Hi all..i recently bought a 535c second hand and I think the engine is setup wrong somehow. 100hp mercury marine outboard 4 stroke.
I can't trim the engine above 0.9 without it porpoisong so steering is always pretty heavy.
Max revs was originally approx 5000 with top speed of 52km/h
Put a 4 blade prop on...it really helped with the porpoisong and was able to trim the engine right out at full throttle and steering was lovely...however revs now max out at 4750...max.speed 50km/h
I've seen a review where the same boat had a 90 suzuki on and they got 60km/h and apparently that boat had been tuned for rough waters....
I'm hoping someone can give me prop size and pitch on their 535c and will get some joy that way rather than just experimenting
Thanks in advance
Justin
Cant give you specific prop advice.
however, dont under estimate the affect if prop type on hull ride.
Not many people consider types of props they can run they only worry about pitch/blades which is a mistake
neutral lift, bow lift and stern lift props. especially within the merc range is immense and can make huge difference
That's interesting as I wouldn't have thought that changing the prop would stop porpoising. Usually a 4 blade is used for hole shot and it will reduce the rev range as well as top end speed.Originally Posted by Flex
One of the sad signs of our times is that we have demonized those who produce, subsidized those who refuse to produce and canonized those who complain.
Thomas Sowell
Generally 4 blades will lift the stern more and stop porpoising. but there are heaps of different types of 4 blades. Especially within the merc range. eg hi rake, low rake, larger diameter/smaller, cupping, blade geometry etc.
Plus you can get bow lifting 4 blades and stern lifitng 3 blades and visa-versa. generally 4 blade lift the stern more but not always
By the sounds you likely need a stern lifting prop and drop a pitch to make your boat ride flatter.
what prop do you run now?
also try re balancing your boat. move some weight forward if you can
Flex, Macca needs to reply as I've just only made a comment on 4 blade props. Sounds like there's been some big changes in props since I last investigated them.
One of the sad signs of our times is that we have demonized those who produce, subsidized those who refuse to produce and canonized those who complain.
Thomas Sowell
Check your motor height, too low a motor will cause porpoising.
I've been going through the same issue with a brand new boat, I've added 60kg to the bow, removed 30kg from the stern and lifted he motor 3 holes and it's a completely different boat.
Thabks for all the replies...is there an easy way to add pictures?
I added imgur links
You need to use the go advanced when posting pics mate.
It's hard to tell from those photos whether the motor is too low but when you're driving the boat have a look over the transom and see where the cav plate is sitting.
If you can't see the cav plate the motor is way too low.
What hole is the motor bolted on?
Ots on the 2nd hole from the top
It's hard to tell from those photos, the motor appears to be trimmed right in. Generally water will rise 1" for every foot past the hull (approx 25mm for every 300 mm, give or take) so you need to take that into consideration when working out heights, those with pods will understand. I don't have any experience with Bar Crushers but, not knowing your boating experience but do you trim the motor out when underway. I've seen too many who don't and often that's all that's needed to correct a lot of issues.
One of the sad signs of our times is that we have demonized those who produce, subsidized those who refuse to produce and canonized those who complain.
Thomas Sowell
Pretty new to boats but The problem is if I trim the boat slightly it porpoises....
I thought the motor looked too high but that could just be the photo and as BC's have a rear transom setup that I've never had anything to do with I'll leave it to BC owners to comment. Where abouts are you located, there should be someone with a BC around there. I'd hang around the ramps, I see them fairly regularly here at Golden Beach and talk to the owners.
One of the sad signs of our times is that we have demonized those who produce, subsidized those who refuse to produce and canonized those who complain.
Thomas Sowell
Boat is at gold coast.city marina...amc who I bought it off have been really good and said will send someone out on a trip with me to see what's happening. Thanks for all help
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