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1973 13' - how many holes up?
drewread	#1  Posted on 06/02/16 - 6:49 AM
Member Posts: 76 Comments: 0 Joined: 08/22/15	Well, I've just about done the planned work for this year on my 13' Whaler. I was looking to repower, but have decided to stick with what I have for this season... so I'd like to maximise this engine's potential if I can. It is running a 40hp Yamaha C40PLRU which I believe it is currently mounted what you would call 'one hole up.' Will I benefit from going 3 holes up (up to the top mounting hole), or will that be too high? Thanks for any advice! drewread attached the following image: [122.65Kb] Edited by drewread on 06/02/16 - 7:01 AM
tmann45	#2  Posted on 06/02/16 - 7:19 AM
Member Posts: 196 Comments: 0 Joined: 02/18/07	drewread wrote: It is running a 40hp Yamaha C40PLRU which I believe it is currently mounted what you would call 'one hole up.' Will I benefit from going 3 holes up (up to the top mounting hole), or will that be too high? From your picture it appears that you can't lower the motor due to the lower bolt is all the way up in the slot. Therefore I would say your motor is actually equivalent to 2-3 holes up already (looking at the distance between the bracket and the top of the transom). Take a look at your anti-ventilation plate when running, is it above or below the water? How high you can successfully run you motor depends on what prop you are using, some need to be fully submerged, others can run breaking the surface. What are your performance number now?
drewread	#3  Posted on 06/02/16 - 1:21 PM
Member Posts: 76 Comments: 0 Joined: 08/22/15	Am I not looking at moving the motor UP? In which case there are two more holes...?
Joe Kriz	#4  Posted on 06/02/16 - 1:30 PM
Site Owner Personal Page Personal Album Photo Albums Project Albums Posts: 11431 Comments: 452 Joined: 03/18/05	From what I see, you can lower the motor down one hole or go up 1 or 2 holes. Looks like you have the Standard mounting bolt pattern. At any rate, you would want to look at the cavitation plate when running on plane. You should be able to see the cavitation plate just at the water line or barely above so it is not creating a huge spray of water causing some "Drag".
drewread	#5  Posted on 06/02/16 - 5:18 PM
Member Posts: 76 Comments: 0 Joined: 08/22/15	OK, thanks. Perhaps I will throw a go-pro on the back tomorrow and have a look see.. hard to look back there while running top speed! ;)
drewread	#6  Posted on 06/03/16 - 1:50 PM
Member Posts: 76 Comments: 0 Joined: 08/22/15	tmann45 wrote: What are your performance number now? Had it out on a flat lake today, me and my 90lb dog - 31mph by dragonfly GPS. Silly me never looked at the tach, will do next time. I had a go-pro on the front and rear, we'll see if I got any decent footage of the motor, I didn't spend a lot of time aiming it ;)
drewread	#7  Posted on 06/04/16 - 11:13 AM
Member Posts: 76 Comments: 0 Joined: 08/22/15	and here is some video: https://youtu.be/AOERcdvLHqY The major spray from directly under the camera comes from a poorly placed Raymarine Dragonfly transducer.. that is a project for next week (If anyone has a suggested location for the transducer I'm willing to listen!) Will look at the tach today when flat out, but I'll have my family in the boat, so I expect top speed to be lower. ;)
tmann45	#8  Posted on 06/04/16 - 12:05 PM
Member Posts: 196 Comments: 0 Joined: 02/18/07	Joe Kriz wrote: From what I see, you can lower the motor down one hole or go up 1 or 2 holes. Looks like you have the Standard mounting bolt pattern. At any rate, you would want to look at the cavitation plate when running on plane. You should be able to see the cavitation plate just at the water line or barely above so it is not creating a huge spray of water causing some "Drag". After reading Joe's post and closer inspection of the photo, I believe Joe is correct, you have standard bolt pattern and are mounted 1-hole up. 31 MPH is not bad, about what I get with 35HP on a PT-35 and stainless prop. What prop are you running? And, check the tach! From your video it appears that you could try raising the motor.
Phil T	#9  Posted on 06/04/16 - 2:14 PM
Administrator Personal Page Personal Album Project Albums Posts: 6986 Comments: 6 Joined: 03/26/05	My brother had a similar setup with a C40, mounted 2 holes up, Yamaha painted stainless steel prop. I measured 33-34 mph running beside him. He was solo, no gear in choppy salt water conditions. It was a very uncomfortable ride for him.
drewread	#10  Posted on 06/05/16 - 1:11 PM
Member Posts: 76 Comments: 0 Joined: 08/22/15	Ok, for notation sake.. run with family in boat, 28.5mph (myself, wife and 2 kids - approx 525lbs?) at 5000rpm @ WOT
drewread	#11  Posted on 06/26/16 - 6:41 PM
Member Posts: 76 Comments: 0 Joined: 08/22/15	OK mounted all the way up now, will be heading out for a run tomorrow and will report specs. I figure I will either be churning a pile of air or will get some improvement in speed. ;) https://flic.kr/p/JuK32w