Chipping / Mapping Boat Engines
Discussion
minimax said:
i'm not much help, but I do want to ask: why are boat engines so low powered? comparitively that is to cars?
How many forward gears does your average boat have, comparatively that is to cars ?You need a flat enough torque curve to enable the prop to pull throughout the rev range unless you want to start talking about variable pitch props, pretty much unheard of in leisure boating.
You can tune your engine for increased power at the top end sure, but if that comes at a loss of low end torques such that the prop will stall the engine at anything less than 20 knots, then getting back into your marina berth is going to be fun.
Edited by Seight_Returns on Friday 5th September 22:22
Quite happy to admit that I know nothing about engines and chipping/modding.......however....
How is the prop driven? by a reduction gearbox or direct drive?
Increasing power will presumably increase prop RPM? I would wonder at what rotational speed the propeller will start to cavitate? I guess its not much over the prop RPM at current max power. You may require a new propeller after you have modded your engine as you could find that you have decreased your powertrain output capability.
How is the prop driven? by a reduction gearbox or direct drive?
Increasing power will presumably increase prop RPM? I would wonder at what rotational speed the propeller will start to cavitate? I guess its not much over the prop RPM at current max power. You may require a new propeller after you have modded your engine as you could find that you have decreased your powertrain output capability.
Well I would assume that it's quite a different beast to a car engine. Possibly the same case, heads, pistons etc, but would imagine the cams and compression are specific to the application. Specifically I guess it doesn't need the low down torque in this application and engine life is more important than out and out power. Presumably it spends a fair amount of time at constant RPM and has a completely different cooling system also.
None of that means it can't be tuned, but I'd be wary of using an automotive engine map!
None of that means it can't be tuned, but I'd be wary of using an automotive engine map!
schmalex said:
Also tell him to look at surface piercing props or just simply changing the prop diameter. Surface piercing props are a lot more efficient than sunk props & will boost performance a lot more than chipping
The problem is a surface drive increases top speed but greatly reduces acceleration - probably not what he wants in a loaded boat in the solent.Edited by schmalex on Friday 5th September 22:23
Seight_Returns said:
minimax said:
i'm not much help, but I do want to ask: why are boat engines so low powered? comparitively that is to cars?
How many forward gears does your average boat have, comparatively that is to cars ?You need a flat enough torque curve to enable the prop to pull throughout the rev range unless you want to start talking about variable pitch props, pretty much unheard of in leisure boating.
You can tune your engine for increased power at the top end sure, but if that comes at a loss of low end torques such that the prop will stall the engine at anything less than 20 knots, then getting back into your marina berth is going to be fun.
Edited by Seight_Returns on Friday 5th September 22:22
[quote=minimax]i'm not much help, but I do want to ask: why are boat engines so low powered? comparitively that is to cars?
For longevity & reliability. If the engine in your car breaks down on a wet, windy night - inconvenient. If you are 20 miles from land in a gale and the engine in your boat stops - nasty.
For longevity & reliability. If the engine in your car breaks down on a wet, windy night - inconvenient. If you are 20 miles from land in a gale and the engine in your boat stops - nasty.
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