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Location: Not far enough north! | Heres a question...
I run an esox magnum with a fifty fourstroke tiller. It gets me up about 30mph WOT the hole shot is not good. Its got a vengance 14 p prop on it I think( Will check tomorrow) I know props can make a huge difference but was thinking about re powering with a 60. One dealer I talked to said that I would not see enough of a difference to make it worth the money. I kind of find that hard to believe... What are your thoughts?
Rick |
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| I run a 1700 Osprey with a 70 HP 4 stroke on it. I get about 30 mph WOT. I know that a 90 HP 4 stroke only pushes the same hull about 6-8 MPH faster. I would assume it would be very similar numbers in your case as well. |
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Posts: 2323
Location: Stevens Point, WI | Rick, in this case, the dealer is correct. However, the 14 Vengeance prop is absolutely to big. For that rig, you should have either a 11 Vengeance for really good hole shot or a 12 for the best top end speed. The 50 and 60 hp motors are built on the same block so you wouldn't see a whole lot of difference. |
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Location: Not far enough north! | TJ,
I will check the prop tomorrow for sure its at the farm. I know the blocks are the same size you have to go to a 75 for the next size up but they can do alot with cylinder size in a block. I will check the displacement between the two sizes to see if its just a carb difference... I imagine the EFI on the newer engines would make a difference too.
Thanks
Rick |
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Posts: 1663
Location: Kodiak, AK | As far as repowering being worth it, it depends on why you're doing it. If it's for the sake of more speed, I'd say no and to mess with set up and enjoy whatever gains you get. But if you're repowering because you've got a motor issue now and you want to keep the boat long into the future, then yes, absolutely it's worth it. But if your motor is sound, even if you want to run the hull forever, wait until you need to repower. I don't think repowering for the sake of rewpowering would often, if ever make financial sense.
I repowered in the spring of 09 because my motor blew, it was going to cost more to rebuild it than it was worth running, and mostly because I plan to be buried in this boat when I die. I bought a new motor and I'm only more and more happy with my decision. |
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Posts: 3479
Location: Elk River, Minnesota | Hiya,
In most cases, an increase of 1 mph is roughly equivalent to an increase in about 10hp given all things are the same. Engine displacement can help with low end torque and a little more "umph" felt while accelerating...but as for top speed, all are pretty close to being the same.
I would agree that if your hole shot is slow, you are over-pitched on your prop. If memory serves me correctly, that motor has at lowest a 2:1 gear ratio but I would guess it is more around a 1.85:1 gear ratio. The closer the two numbers are in the ratio, the smaller the pitch one needs to get good overall performance...especially out of the hole...top end not so much. So...your 14 pitch, I would say is probably about 2 - 3 inches too much, with a 12 being solid potential. On that rig, I would also not be surprised if a 10 would do really well also.
Friend of mine has a 50 4 stroke yamaha on an older model Alumacraft Dominator (way way way underpowered) and runs an 11 pitch which does alright. He sees about 26 mph.
So...repower for a couple thousand and an extra mph maybe and a little better hole shot, or re-pitch for around $150 to get your hole shot and maybe a loss of 1 - 2mph on top end?
I, myself would take the hole shot over speed, because if you get into a blow, having the low end power to the engine is much more valuable...especially in following seas. the ability to drive up a wave to avoid swamping from the rear is a HUGE benefit to have.
Steve
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Location: Not far enough north! | Well the prop is a 14. Which is what I thought. I also did some checking and rpms should run between 5500 and 6000 at WOT. I dont pay that much attention but I think I'm getting around 5000 to 5100. However I do not know how accurate the tach is on the boat. I am not that concerned with top speed too much but I think going to a smaller prop and gaining those rpms I'd probably not lose any top end but improve the hole shot...
There is nothing wrong with the engine and is very solid. So if there is not much to gain your right it would not be worth the money at all. Thats why these forums are so valuable. I'm starting to like this dealer a little more he could have easily said that a 60 would have made a difference and tried to sell me one... I guess I'll start looking at props. Im sure there have been some vast improvements in the last ten years.
Thanks
Rick |
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Posts: 158
| I'm not sure on the 4 stroked, but on two strokes, when an engine uses the same block, it usually has the same displacement. They make the extra HP with port changes and carb changes.
I wouldn't be surprised if a 60hp 4stroke had the same exact displacement as the 50hp 4stroke. A simple engine swap would see very little in the way of hole shot performance increase in this case. |
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Posts: 32880
Location: Rhinelander, Wisconsin | Wrong prop for sure. You need an 11 or 12. |
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50hp to 60hp