2001 282 outboards motor shaft length question
- Thread starter DBinSD
- Start date
What is the reasoning behind why you would want to do this? You'll have negative performance issues.
When I read the question, I originally though it was a kind of dumb question. If a 25 inch motor allowed the cavitation plate to be about level with the keel, a shorter shaft like a 20 would be 5 inches higher and that for a recreational hull would be just awful. It could also result in the motor overheating since the water inlets may not be under water BUT to fair some racing boat setups mount the motors with the cav plate pretty high over the water, 4 inches or so. That allows the hull to be trimmed at a steep angle at high speed. In some cases, the entire hull will be out of the water and the only thing in the water is the prop..
DBinSD
Member
How would I know without asking?
Having someone who has never done it, tell me it won’t work is not the input / knowledge I’m looking for. No offense.
There is clearly more experience on here than I have.
If someone says they HAD better results with a different length shaft. I WANT to know the WHY.
Well, I don't know how my experience compares to yours, but I've only been boating my whole life and worked in the industry for over 30 years
It's not hard to figure out the "why" without ever doing it - just like I've never added 234 plus 366... but I know that I can do it. It's drag and ventilation - just common sense. If you want someone to hold your hand, I'm the wrong guy - I expect people to do some thinking on their own. But I will be honest and upfront with you on everything. I did tell you, though, that it's a bad idea.Seasick - those race boats also use props that are actually designed to run partially above the water and they typically have water inlets mounted somewhere else, in better water, as opposed to the drive. Crazy stuff!
DBinSD
Member
You obviously have the throne on experience.Well, I don't know how my experience compares to yours, but I've only been boating my whole life and worked in the industry for over 30 years
Seasick - those race boats also use props that are actually designed to run partially above the water and they typically have water inlets mounted somewhere else, in better water, as opposed to the drive. Crazy stuff!
I never need my hand held, ever.
Saying “it’s a bad idea” provides ZERO information to myself or others seeking different input.
How about this way- What if someone used a slightly longer shaft, WHY is that bad for rough waters?
Well, if I can be a little sarcastic for a bit, but in a fun way... I already answered that
What happens when the drive sticks down lower in the water? You create more drag. If you're only ever going to go 5 mph, it'd be relatively inconsequential - but still worse. The effect gets worse and worse the faster you go. If you're continually ventilating, you're going too fast. So, yeah, you could use a jack plate to adjust the draft of the engine for minor improvements in some situations - but to go a full 5" all the time is no good. Unless you ONLY boat in rough weather at 5mph.
PointedRose
Well-Known Member
Most boat builders essentially standardized for the 25” shaft for a single engine setup on a boat about 18’ or more. Something other than that is more unusual, unless you have twin engines (or more). If twin engines on a v hull, the props sit higher than the lowest point of the v so would be 20’ but still below the hull line.
Smaller engines up to 25hp have variability in shaft length because they can be used on alums, inflatables, sailboats, etc that will have different transom heights.
Smaller engines up to 25hp have variability in shaft length because they can be used on alums, inflatables, sailboats, etc that will have different transom heights.
glacierbaze
Well-Known Member
I think Dennis' point is, that if you know why your boat is spec'ed for 25" drives, you should know why 20" or 30" would not improve anything. Some deep vees running 3 to 5 outboards run 30" in the center, and 25" on the outside, to keep the top of the motors even.
Some of the single DV's probably run 30", but the design would compensate on the mounting height, not on the prop depth.
Some of the single DV's probably run 30", but the design would compensate on the mounting height, not on the prop depth.