync the AV plate were about ½ inch below water at roughly 37 knots and 5000 rpm (wouldnt rev more).
Now it's like the propeller does a burnout when cruising at that speed and giving it the beans :D Holeshot is good though!
That prop should work OK. Is the prop shaft bent? Is there something under boat forward of prop disturbing the water? What type of hub does the new prop have? Does the skeg have a twist in it? How much trim are you running underway? Does the boat respond to trim? I am not seeing anything to explain your issue.
I might just have to be satisfied with the current speed :leaving:
shaft is within tolerance, nothing besides a bit of texture in the paint on the hull between the bow and the motor, I’m even forcing the transducer to measure through it! Doesnt work too good at high speed or in rough sea.
The hub is made of rubber and skeg is damaged but not visibly twisted.
I don’t have a trim gauge installed, but the boat responds at lower speeds. Previous testing (at previous top speed) gave the impression of a light stern, wanting to blow out in corners if trimmed above neutral… I might have to borrow a gopro and record whats happening to learn more or just put more friends in the boat to see if I can use a larger prop :p
Keep your eye out for a laser II or a trophy plus in your pitch.
I can't overstate how much difference a nice prop will make.
Internet told me that the anti ventilation plate should be just above the surface at top speed, estimated how much I needed to raise the motor and its hard to see but it's in the white water now.
Got a short video of it, probably explains better than I can. 43 knots (49 mph) and 5600 RPM in the video, flat out singing :)
1. Should I raise it some more and see if it improves the bite of the propeller at high speed?
2. Is it worth trying before I get my hands on a good prop?
3. Anything else you can see thats worth to think of/try in the video?
https://youtu.be/vRSePI_Nc9U
PS: Todays testing "burned" off som paint on the prop, most likely from cavitation...
Yeah, raise the engine. The propeller shaft 4" below the boat would be good place to start.
If your prop has cavitation burns on it it isn't working and should be replaced. Your video suggests your engine is shall I say stock position. It is running negative trim as shown. The height is not causing the ventilation. Its not jacked at all as shown. Raising it more will not help it bit better.
@OnPad : Got pretty close to 4" below, but thats as high as I can get it without moving the bracket on the transom! Almost 40mm or about 1½ inch up from the video (total of 80mm from the pictures earlier).
@Jim Speros : All tips missing more paint than in the previous picture, can't think of anything else that might have caused it today. Yeah it doesn't like the having the lost ponies returned, I can easily get to 5600 rpm at 30 knots (37% slip) and just wait for the speed to build up slowly, untill it reaches 43 knots with a more reasonable 8% slip...
Video is raised 40mm from the first pictures, so it was truly submerged before! I thought I'd already passed the peak of mount stupid but my comments here might be the scream from falling down to the valley of despair (attached picture explains more) :p
I might have to install a trim gauge to get some repeatability in my testing, we were playing around up/down and it didnt like up/positive at all (loosing speed).
There is a 2nd hand Laser II for sale now, 21P instead of my current 19, should I go for it?
i expect that your low engine height is degrading your possible performance.Quote:
Originally Posted by OnPad
If you can only turn 19 5600 I would think 21 is too big. Hard to say for sure with your slip issue. Maybe you can get it to work with its bite and raising engine a little.
Nothing is worse then trying to spin a prop thats too big. Running an over propped boat is the worst.
@Jimboat : we will see if the weather allows another testrun tomorrow!
@Jim Speros : Its a carb motor with CDM ignition, isn't it limited to 5600? Thats what the sticker on my motor says too, so I assumed that was the case :O
There is a 2nd hand Laser II for sale now, 21P instead of my current 19, should I go for it?[/QUOTE]
I had a Laser 25p on a 16ft bass boat/150hp ran 65mph, and pulled over 6000rpm, but it was a 2.5L, and had a pad. The laser props are small diameter. I think 13 1/2". You should be able to pull a 21p laser no problem. If it doesn't work hang it in the garage, and justify it as a art collection, or precious metal,...That's my strategy.
I think those cdm carb engines do have a ignition cut rev limiter. That's going to make for a bigger art collection trying to maximize the setup of that hull. If not for the limiter that engine would be plenty happy at 6500rpm. Watch for a blown up older engine to rob the electrics off. Probably gain more that way vs prop swapping.
@OnPad: Have read some more in the service manual and its possible that the control module limit is 5900±100 for all engines regardless of specification. The saltwater is supposed to be a 2.5 so its just the modern safety stuff and conservative porting holding it back I guess.
65 mph is some serious speed imho! I’m trying to push around 6,5 meter or 21 feet (bow to transom), dont know the weight of just the boat but including the trailer its 1800 kg (almost 4000 lbs). Cheapest option might be to put a 2nd 150 on the boat :cheers:
Todays update: I managed to go for a fishing trip this evening after raising the motor as far as I could. No comments on the av plate due to the circumstances, however if I can trust my rpm gauge I picked up 200 rpm (5800 something) and lost 3 knots. Still got a healthy stream of cooling water out of the telltale, and a prop that doesnt feel connected to the water…
Tried to make a temporary trim gauge earlier by reading the resistance, but the sender were 100% ready for the bin (or, the remaining 50% of it)!